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https://issues.apache.org/jira/browse/PDFBOX-4598?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16887814#comment-16887814
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Jörg Henne commented on PDFBOX-4598:
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Yes, indeed, the code in question is about generating grayscale from bi-level
data during resampling. If we generate bi-level output using nearest-neighbor
subsampling (or even something a little smarter) we may lose important detail,
especially fine lines as in CAD drawings. Some of the samples used during the
original Implementation of the code are high-resolution scans of A1 and A0
drawings of municipal waterworks. When downsampling to one bit you lose most of
the lines and thus all legibility. Also, see the comment here:
[https://github.com/apache/pdfbox-jbig2/blob/3.0.2/src/main/java/org/apache/pdfbox/jbig2/image/Bitmaps.java#L110]
However, I understand your issue with the 8-fold expansion of the size for
unscaled cases. Maybe you could modify your patch so that 1 bpp is returned for
the unscaled case only? Another approach would be to determine whether we know
the physical target resolution and try to apply souce subsampling using
{{setSourceRenderSize}} as suggested by Tilman?
> oversized jbig2 decoded result that causing unnecessary operation
> -----------------------------------------------------------------
>
> Key: PDFBOX-4598
> URL: https://issues.apache.org/jira/browse/PDFBOX-4598
> Project: PDFBox
> Issue Type: Bug
> Components: JBIG2
> Affects Versions: 3.0.2 JBIG2
> Reporter: Hee Jeong Kim
> Priority: Minor
> Attachments: sample.pdf, use_packed_raster_to_read_Jbig2_image.patch
>
>
> Hi! I am using pdfbox 2.0.16 and jbig2-imageio 3.0.2 to read JBIG2 images,
> and found some issue to report.
> It seems like jbig2-imageio creates oversized BufferedImage, and this also
> makes pdfbox to do unnecessary operations.
> To read Jbig2 image, pdfbox with jbig2-imageio do followings:
> 1. find JBIG2 ImageReader
> (https://github.com/apache/pdfbox/blob/2.0.16/pdfbox/src/main/java/org/apache/pdfbox/filter/JBIG2Filter.java#L67)
> 2. read Image and get BufferedImage as a result
> (https://github.com/apache/pdfbox/blob/2.0.16/pdfbox/src/main/java/org/apache/pdfbox/filter/JBIG2Filter.java#L106)
> 2-1. JBIG2 ImageIO 3.0.2 get decoded bitmap
> (https://github.com/apache/pdfbox-jbig2/blob/3.0.2/src/main/java/org/apache/pdfbox/jbig2/JBIG2ImageReader.java#L249)
> 2-2. return the given bitmap as buffered image
> (https://github.com/apache/pdfbox-jbig2/blob/3.0.2/src/main/java/org/apache/pdfbox/jbig2/JBIG2ImageReader.java#L259)
> The problem is
> At step 2-1, roughly 59MB Bitmap is created for given Jbig2 image on the
> second page of sample.pdf (which is correct),
> but oversize(473MB, roughly) BufferedImage is returned at the step 2-2.
> I think this is because jbig2-imageio uses a raster based on a
> PixelInterleavedSampleModel and IndexColorModel with 8 bits.
> https://github.com/apache/pdfbox-jbig2/blob/3.0.2/src/main/java/org/apache/pdfbox/jbig2/image/Bitmaps.java#L177
> https://github.com/apache/pdfbox-jbig2/blob/3.0.2/src/main/java/org/apache/pdfbox/jbig2/image/Bitmaps.java#L286
> https://github.com/apache/pdfbox-jbig2/blob/3.0.2/src/main/java/org/apache/pdfbox/jbig2/image/Bitmaps.java#L291
> This also makes pdfbox to check a pixel size of the color model of result
> buffered image,
> https://github.com/apache/pdfbox/blob/2.0.16/pdfbox/src/main/java/org/apache/pdfbox/filter/JBIG2Filter.java#L116
> and to create another BufferedImage with binary type since it is not 1.
> (jbig2 is 1-bit depth)
> https://github.com/apache/pdfbox/blob/2.0.16/pdfbox/src/main/java/org/apache/pdfbox/filter/JBIG2Filter.java#L122
> I think we should call createPackedRaster and use the returned raster which
> is based on MultiPixelPackedSampleModel, and use IndexColorModel with 1 bits
> since jbig2 is for bi-level image. Please check the attached patch. I tested
> with the patch, and it seems like this patch works well.
> You can reproduce this issue with the second of the sample.pdf file that I
> attached.
> You can also download the file from here:
> http://www.newsgn.com/data/newsgn_com/pdf/201802/2018022229524590.pdf
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