Tilman Hausherr created PDFBOX-3768:
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Summary: Optimize SampledImageReader.from1Bit()
Key: PDFBOX-3768
URL: https://issues.apache.org/jira/browse/PDFBOX-3768
Project: PDFBox
Issue Type: Improvement
Components: Rendering
Affects Versions: 2.0.5
Reporter: Tilman Hausherr
Assignee: Tilman Hausherr
Fix For: 2.0.6, 3.0.0
The from1bit() path passes a raster to {{colorSpace.toRGBImage(raster)}} where
an RGB BufferedImage is created, which means a big memory footprint for scanned
images.
I tried optimizing by using the raster to create smaller BufferedImages.
Instead of calling {{colorSpace.toRGBImage(raster)}} where the raster would be
copied into an RGB image, I did this:
{code}
byte[] indexedValues = new byte[] { 0, (byte)0xFF };
ColorModel colorModel = new IndexColorModel(1, 2, indexedValues, indexedValues,
indexedValues);
return new BufferedImage(colorModel, raster, false, null);
{code}
Sadly, this resulted in a bigger memory footprint.
Lowest possible -Xmx setting to convert a file with 300dpi A4 scans: 76m
With the optimization: 123m
The stack trace suggests that java copies the image to an RGB image:
{code}
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
at java.awt.image.DataBufferInt.<init>(Unknown Source)
at java.awt.image.Raster.createPackedRaster(Unknown Source)
at java.awt.image.DirectColorModel.createCompatibleWritableRaster(Unknown
Source)
at java.awt.image.BufferedImage.<init>(Unknown Source)
at sun.java2d.loops.GraphicsPrimitive.convertFrom(Unknown Source)
at sun.java2d.loops.GraphicsPrimitive.convertFrom(Unknown Source)
at sun.java2d.loops.MaskBlit$General.MaskBlit(Unknown Source)
at sun.java2d.loops.Blit$GeneralMaskBlit.Blit(Unknown Source)
at sun.java2d.pipe.DrawImage.blitSurfaceData(Unknown Source)
at sun.java2d.pipe.DrawImage.renderImageCopy(Unknown Source)
at sun.java2d.pipe.DrawImage.copyImage(Unknown Source)
at sun.java2d.pipe.DrawImage.copyImage(Unknown Source)
at sun.java2d.pipe.ValidatePipe.copyImage(Unknown Source)
at sun.java2d.SunGraphics2D.copyImage(Unknown Source)
at sun.java2d.pipe.DrawImage.makeBufferedImage(Unknown Source)
at sun.java2d.pipe.DrawImage.renderImageXform(Unknown Source)
at sun.java2d.pipe.DrawImage.transformImage(Unknown Source)
at sun.java2d.pipe.DrawImage.transformImage(Unknown Source)
at sun.java2d.pipe.DrawImage.transformImage(Unknown Source)
at sun.java2d.pipe.ValidatePipe.transformImage(Unknown Source)
at sun.java2d.SunGraphics2D.drawImage(Unknown Source)
at
org.apache.pdfbox.rendering.PageDrawer.drawBufferedImage(PageDrawer.java:1007)
{code}
After I mentioned this on the dev mailing list, [~pslabycz] replied:
{quote}
your message caught my attention, so I could not resist to try and investigate
it a little. I did not get too far and do not have the time to do any tests,
but maybe at least a small hint. To at least have a chance that the sun java2d
machinery draws the image without converting it first, BufferedImage.getType()
must return something else than TYPE_CUSTOM. (At least I think so) For
IndexColorModel, the raster has to be either BytePackedRaster or
ByteComponentRaster. ByteComponentRaster resulting in BufferedImage type
TYPE_BYTE_INDEXED is a safer bet.
{quote}
So I looked at the source of BufferedImage and everything created by a user is
TYPE_CUSTOM. Thus I tried using a TYPE_BYTE_BINARY image, but I got the same
OOM stack trace suggesting a copying is taking place. I tried getting drawImage
in the debugger but couldn't. But a look at the source code
http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b27/sun/java2d/pipe/DrawImage.java
shows at line 381 that java wants a "helper" and if there isn't, then it will
convert to RGB / ARGB. And that is what's done according to the stack trace.
What I didn't search in the source code is what "helpers" would be available.
Then, in an act of desperation, I tried TYPE_BYTE_GRAY. This worked! It uses 1
byte per pixel, thus saves 2/3 of the RGB footprint, and the intermediate
raster.
Minimal -Xmx setting got down to -Xmx26m.
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