[jira] [Commented] (FOP-2847) [PATCH] Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16802799#comment-16802799
]
Tobias Hain commented on FOP-2847:
--
[~ssteiner1] here you go:
https://github.com/apache/fop/pull/55
All other three removed from open pull request list.
> [PATCH] Support palette-based transparency via tRNS chunk of PNG images in
> PDF export
> -
>
> Key: FOP-2847
> URL: https://issues.apache.org/jira/browse/FOP-2847
> Project: FOP
> Issue Type: Bug
> Components: renderer/pdf
>Affects Versions: 2.3
>Reporter: Tobias Hain
>Priority: Major
> Attachments: acrobat_reader_error_message.PNG,
> broken_generated_pdf.pdf, pal_bk.png, pdf_trans_broken.png,
> sample_image_palette_tRNS.png
>
>
> h4. TL;NR
> When using palette-based transparency via tRNS chunk in PNG images, the
> generated PDFs are broken.
> h4. palette-based with transparency.
> {quote}*8.5.2. Palette-Based with Transparency*
> "The PNG spec forbids the use of a full alpha channel with palette-based
> images, but it does allow `cheap alpha` via the transparency chunk, tRNS
> [...] In effect, it transforms the palette from an RGB lookup table to an
> RGBA table [...] a single PNG transparency entry should come first"
> {quote}
> [http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
> h4. general PDF encoding strategy
> Option 1:
> {quote}most libraries just undo the palettization and use a full color image
> + mask.
> {quote}
> [https://forums.adobe.com/message/6148131#6148131]
> Option 2:
> {quote}SMask would be simpler since you could leave the palette in place
> {quote}
> [https://forums.adobe.com/message/6148557#6148557]
> h4. what does FOP do
> It creates a chroma-key mask:
> {code:java}
> /Type /XObject
> /ColorSpace [/Indexed /DeviceRGB 255 ]
> /Mask [182 182 151 151 158 158]
> {code}
> Acrobat Reader even fails to read those files while PDF viewers embedded into
> Chrome/Firefox read the file, but show visual glitches:
> !acrobat_reader_error_message.PNG!
> https://github.com/apache/fop/pull/49 fixes the Acrobat Reader error.
> FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to
> do that:
> [https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
> In fact the following results in missing Option 2:
> {code:java}
> public void setup(PDFDocument doc) {
> RenderedImage ri = getImage().getRenderedImage();
> // code deleted
> Raster raster = GraphicsUtil.getAlphaRaster(ri);
> if (raster != null) {
> AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
> raster);
> this.softMask = doc.addImage(null, alphaImage).makeReference();
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
> In the above code raster will be null and therefore FOP fails to initialize a
> softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
> {{ColorModel.getAlphaRaster()}}, which returns null:
> {quote}If this is an IndexColorModel which has alpha in the lookup table,
> this method will return null since there is no spatially discrete alpha
> channel.
> {quote}
> [https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html]
> The softMask Issue is fixed by:
> https://github.com/apache/fop/pull/50
> As a result an image such as !pal_bk.png! is rendered with a transparency
> gradient instead of !pdf_trans_broken.png!
> This code will then add the chroma key mask to the image:
> {code:java}
> protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary
> dict, IndexColorModel icm) {
> // code deleted
> Integer index = getIndexOfFirstTransparentColorInPalette(icm);
> if (index != null) {
> PDFArray mask = new PDFArray(dict);
> mask.add(index);
> mask.add(index);
> dict.put("Mask", mask);
> }
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java]
> h4. why care to support?
> Libraries such as pngquant optimize images for web usage and low footprint
> and can not be used directly with Apache FOP as source images:
> {quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8
> bit color palette with dithering. It will build indexed-color PNG's with
> alpha transparency colors conveyed in the tRNS chunk."
> {quote}
> [https://imagemagick.org/Usage/formats/#png_non-im]
> h4. sample data
> {code}
> $ identify -verbose sample_image_palette_tRNS.png
> Format: PNG (Portable Network Graphics)
> Type: PaletteAlpha
> png:IHDR.color_type : 3 (Indexed)
> png:tRNS : chunk was found
>
[jira] [Comment Edited] (FOP-2847) [PATCH] Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16794974#comment-16794974
]
Tobias Hain edited comment on FOP-2847 at 3/24/19 8:29 PM:
---
{quote}Can you add a unit test{quote}
[~ssteiner1] Added unit tests, please review and pull. Three different pull
requests, since issues are actually unrelated.
{code:java}
https://github.com/apache/fop/pull/50
+ FOP-2847: fix PNGs with index color model did not render SMask
https://github.com/apache/fop/pull/49
+ FOP-2847: fix Mask for PNG with IndexColorModel and transparent color
+ depends on pull#50 since it shares some mock data. Due to rebase pull/49
incorporates pull/50 - so just pull this one.
https://github.com/apache/fop/pull/51
+ FOP-2847: optimize memory footprint when rendering images with IndexC…
+ trivial without side effects: no unit test required
{code}
The tests are written such that the same test is performed with the same image,
but different colorspace models. Some of the tests will pass FOP trunk to also
demonstrate the expected behavior (e.g. PNGs with ARGB will work fine already
on FOP trunk). The pull request fixes this for other colorspace models.
was (Author: 7oby):
{quote}Can you add a unit test{quote}
[~ssteiner1] Added unit tests, please review and pull. Three different pull
requests, since issues are actually unrelated.
{code:java}
https://github.com/apache/fop/pull/50
+ FOP-2847: fix PNGs with index color model did not render SMask
https://github.com/apache/fop/pull/49
+ FOP-2847: fix Mask for PNG with IndexColorModel and transparent color
+ depends on pull#50 since it shares some mock data
https://github.com/apache/fop/pull/51
+ FOP-2847: optimize memory footprint when rendering images with IndexC…
+ trivial without side effects: no unit test required
{code}
> [PATCH] Support palette-based transparency via tRNS chunk of PNG images in
> PDF export
> -
>
> Key: FOP-2847
> URL: https://issues.apache.org/jira/browse/FOP-2847
> Project: FOP
> Issue Type: Bug
> Components: renderer/pdf
>Affects Versions: 2.3
>Reporter: Tobias Hain
>Priority: Major
> Attachments: acrobat_reader_error_message.PNG,
> broken_generated_pdf.pdf, pal_bk.png, pdf_trans_broken.png,
> sample_image_palette_tRNS.png
>
>
> h4. TL;NR
> When using palette-based transparency via tRNS chunk in PNG images, the
> generated PDFs are broken.
> h4. palette-based with transparency.
> {quote}*8.5.2. Palette-Based with Transparency*
> "The PNG spec forbids the use of a full alpha channel with palette-based
> images, but it does allow `cheap alpha` via the transparency chunk, tRNS
> [...] In effect, it transforms the palette from an RGB lookup table to an
> RGBA table [...] a single PNG transparency entry should come first"
> {quote}
> [http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
> h4. general PDF encoding strategy
> Option 1:
> {quote}most libraries just undo the palettization and use a full color image
> + mask.
> {quote}
> [https://forums.adobe.com/message/6148131#6148131]
> Option 2:
> {quote}SMask would be simpler since you could leave the palette in place
> {quote}
> [https://forums.adobe.com/message/6148557#6148557]
> h4. what does FOP do
> It creates a chroma-key mask:
> {code:java}
> /Type /XObject
> /ColorSpace [/Indexed /DeviceRGB 255 ]
> /Mask [182 182 151 151 158 158]
> {code}
> Acrobat Reader even fails to read those files while PDF viewers embedded into
> Chrome/Firefox read the file, but show visual glitches:
> !acrobat_reader_error_message.PNG!
> https://github.com/apache/fop/pull/49 fixes the Acrobat Reader error.
> FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to
> do that:
> [https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
> In fact the following results in missing Option 2:
> {code:java}
> public void setup(PDFDocument doc) {
> RenderedImage ri = getImage().getRenderedImage();
> // code deleted
> Raster raster = GraphicsUtil.getAlphaRaster(ri);
> if (raster != null) {
> AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
> raster);
> this.softMask = doc.addImage(null, alphaImage).makeReference();
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
> In the above code raster will be null and therefore FOP fails to initialize a
> softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
> {{ColorModel.getAlphaRaster()}}, which returns null:
> {quote}If this is an IndexColorModel which has alpha in the lookup table,
> this method will return null since there is no spatially discrete alpha
>
[jira] [Comment Edited] (FOP-2847) [PATCH] Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16794974#comment-16794974
]
Tobias Hain edited comment on FOP-2847 at 3/23/19 11:08 PM:
{quote}Can you add a unit test{quote}
[~ssteiner1] Added unit tests, please review and pull. Three different pull
requests, since issues are actually unrelated.
{code:java}
https://github.com/apache/fop/pull/50
+ FOP-2847: fix PNGs with index color model did not render SMask
https://github.com/apache/fop/pull/49
+ FOP-2847: fix Mask for PNG with IndexColorModel and transparent color
+ depends on pull#50 since it shares some mock data
https://github.com/apache/fop/pull/51
+ FOP-2847: optimize memory footprint when rendering images with IndexC…
+ trivial without side effects: no unit test required
{code}
was (Author: 7oby):
{quote}Can you add a unit test\{quote}
[~ssteiner1]: Yes, just give me a couple of days to find a time slot to do so.
> [PATCH] Support palette-based transparency via tRNS chunk of PNG images in
> PDF export
> -
>
> Key: FOP-2847
> URL: https://issues.apache.org/jira/browse/FOP-2847
> Project: FOP
> Issue Type: Bug
> Components: renderer/pdf
>Affects Versions: 2.3
>Reporter: Tobias Hain
>Priority: Major
> Attachments: acrobat_reader_error_message.PNG,
> broken_generated_pdf.pdf, pal_bk.png, pdf_trans_broken.png,
> sample_image_palette_tRNS.png
>
>
> h4. TL;NR
> When using palette-based transparency via tRNS chunk in PNG images, the
> generated PDFs are broken.
> h4. palette-based with transparency.
> {quote}*8.5.2. Palette-Based with Transparency*
> "The PNG spec forbids the use of a full alpha channel with palette-based
> images, but it does allow `cheap alpha` via the transparency chunk, tRNS
> [...] In effect, it transforms the palette from an RGB lookup table to an
> RGBA table [...] a single PNG transparency entry should come first"
> {quote}
> [http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
> h4. general PDF encoding strategy
> Option 1:
> {quote}most libraries just undo the palettization and use a full color image
> + mask.
> {quote}
> [https://forums.adobe.com/message/6148131#6148131]
> Option 2:
> {quote}SMask would be simpler since you could leave the palette in place
> {quote}
> [https://forums.adobe.com/message/6148557#6148557]
> h4. what does FOP do
> It creates a chroma-key mask:
> {code:java}
> /Type /XObject
> /ColorSpace [/Indexed /DeviceRGB 255 ]
> /Mask [182 182 151 151 158 158]
> {code}
> Acrobat Reader even fails to read those files while PDF viewers embedded into
> Chrome/Firefox read the file, but show visual glitches:
> !acrobat_reader_error_message.PNG!
> https://github.com/apache/fop/pull/49 fixes the Acrobat Reader error.
> FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to
> do that:
> [https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
> In fact the following results in missing Option 2:
> {code:java}
> public void setup(PDFDocument doc) {
> RenderedImage ri = getImage().getRenderedImage();
> // code deleted
> Raster raster = GraphicsUtil.getAlphaRaster(ri);
> if (raster != null) {
> AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
> raster);
> this.softMask = doc.addImage(null, alphaImage).makeReference();
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
> In the above code raster will be null and therefore FOP fails to initialize a
> softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
> {{ColorModel.getAlphaRaster()}}, which returns null:
> {quote}If this is an IndexColorModel which has alpha in the lookup table,
> this method will return null since there is no spatially discrete alpha
> channel.
> {quote}
> [https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html]
> The softMask Issue is fixed by:
> https://github.com/apache/fop/pull/50
> As a result an image such as !pal_bk.png! is rendered with a transparency
> gradient instead of !pdf_trans_broken.png!
> This code will then add the chroma key mask to the image:
> {code:java}
> protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary
> dict, IndexColorModel icm) {
> // code deleted
> Integer index = getIndexOfFirstTransparentColorInPalette(icm);
> if (index != null) {
> PDFArray mask = new PDFArray(dict);
> mask.add(index);
> mask.add(index);
> dict.put("Mask", mask);
> }
> }
> {code}
>
[jira] [Commented] (FOP-2847) [PATCH] Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16794974#comment-16794974
]
Tobias Hain commented on FOP-2847:
--
{quote}Can you add a unit test\{quote}
[~ssteiner1]: Yes, just give me a couple of days to find a time slot to do so.
> [PATCH] Support palette-based transparency via tRNS chunk of PNG images in
> PDF export
> -
>
> Key: FOP-2847
> URL: https://issues.apache.org/jira/browse/FOP-2847
> Project: FOP
> Issue Type: Bug
> Components: renderer/pdf
>Affects Versions: 2.3
>Reporter: Tobias Hain
>Priority: Major
> Attachments: acrobat_reader_error_message.PNG,
> broken_generated_pdf.pdf, pal_bk.png, pdf_trans_broken.png,
> sample_image_palette_tRNS.png
>
>
> h4. TL;NR
> When using palette-based transparency via tRNS chunk in PNG images, the
> generated PDFs are broken.
> h4. palette-based with transparency.
> {quote}*8.5.2. Palette-Based with Transparency*
> "The PNG spec forbids the use of a full alpha channel with palette-based
> images, but it does allow `cheap alpha` via the transparency chunk, tRNS
> [...] In effect, it transforms the palette from an RGB lookup table to an
> RGBA table [...] a single PNG transparency entry should come first"
> {quote}
> [http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
> h4. general PDF encoding strategy
> Option 1:
> {quote}most libraries just undo the palettization and use a full color image
> + mask.
> {quote}
> [https://forums.adobe.com/message/6148131#6148131]
> Option 2:
> {quote}SMask would be simpler since you could leave the palette in place
> {quote}
> [https://forums.adobe.com/message/6148557#6148557]
> h4. what does FOP do
> It creates a chroma-key mask:
> {code:java}
> /Type /XObject
> /ColorSpace [/Indexed /DeviceRGB 255 ]
> /Mask [182 182 151 151 158 158]
> {code}
> Acrobat Reader even fails to read those files while PDF viewers embedded into
> Chrome/Firefox read the file, but show visual glitches:
> !acrobat_reader_error_message.PNG!
> https://github.com/apache/fop/pull/49 fixes the Acrobat Reader error.
> FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to
> do that:
> [https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
> In fact the following results in missing Option 2:
> {code:java}
> public void setup(PDFDocument doc) {
> RenderedImage ri = getImage().getRenderedImage();
> // code deleted
> Raster raster = GraphicsUtil.getAlphaRaster(ri);
> if (raster != null) {
> AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
> raster);
> this.softMask = doc.addImage(null, alphaImage).makeReference();
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
> In the above code raster will be null and therefore FOP fails to initialize a
> softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
> {{ColorModel.getAlphaRaster()}}, which returns null:
> {quote}If this is an IndexColorModel which has alpha in the lookup table,
> this method will return null since there is no spatially discrete alpha
> channel.
> {quote}
> [https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html]
> The softMask Issue is fixed by:
> https://github.com/apache/fop/pull/50
> As a result an image such as !pal_bk.png! is rendered with a transparency
> gradient instead of !pdf_trans_broken.png!
> This code will then add the chroma key mask to the image:
> {code:java}
> protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary
> dict, IndexColorModel icm) {
> // code deleted
> Integer index = getIndexOfFirstTransparentColorInPalette(icm);
> if (index != null) {
> PDFArray mask = new PDFArray(dict);
> mask.add(index);
> mask.add(index);
> dict.put("Mask", mask);
> }
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java]
> h4. why care to support?
> Libraries such as pngquant optimize images for web usage and low footprint
> and can not be used directly with Apache FOP as source images:
> {quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8
> bit color palette with dithering. It will build indexed-color PNG's with
> alpha transparency colors conveyed in the tRNS chunk."
> {quote}
> [https://imagemagick.org/Usage/formats/#png_non-im]
> h4. sample data
> {code}
> $ identify -verbose sample_image_palette_tRNS.png
> Format: PNG (Portable Network Graphics)
> Type: PaletteAlpha
> png:IHDR.color_type : 3 (Indexed)
> png:tRNS : chunk was found
[jira] [Updated] (FOP-2847) Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Tobias Hain updated FOP-2847:
-
Attachment: pal_bk.png
> Support palette-based transparency via tRNS chunk of PNG images in PDF export
> -
>
> Key: FOP-2847
> URL: https://issues.apache.org/jira/browse/FOP-2847
> Project: FOP
> Issue Type: Bug
> Components: renderer/pdf
>Affects Versions: 2.3
>Reporter: Tobias Hain
>Priority: Major
> Attachments: acrobat_reader_error_message.PNG,
> broken_generated_pdf.pdf, pal_bk.png, pdf_trans_broken.png,
> sample_image_palette_tRNS.png
>
>
> h4. TL;NR
> When using palette-based transparency via tRNS chunk in PNG images, the
> generated PDFs are broken.
> h4. palette-based with transparency.
> {quote}*8.5.2. Palette-Based with Transparency*
> "The PNG spec forbids the use of a full alpha channel with palette-based
> images, but it does allow `cheap alpha` via the transparency chunk, tRNS
> [...] In effect, it transforms the palette from an RGB lookup table to an
> RGBA table [...] a single PNG transparency entry should come first"
> {quote}
> [http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
> h4. general PDF encoding strategy
> Option 1:
> {quote}most libraries just undo the palettization and use a full color image
> + mask.
> {quote}
> [https://forums.adobe.com/message/6148131#6148131]
> Option 2:
> {quote}SMask would be simpler since you could leave the palette in place
> {quote}
> [https://forums.adobe.com/message/6148557#6148557]
> h4. what does FOP do
> It creates a chroma-key mask:
> {code:java}
> /Type /XObject
> /ColorSpace [/Indexed /DeviceRGB 255 ]
> /Mask [182 182 151 151 158 158]
> {code}
> Acrobat Reader even fails to read those files while PDF viewers embedded into
> Chrome/Firefox read the file, but show visual glitches:
> !acrobat_reader_error_message.PNG!
> FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to
> do that:
> [https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
> In fact the following results in missing Option 2:
> {code:java}
> public void setup(PDFDocument doc) {
> RenderedImage ri = getImage().getRenderedImage();
> // code deleted
> Raster raster = GraphicsUtil.getAlphaRaster(ri);
> if (raster != null) {
> AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
> raster);
> this.softMask = doc.addImage(null, alphaImage).makeReference();
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
> In the above code raster will be null and therefore FOP fails to initialize a
> softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
> {{ColorModel.getAlphaRaster()}}, which returns null:
> {quote}If this is an IndexColorModel which has alpha in the lookup table,
> this method will return null since there is no spatially discrete alpha
> channel.
> {quote}
> [https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html]
> This code will then add the chroma key mask to the image:
> {code:java}
> protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary
> dict, IndexColorModel icm) {
> // code deleted
> Integer index = getIndexOfFirstTransparentColorInPalette(icm);
> if (index != null) {
> PDFArray mask = new PDFArray(dict);
> mask.add(index);
> mask.add(index);
> dict.put("Mask", mask);
> }
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java]
> h4. why care to support?
> Libraries such as pngquant optimize images for web usage and low footprint
> and can not be used directly with Apache FOP as source images:
> {quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8
> bit color palette with dithering. It will build indexed-color PNG's with
> alpha transparency colors conveyed in the tRNS chunk."
> {quote}
> [https://imagemagick.org/Usage/formats/#png_non-im]
> h4. sample data
> {code}
> $ identify -verbose sample_image_palette_tRNS.png
> Format: PNG (Portable Network Graphics)
> Type: PaletteAlpha
> png:IHDR.color_type : 3 (Indexed)
> png:tRNS : chunk was found
> {code}
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[jira] [Updated] (FOP-2847) Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Tobias Hain updated FOP-2847:
-
Description:
h4. TL;NR
When using palette-based transparency via tRNS chunk in PNG images, the
generated PDFs are broken.
h4. palette-based with transparency.
{quote}*8.5.2. Palette-Based with Transparency*
"The PNG spec forbids the use of a full alpha channel with palette-based
images, but it does allow `cheap alpha` via the transparency chunk, tRNS [...]
In effect, it transforms the palette from an RGB lookup table to an RGBA table
[...] a single PNG transparency entry should come first"
{quote}
[http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
h4. general PDF encoding strategy
Option 1:
{quote}most libraries just undo the palettization and use a full color image +
mask.
{quote}
[https://forums.adobe.com/message/6148131#6148131]
Option 2:
{quote}SMask would be simpler since you could leave the palette in place
{quote}
[https://forums.adobe.com/message/6148557#6148557]
h4. what does FOP do
It creates a chroma-key mask:
{code:java}
/Type /XObject
/ColorSpace [/Indexed /DeviceRGB 255 ]
/Mask [182 182 151 151 158 158]
{code}
Acrobat Reader even fails to read those files while PDF viewers embedded into
Chrome/Firefox read the file, but show visual glitches:
!acrobat_reader_error_message.PNG!
https://github.com/apache/fop/pull/49 fixes the Acrobat Reader error.
FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to do
that:
[https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
In fact the following results in missing Option 2:
{code:java}
public void setup(PDFDocument doc) {
RenderedImage ri = getImage().getRenderedImage();
// code deleted
Raster raster = GraphicsUtil.getAlphaRaster(ri);
if (raster != null) {
AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
raster);
this.softMask = doc.addImage(null, alphaImage).makeReference();
}
{code}
[https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
In the above code raster will be null and therefore FOP fails to initialize a
softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
{{ColorModel.getAlphaRaster()}}, which returns null:
{quote}If this is an IndexColorModel which has alpha in the lookup table, this
method will return null since there is no spatially discrete alpha channel.
{quote}
[https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html]
The softMask Issue is fixed by:
https://github.com/apache/fop/pull/50
As a result an image such as !pal_bk.png! is rendered with a transparency
gradient instead of !pdf_trans_broken.png!
This code will then add the chroma key mask to the image:
{code:java}
protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary dict,
IndexColorModel icm) {
// code deleted
Integer index = getIndexOfFirstTransparentColorInPalette(icm);
if (index != null) {
PDFArray mask = new PDFArray(dict);
mask.add(index);
mask.add(index);
dict.put("Mask", mask);
}
}
{code}
[https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java]
h4. why care to support?
Libraries such as pngquant optimize images for web usage and low footprint and
can not be used directly with Apache FOP as source images:
{quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8 bit
color palette with dithering. It will build indexed-color PNG's with alpha
transparency colors conveyed in the tRNS chunk."
{quote}
[https://imagemagick.org/Usage/formats/#png_non-im]
h4. sample data
{code}
$ identify -verbose sample_image_palette_tRNS.png
Format: PNG (Portable Network Graphics)
Type: PaletteAlpha
png:IHDR.color_type : 3 (Indexed)
png:tRNS : chunk was found
{code}
was:
h4. TL;NR
When using palette-based transparency via tRNS chunk in PNG images, the
generated PDFs are broken.
h4. palette-based with transparency.
{quote}*8.5.2. Palette-Based with Transparency*
"The PNG spec forbids the use of a full alpha channel with palette-based
images, but it does allow `cheap alpha` via the transparency chunk, tRNS [...]
In effect, it transforms the palette from an RGB lookup table to an RGBA table
[...] a single PNG transparency entry should come first"
{quote}
[http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
h4. general PDF encoding strategy
Option 1:
{quote}most libraries just undo the palettization and use a full color image +
mask.
{quote}
[https://forums.adobe.com/message/6148131#6148131]
Option 2:
{quote}SMask would be simpler since you could leave the palette in place
{quote}
[https://forums.adobe.com/message/6148557#6148557]
h4. what does FOP
[jira] [Updated] (FOP-2847) Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Tobias Hain updated FOP-2847:
-
Attachment: pdf_trans_broken.png
> Support palette-based transparency via tRNS chunk of PNG images in PDF export
> -
>
> Key: FOP-2847
> URL: https://issues.apache.org/jira/browse/FOP-2847
> Project: FOP
> Issue Type: Bug
> Components: renderer/pdf
>Affects Versions: 2.3
>Reporter: Tobias Hain
>Priority: Major
> Attachments: acrobat_reader_error_message.PNG,
> broken_generated_pdf.pdf, pal_bk.png, pdf_trans_broken.png,
> sample_image_palette_tRNS.png
>
>
> h4. TL;NR
> When using palette-based transparency via tRNS chunk in PNG images, the
> generated PDFs are broken.
> h4. palette-based with transparency.
> {quote}*8.5.2. Palette-Based with Transparency*
> "The PNG spec forbids the use of a full alpha channel with palette-based
> images, but it does allow `cheap alpha` via the transparency chunk, tRNS
> [...] In effect, it transforms the palette from an RGB lookup table to an
> RGBA table [...] a single PNG transparency entry should come first"
> {quote}
> [http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
> h4. general PDF encoding strategy
> Option 1:
> {quote}most libraries just undo the palettization and use a full color image
> + mask.
> {quote}
> [https://forums.adobe.com/message/6148131#6148131]
> Option 2:
> {quote}SMask would be simpler since you could leave the palette in place
> {quote}
> [https://forums.adobe.com/message/6148557#6148557]
> h4. what does FOP do
> It creates a chroma-key mask:
> {code:java}
> /Type /XObject
> /ColorSpace [/Indexed /DeviceRGB 255 ]
> /Mask [182 182 151 151 158 158]
> {code}
> Acrobat Reader even fails to read those files while PDF viewers embedded into
> Chrome/Firefox read the file, but show visual glitches:
> !acrobat_reader_error_message.PNG!
> FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to
> do that:
> [https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
> In fact the following results in missing Option 2:
> {code:java}
> public void setup(PDFDocument doc) {
> RenderedImage ri = getImage().getRenderedImage();
> // code deleted
> Raster raster = GraphicsUtil.getAlphaRaster(ri);
> if (raster != null) {
> AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
> raster);
> this.softMask = doc.addImage(null, alphaImage).makeReference();
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
> In the above code raster will be null and therefore FOP fails to initialize a
> softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
> {{ColorModel.getAlphaRaster()}}, which returns null:
> {quote}If this is an IndexColorModel which has alpha in the lookup table,
> this method will return null since there is no spatially discrete alpha
> channel.
> {quote}
> [https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html]
> This code will then add the chroma key mask to the image:
> {code:java}
> protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary
> dict, IndexColorModel icm) {
> // code deleted
> Integer index = getIndexOfFirstTransparentColorInPalette(icm);
> if (index != null) {
> PDFArray mask = new PDFArray(dict);
> mask.add(index);
> mask.add(index);
> dict.put("Mask", mask);
> }
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java]
> h4. why care to support?
> Libraries such as pngquant optimize images for web usage and low footprint
> and can not be used directly with Apache FOP as source images:
> {quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8
> bit color palette with dithering. It will build indexed-color PNG's with
> alpha transparency colors conveyed in the tRNS chunk."
> {quote}
> [https://imagemagick.org/Usage/formats/#png_non-im]
> h4. sample data
> {code}
> $ identify -verbose sample_image_palette_tRNS.png
> Format: PNG (Portable Network Graphics)
> Type: PaletteAlpha
> png:IHDR.color_type : 3 (Indexed)
> png:tRNS : chunk was found
> {code}
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[jira] [Updated] (FOP-2847) Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Tobias Hain updated FOP-2847:
-
Description:
h4. TL;NR
When using palette-based transparency via tRNS chunk in PNG images, the
generated PDFs are broken.
h4. palette-based with transparency.
{quote}*8.5.2. Palette-Based with Transparency*
"The PNG spec forbids the use of a full alpha channel with palette-based
images, but it does allow `cheap alpha` via the transparency chunk, tRNS [...]
In effect, it transforms the palette from an RGB lookup table to an RGBA table
[...] a single PNG transparency entry should come first"
{quote}
[http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
h4. general PDF encoding strategy
Option 1:
{quote}most libraries just undo the palettization and use a full color image +
mask.
{quote}
[https://forums.adobe.com/message/6148131#6148131]
Option 2:
{quote}SMask would be simpler since you could leave the palette in place
{quote}
[https://forums.adobe.com/message/6148557#6148557]
h4. what does FOP do
It creates a chroma-key mask:
{code:java}
/Type /XObject
/ColorSpace [/Indexed /DeviceRGB 255 ]
/Mask [182 182 151 151 158 158]
{code}
Acrobat Reader even fails to read those files while PDF viewers embedded into
Chrome/Firefox read the file, but show visual glitches:
!acrobat_reader_error_message.PNG!
FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to do
that:
[https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
In fact the following results in missing Option 2:
{code:java}
public void setup(PDFDocument doc) {
RenderedImage ri = getImage().getRenderedImage();
// code deleted
Raster raster = GraphicsUtil.getAlphaRaster(ri);
if (raster != null) {
AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
raster);
this.softMask = doc.addImage(null, alphaImage).makeReference();
}
{code}
[https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
In the above code raster will be null and therefore FOP fails to initialize a
softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
{{ColorModel.getAlphaRaster()}}, which returns null:
{quote}If this is an IndexColorModel which has alpha in the lookup table, this
method will return null since there is no spatially discrete alpha channel.
{quote}
[https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html]
This code will then add the chroma key mask to the image:
{code:java}
protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary dict,
IndexColorModel icm) {
// code deleted
Integer index = getIndexOfFirstTransparentColorInPalette(icm);
if (index != null) {
PDFArray mask = new PDFArray(dict);
mask.add(index);
mask.add(index);
dict.put("Mask", mask);
}
}
{code}
[https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java]
h4. why care to support?
Libraries such as pngquant optimize images for web usage and low footprint and
can not be used directly with Apache FOP as source images:
{quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8 bit
color palette with dithering. It will build indexed-color PNG's with alpha
transparency colors conveyed in the tRNS chunk."
{quote}
[https://imagemagick.org/Usage/formats/#png_non-im]
h4. sample data
{code}
$ identify -verbose sample_image_palette_tRNS.png
Format: PNG (Portable Network Graphics)
Type: PaletteAlpha
png:IHDR.color_type : 3 (Indexed)
png:tRNS : chunk was found
{code}
was:
h4. TL;NR
When using palette-based transparency via tRNS chunk in PNG images, the
generated PDFs are broken.
h4. palette-based with transparency.
{quote}*8.5.2. Palette-Based with Transparency*
"The PNG spec forbids the use of a full alpha channel with palette-based
images, but it does allow `cheap alpha` via the transparency chunk, tRNS [...]
In effect, it transforms the palette from an RGB lookup table to an RGBA table
[...] a single PNG transparency entry should come first"
{quote}
[http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
h4. general PDF encoding strategy
Option 1:
{quote}most libraries just undo the palettization and use a full color image +
mask.
{quote}
[https://forums.adobe.com/message/6148131#6148131]
Option 2:
{quote}SMask would be simpler since you could leave the palette in place
{quote}
[https://forums.adobe.com/message/6148557#6148557]
h4. what does FOP do
It creates a chroma-key mask:
{code:java}
/Type /XObject
/ColorSpace [/Indexed /DeviceRGB 255 ]
/Mask [182 182 151 151 158 158]
{code}
Acrobat Reader even fails to read those files while PDF viewers embedded into
Chrome/Firefox read the file, but
[jira] [Updated] (FOP-2847) Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Tobias Hain updated FOP-2847:
-
Attachment: acrobat_reader_error_message.PNG
> Support palette-based transparency via tRNS chunk of PNG images in PDF export
> -
>
> Key: FOP-2847
> URL: https://issues.apache.org/jira/browse/FOP-2847
> Project: FOP
> Issue Type: Bug
> Components: renderer/pdf
>Affects Versions: 2.3
>Reporter: Tobias Hain
>Priority: Major
> Attachments: acrobat_reader_error_message.PNG,
> broken_generated_pdf.pdf, sample_image_palette_tRNS.png
>
>
> h4. TL;NR
> When using palette-based transparency via tRNS chunk in PNG images, the
> generated PDFs are broken.
> h4. palette-based with transparency.
> {quote}*8.5.2. Palette-Based with Transparency*
> "The PNG spec forbids the use of a full alpha channel with palette-based
> images, but it does allow `cheap alpha` via the transparency chunk, tRNS
> [...] In effect, it transforms the palette from an RGB lookup table to an
> RGBA table [...] a single PNG transparency entry should come first"
> {quote}
> [http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
> h4. general PDF encoding strategy
> Option 1:
> {quote}most libraries just undo the palettization and use a full color image
> + mask.
> {quote}
> [https://forums.adobe.com/message/6148131#6148131]
> Option 2:
> {quote}SMask would be simpler since you could leave the palette in place
> {quote}
> [https://forums.adobe.com/message/6148557#6148557]
> h4. what does FOP do
> It creates a chroma-key mask:
> {code:java}
> /Type /XObject
> /ColorSpace [/Indexed /DeviceRGB 255 ]
> /Mask [182 182 151 151 158 158]
> {code}
> Acrobat Reader even fails to read those files while PDF viewers embedded into
> Chrome/Firefox read the file, but show visual glitches.
> FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to
> do that:
> [https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
> In fact the following results in missing Option 2:
> {code:java}
> public void setup(PDFDocument doc) {
> RenderedImage ri = getImage().getRenderedImage();
> // code deleted
> Raster raster = GraphicsUtil.getAlphaRaster(ri);
> if (raster != null) {
> AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
> raster);
> this.softMask = doc.addImage(null, alphaImage).makeReference();
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
> In the above code raster will be null and therefore FOP fails to initialize a
> softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
> {{ColorModel.getAlphaRaster()}}, which returns null:
> {quote}If this is an IndexColorModel which has alpha in the lookup table,
> this method will return null since there is no spatially discrete alpha
> channel.
> {quote}
> [https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html]
> This code will then add the chroma key mask to the image:
> {code:java}
> protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary
> dict, IndexColorModel icm) {
> // code deleted
> Integer index = getIndexOfFirstTransparentColorInPalette(icm);
> if (index != null) {
> PDFArray mask = new PDFArray(dict);
> mask.add(index);
> mask.add(index);
> dict.put("Mask", mask);
> }
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java]
> h4. why care to support?
> Libraries such as pngquant optimize images for web usage and low footprint
> and can not be used directly with Apache FOP as source images:
> {quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8
> bit color palette with dithering. It will build indexed-color PNG's with
> alpha transparency colors conveyed in the tRNS chunk."
> {quote}
> [https://imagemagick.org/Usage/formats/#png_non-im]
> h4. sample data
> {code}
> $ identify -verbose sample_image_palette_tRNS.png
> Format: PNG (Portable Network Graphics)
> Type: PaletteAlpha
> png:IHDR.color_type : 3 (Indexed)
> png:tRNS : chunk was found
> {code}
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
[jira] [Updated] (FOP-2847) Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Tobias Hain updated FOP-2847:
-
Attachment: broken_generated_pdf.pdf
> Support palette-based transparency via tRNS chunk of PNG images in PDF export
> -
>
> Key: FOP-2847
> URL: https://issues.apache.org/jira/browse/FOP-2847
> Project: FOP
> Issue Type: Bug
> Components: renderer/pdf
>Affects Versions: 2.3
>Reporter: Tobias Hain
>Priority: Major
> Attachments: broken_generated_pdf.pdf, sample_image_palette_tRNS.png
>
>
> h4. TL;NR
> When using palette-based transparency via tRNS chunk in PNG images, the
> generated PDFs are broken.
> h4. palette-based with transparency.
> {quote}*8.5.2. Palette-Based with Transparency*
> "The PNG spec forbids the use of a full alpha channel with palette-based
> images, but it does allow `cheap alpha` via the transparency chunk, tRNS
> [...] In effect, it transforms the palette from an RGB lookup table to an
> RGBA table [...] a single PNG transparency entry should come first"
> {quote}
> [http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
> h4. general PDF encoding strategy
> Option 1:
> {quote}most libraries just undo the palettization and use a full color image
> + mask.
> {quote}
> [https://forums.adobe.com/message/6148131#6148131]
> Option 2:
> {quote}SMask would be simpler since you could leave the palette in place
> {quote}
> [https://forums.adobe.com/message/6148557#6148557]
> h4. what does FOP do
> It creates a chroma-key mask:
> {code:java}
> /Type /XObject
> /ColorSpace [/Indexed /DeviceRGB 255 ]
> /Mask [182 182 151 151 158 158]
> {code}
> Acrobat Reader even fails to read those files while PDF viewers embedded into
> Chrome/Firefox read the file, but show visual glitches.
> FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to
> do that:
> [https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
> In fact the following results in missing Option 2:
> {code:java}
> public void setup(PDFDocument doc) {
> RenderedImage ri = getImage().getRenderedImage();
> // code deleted
> Raster raster = GraphicsUtil.getAlphaRaster(ri);
> if (raster != null) {
> AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
> raster);
> this.softMask = doc.addImage(null, alphaImage).makeReference();
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
> In the above code raster will be null and therefore FOP fails to initialize a
> softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
> {{ColorModel.getAlphaRaster()}}, which returns null:
> {quote}If this is an IndexColorModel which has alpha in the lookup table,
> this method will return null since there is no spatially discrete alpha
> channel.
> {quote}
> [https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html]
> This code will then add the chroma key mask to the image:
> {code:java}
> protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary
> dict, IndexColorModel icm) {
> // code deleted
> Integer index = getIndexOfFirstTransparentColorInPalette(icm);
> if (index != null) {
> PDFArray mask = new PDFArray(dict);
> mask.add(index);
> mask.add(index);
> dict.put("Mask", mask);
> }
> }
> {code}
> [https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java]
> h4. why care to support?
> Libraries such as pngquant optimize images for web usage and low footprint
> and can not be used directly with Apache FOP as source images:
> {quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8
> bit color palette with dithering. It will build indexed-color PNG's with
> alpha transparency colors conveyed in the tRNS chunk."
> {quote}
> [https://imagemagick.org/Usage/formats/#png_non-im]
> h4. sample data
> {code}
> $ identify -verbose sample_image_palette_tRNS.png
> Format: PNG (Portable Network Graphics)
> Type: PaletteAlpha
> png:IHDR.color_type : 3 (Indexed)
> png:tRNS : chunk was found
> {code}
--
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[jira] [Created] (FOP-2847) Support palette-based transparency via tRNS chunk of PNG images in PDF export
Tobias Hain created FOP-2847:
Summary: Support palette-based transparency via tRNS chunk of PNG
images in PDF export
Key: FOP-2847
URL: https://issues.apache.org/jira/browse/FOP-2847
Project: FOP
Issue Type: Bug
Components: renderer/pdf
Affects Versions: 2.3
Reporter: Tobias Hain
h4. TL;NR
When using palette-based transparency via tRNS chunk in PNG images, the
generated PDFs are broken.
h4. palette-based with transparency.
{quote}*8.5.2. Palette-Based with Transparency*
"The PNG spec forbids the use of a full alpha channel with palette-based
images, but it does allow `cheap alpha` via the transparency chunk, tRNS [...]
In effect, it transforms the palette from an RGB lookup table to an RGBA table
[...] a single PNG transparency entry should come first"{quote}
http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2
h4. general PDF encoding strategy
Option 1:
{quote}most libraries just undo the palettization and use a full color image +
mask.{quote}
https://forums.adobe.com/message/6148131#6148131
Option 2:
{quote}SMask would be simpler since you could leave the palette in place{quote}
https://forums.adobe.com/message/6148557#6148557
h4. what does FOP do
It creates a chroma-key mask:
{code}
/Type /XObject
/ColorSpace [/Indexed /DeviceRGB 255 ]
/Mask [182 182 151 151 158 158]
{code}
Acrobat Reader even fails to read those files while PDF viewers embedded into
Chrome/Firefox read the file, but show visual glitches.
FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to do
that:
https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG
In fact the following results in missing Option 2:
{code}
public void setup(PDFDocument doc) {
RenderedImage ri = getImage().getRenderedImage();
// code deleted
Raster raster = GraphicsUtil.getAlphaRaster(ri);
if (raster != null) {
AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
raster);
this.softMask = doc.addImage(null, alphaImage).makeReference();
}
{code}
https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java
In the above code raster will be null and therefore FOP fails to initialize a
softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
{{ColorModel.getAlphaRaster()}}, which returns null:
{quote}If this is an IndexColorModel which has alpha in the lookup table, this
method will return null since there is no spatially discrete alpha
channel.{quote}
https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html
This code will then add the chroma key mask to the image:
{code}
protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary dict,
IndexColorModel icm) {
// code deleted
Integer index = getIndexOfFirstTransparentColorInPalette(icm);
if (index != null) {
PDFArray mask = new PDFArray(dict);
mask.add(index);
mask.add(index);
dict.put("Mask", mask);
}
}
{code}
https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java
h4. why care to support?
Libraries such as pngquant optimize images for web usage and low footprint and
can not be used directly with Apache FOP as source images:
{quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8 bit
color palette with dithering. It will build indexed-color PNG's with alpha
transparency colors conveyed in the tRNS chunk."{quote}
https://imagemagick.org/Usage/formats/#png_non-im
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[jira] [Updated] (FOP-2847) Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Tobias Hain updated FOP-2847:
-
Description:
h4. TL;NR
When using palette-based transparency via tRNS chunk in PNG images, the
generated PDFs are broken.
h4. palette-based with transparency.
{quote}*8.5.2. Palette-Based with Transparency*
"The PNG spec forbids the use of a full alpha channel with palette-based
images, but it does allow `cheap alpha` via the transparency chunk, tRNS [...]
In effect, it transforms the palette from an RGB lookup table to an RGBA table
[...] a single PNG transparency entry should come first"
{quote}
[http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
h4. general PDF encoding strategy
Option 1:
{quote}most libraries just undo the palettization and use a full color image +
mask.
{quote}
[https://forums.adobe.com/message/6148131#6148131]
Option 2:
{quote}SMask would be simpler since you could leave the palette in place
{quote}
[https://forums.adobe.com/message/6148557#6148557]
h4. what does FOP do
It creates a chroma-key mask:
{code:java}
/Type /XObject
/ColorSpace [/Indexed /DeviceRGB 255 ]
/Mask [182 182 151 151 158 158]
{code}
Acrobat Reader even fails to read those files while PDF viewers embedded into
Chrome/Firefox read the file, but show visual glitches.
FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to do
that:
[https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
In fact the following results in missing Option 2:
{code:java}
public void setup(PDFDocument doc) {
RenderedImage ri = getImage().getRenderedImage();
// code deleted
Raster raster = GraphicsUtil.getAlphaRaster(ri);
if (raster != null) {
AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
raster);
this.softMask = doc.addImage(null, alphaImage).makeReference();
}
{code}
[https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
In the above code raster will be null and therefore FOP fails to initialize a
softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
{{ColorModel.getAlphaRaster()}}, which returns null:
{quote}If this is an IndexColorModel which has alpha in the lookup table, this
method will return null since there is no spatially discrete alpha channel.
{quote}
[https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html]
This code will then add the chroma key mask to the image:
{code:java}
protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary dict,
IndexColorModel icm) {
// code deleted
Integer index = getIndexOfFirstTransparentColorInPalette(icm);
if (index != null) {
PDFArray mask = new PDFArray(dict);
mask.add(index);
mask.add(index);
dict.put("Mask", mask);
}
}
{code}
[https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java]
h4. why care to support?
Libraries such as pngquant optimize images for web usage and low footprint and
can not be used directly with Apache FOP as source images:
{quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8 bit
color palette with dithering. It will build indexed-color PNG's with alpha
transparency colors conveyed in the tRNS chunk."
{quote}
[https://imagemagick.org/Usage/formats/#png_non-im]
h4. sample data
{code}
$ identify -verbose sample_image_palette_tRNS.png
Format: PNG (Portable Network Graphics)
Type: PaletteAlpha
png:IHDR.color_type : 3 (Indexed)
png:tRNS : chunk was found
{code}
was:
h4. TL;NR
When using palette-based transparency via tRNS chunk in PNG images, the
generated PDFs are broken.
h4. palette-based with transparency.
{quote}*8.5.2. Palette-Based with Transparency*
"The PNG spec forbids the use of a full alpha channel with palette-based
images, but it does allow `cheap alpha` via the transparency chunk, tRNS [...]
In effect, it transforms the palette from an RGB lookup table to an RGBA table
[...] a single PNG transparency entry should come first"
{quote}
[http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
h4. general PDF encoding strategy
Option 1:
{quote}most libraries just undo the palettization and use a full color image +
mask.
{quote}
[https://forums.adobe.com/message/6148131#6148131]
Option 2:
{quote}SMask would be simpler since you could leave the palette in place
{quote}
[https://forums.adobe.com/message/6148557#6148557]
h4. what does FOP do
It creates a chroma-key mask:
{code:java}
/Type /XObject
/ColorSpace [/Indexed /DeviceRGB 255 ]
/Mask [182 182 151 151 158 158]
{code}
Acrobat Reader even fails to read those files while PDF viewers embedded into
Chrome/Firefox read the file, but show visual glitches.
FOP doesn't
[jira] [Updated] (FOP-2847) Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Tobias Hain updated FOP-2847:
-
Attachment: sample_image_palette_tRNS.png
> Support palette-based transparency via tRNS chunk of PNG images in PDF export
> -
>
> Key: FOP-2847
> URL: https://issues.apache.org/jira/browse/FOP-2847
> Project: FOP
> Issue Type: Bug
> Components: renderer/pdf
>Affects Versions: 2.3
>Reporter: Tobias Hain
>Priority: Major
> Attachments: sample_image_palette_tRNS.png
>
>
> h4. TL;NR
> When using palette-based transparency via tRNS chunk in PNG images, the
> generated PDFs are broken.
>
> h4. palette-based with transparency.
> {quote}*8.5.2. Palette-Based with Transparency*
> "The PNG spec forbids the use of a full alpha channel with palette-based
> images, but it does allow `cheap alpha` via the transparency chunk, tRNS
> [...] In effect, it transforms the palette from an RGB lookup table to an
> RGBA table [...] a single PNG transparency entry should come first"{quote}
> http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2
> h4. general PDF encoding strategy
> Option 1:
> {quote}most libraries just undo the palettization and use a full color image
> + mask.{quote}
> https://forums.adobe.com/message/6148131#6148131
> Option 2:
> {quote}SMask would be simpler since you could leave the palette in
> place{quote}
> https://forums.adobe.com/message/6148557#6148557
> h4. what does FOP do
> It creates a chroma-key mask:
>
> {code}
> /Type /XObject
> /ColorSpace [/Indexed /DeviceRGB 255 ]
> /Mask [182 182 151 151 158 158]
> {code}
> Acrobat Reader even fails to read those files while PDF viewers embedded into
> Chrome/Firefox read the file, but show visual glitches.
> FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to
> do that:
> https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG
> In fact the following results in missing Option 2:
> {code}
> public void setup(PDFDocument doc) {
> RenderedImage ri = getImage().getRenderedImage();
> // code deleted
> Raster raster = GraphicsUtil.getAlphaRaster(ri);
> if (raster != null) {
> AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
> raster);
> this.softMask = doc.addImage(null, alphaImage).makeReference();
> }
> {code}
> https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java
> In the above code raster will be null and therefore FOP fails to initialize a
> softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
> {{ColorModel.getAlphaRaster()}}, which returns null:
> {quote}If this is an IndexColorModel which has alpha in the lookup table,
> this method will return null since there is no spatially discrete alpha
> channel.{quote}
> https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html
> This code will then add the chroma key mask to the image:
> {code}
> protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary
> dict, IndexColorModel icm) {
> // code deleted
> Integer index = getIndexOfFirstTransparentColorInPalette(icm);
> if (index != null) {
> PDFArray mask = new PDFArray(dict);
> mask.add(index);
> mask.add(index);
> dict.put("Mask", mask);
> }
> }
> {code}
> https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java
> h4. why care to support?
> Libraries such as pngquant optimize images for web usage and low footprint
> and can not be used directly with Apache FOP as source images:
> {quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8
> bit color palette with dithering. It will build indexed-color PNG's with
> alpha transparency colors conveyed in the tRNS chunk."{quote}
> https://imagemagick.org/Usage/formats/#png_non-im
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[jira] [Updated] (FOP-2847) Support palette-based transparency via tRNS chunk of PNG images in PDF export
[
https://issues.apache.org/jira/browse/FOP-2847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Tobias Hain updated FOP-2847:
-
Description:
h4. TL;NR
When using palette-based transparency via tRNS chunk in PNG images, the
generated PDFs are broken.
h4. palette-based with transparency.
{quote}*8.5.2. Palette-Based with Transparency*
"The PNG spec forbids the use of a full alpha channel with palette-based
images, but it does allow `cheap alpha` via the transparency chunk, tRNS [...]
In effect, it transforms the palette from an RGB lookup table to an RGBA table
[...] a single PNG transparency entry should come first"
{quote}
[http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2]
h4. general PDF encoding strategy
Option 1:
{quote}most libraries just undo the palettization and use a full color image +
mask.
{quote}
[https://forums.adobe.com/message/6148131#6148131]
Option 2:
{quote}SMask would be simpler since you could leave the palette in place
{quote}
[https://forums.adobe.com/message/6148557#6148557]
h4. what does FOP do
It creates a chroma-key mask:
{code:java}
/Type /XObject
/ColorSpace [/Indexed /DeviceRGB 255 ]
/Mask [182 182 151 151 158 158]
{code}
Acrobat Reader even fails to read those files while PDF viewers embedded into
Chrome/Firefox read the file, but show visual glitches.
FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to do
that:
[https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG]
In fact the following results in missing Option 2:
{code:java}
public void setup(PDFDocument doc) {
RenderedImage ri = getImage().getRenderedImage();
// code deleted
Raster raster = GraphicsUtil.getAlphaRaster(ri);
if (raster != null) {
AlphaRasterImage alphaImage = new AlphaRasterImage("Mask:" + getKey(),
raster);
this.softMask = doc.addImage(null, alphaImage).makeReference();
}
{code}
[https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/ImageRenderedAdapter.java]
In the above code raster will be null and therefore FOP fails to initialize a
softMask. {{GraphicsUtil.getAlphaRaster()}} calls internally
{{ColorModel.getAlphaRaster()}}, which returns null:
{quote}If this is an IndexColorModel which has alpha in the lookup table, this
method will return null since there is no spatially discrete alpha channel.
{quote}
[https://docs.oracle.com/javase/8/docs/api/index.html?java/awt/image/ColorModel.html]
This code will then add the chroma key mask to the image:
{code:java}
protected void populateXObjectDictionaryForIndexColorModel(PDFDictionary dict,
IndexColorModel icm) {
// code deleted
Integer index = getIndexOfFirstTransparentColorInPalette(icm);
if (index != null) {
PDFArray mask = new PDFArray(dict);
mask.add(index);
mask.add(index);
dict.put("Mask", mask);
}
}
{code}
[https://github.com/apache/fop/blob/ff452f3685a02715aee791d651b58dd1797ddfd4/fop-core/src/main/java/org/apache/fop/render/pdf/AbstractImageAdapter.java]
h4. why care to support?
Libraries such as pngquant optimize images for web usage and low footprint and
can not be used directly with Apache FOP as source images:
{quote}"*pngquant*: Lossy PNG optimizer, reducing a PNG image down to an 8 bit
color palette with dithering. It will build indexed-color PNG's with alpha
transparency colors conveyed in the tRNS chunk."
{quote}
[https://imagemagick.org/Usage/formats/#png_non-im]
h4. sample data
{code}
!
{code}
was:
h4. TL;NR
When using palette-based transparency via tRNS chunk in PNG images, the
generated PDFs are broken.
h4. palette-based with transparency.
{quote}*8.5.2. Palette-Based with Transparency*
"The PNG spec forbids the use of a full alpha channel with palette-based
images, but it does allow `cheap alpha` via the transparency chunk, tRNS [...]
In effect, it transforms the palette from an RGB lookup table to an RGBA table
[...] a single PNG transparency entry should come first"{quote}
http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.5.2
h4. general PDF encoding strategy
Option 1:
{quote}most libraries just undo the palettization and use a full color image +
mask.{quote}
https://forums.adobe.com/message/6148131#6148131
Option 2:
{quote}SMask would be simpler since you could leave the palette in place{quote}
https://forums.adobe.com/message/6148557#6148557
h4. what does FOP do
It creates a chroma-key mask:
{code}
/Type /XObject
/ColorSpace [/Indexed /DeviceRGB 255 ]
/Mask [182 182 151 151 158 158]
{code}
Acrobat Reader even fails to read those files while PDF viewers embedded into
Chrome/Firefox read the file, but show visual glitches.
FOP doesn't implement Option 1 yet. None of the ImageLoaders is prepared to do
that:
https://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG
In fact the following results in missing Option 2:
{code}
public
