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https://issues.apache.org/jira/browse/PDFBOX-4184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16528728#comment-16528728
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Tilman Hausherr edited comment on PDFBOX-4184 at 6/30/18 2:05 PM:
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There's a new problem and I don't know why this didn't come up before. See this
code:
{code:java}
public void testCreateLosslessFrom16BitPNG() throws IOException
{
PDDocument document = new PDDocument();
BufferedImage image =
ImageIO.read(this.getClass().getResourceAsStream("16bit.png"));
assertEquals(64, image.getColorModel().getPixelSize());
assertEquals(Transparency.TRANSLUCENT,
image.getColorModel().getTransparency());
assertEquals(4, image.getRaster().getNumDataElements());
assertEquals(java.awt.image.DataBuffer.TYPE_USHORT,
image.getRaster().getDataBuffer().getDataType());
PDImageXObject ximage = LosslessFactory.createFromImage(document,
image);
int w = image.getWidth();
int h = image.getHeight();
validate(ximage, 16, w, h, "png", PDDeviceRGB.INSTANCE.getName());
System.out.println(ximage.getImage());
checkIdent(image, ximage.getImage());
checkIdentRGB(image, ximage.getOpaqueImage());
assertNotNull(ximage.getSoftMask());
validate(ximage.getSoftMask(), 8, w, h, "png",
PDDeviceGray.INSTANCE.getName());
assertEquals(35, colorCount(ximage.getSoftMask().getImage()));
doWritePDF(document, ximage, testResultsDir, "png16bit.pdf");
}
{code}
The test fails because the softmask is all 0. For some reason,
{{alphaImageData}} is not filled when {{prepareImageXObject}} is called by
{{preparePredictorPDImage}}. Could it be that when the PredictorEncoder path is
taken, that you forgot to handle the transparency?
was (Author: tilman):
There's a new problem and I don't know why this didn't come up before. See this
code:
{code:java}
public void testCreateLosslessFrom16BitPNG() throws IOException
{
PDDocument document = new PDDocument();
BufferedImage image =
ImageIO.read(this.getClass().getResourceAsStream("16bit.png"));
assertEquals(64, image.getColorModel().getPixelSize());
assertEquals(Transparency.TRANSLUCENT,
image.getColorModel().getTransparency());
assertEquals(4, image.getRaster().getNumDataElements());
assertEquals(java.awt.image.DataBuffer.TYPE_USHORT,
image.getRaster().getDataBuffer().getDataType());
PDImageXObject ximage = LosslessFactory.createFromImage(document,
image);
int w = image.getWidth();
int h = image.getHeight();
validate(ximage, 16, w, h, "png", PDDeviceRGB.INSTANCE.getName());
System.out.println(ximage.getImage());
checkIdent(image, ximage.getImage());
checkIdentRGB(image, ximage.getOpaqueImage());
assertNotNull(ximage.getSoftMask());
validate(ximage.getSoftMask(), 8, w, h, "png",
PDDeviceGray.INSTANCE.getName());
assertEquals(35, colorCount(ximage.getSoftMask().getImage()));
doWritePDF(document, ximage, testResultsDir, "png16bit.pdf");
}
{code}
The test fails because the softmask is all 0. For some reason,
{{alphaImageData}} is not filled when {{prepareImageXObject}} is called by
{{preparePredictorPDImage}}.
> [PATCH]: Support simple lossless compression of 16 bit RGB images
> -----------------------------------------------------------------
>
> Key: PDFBOX-4184
> URL: https://issues.apache.org/jira/browse/PDFBOX-4184
> Project: PDFBox
> Issue Type: Improvement
> Components: Writing
> Affects Versions: 2.0.9
> Reporter: Emmeran Seehuber
> Priority: Minor
> Fix For: 2.0.12, 3.0.0 PDFBox
>
> Attachments: 16bit.png, LoadGovdocs.java,
> lossless_predictor_based_imageencoding.patch,
> lossless_predictor_based_imageencoding_v2.patch,
> lossless_predictor_based_imageencoding_v3.patch,
> lossless_predictor_based_imageencoding_v4.patch,
> lossless_predictor_based_imageencoding_v5.patch,
> pdfbox_support_16bit_image_write.patch, png16-arrow-bad-no-smask.pdf,
> png16-arrow-bad.pdf, png16-arrow-good-no-mask.pdf, png16-arrow-good.pdf
>
>
> The attached patch add support to write 16 bit per component images
> correctly. I've integrated a test for this here:
> [https://github.com/rototor/pdfbox-graphics2d/commit/8bf089cb74945bd4f0f15054754f51dd5b361fe9]
> It only supports 16-Bit TYPE_CUSTOM with DataType == USHORT images - but this
> is what you usually get when you read a 16 bit PNG file.
> This would also fix [https://github.com/danfickle/openhtmltopdf/issues/173].
> The patch is against 2.0.9, but should apply to 3.0.0 too.
> There is still some room for improvements when writing lossless images, as
> the images are currently not efficiently encoded. I.e. you could use PNG
> encodings to get a better compression. (By adding a COSName.DECODE_PARMS with
> a COSName.PREDICTOR == 15 and encoding the images as PNG). But this is
> something for a later patch. It would also need another API, as there is a
> tradeoff speed vs compression ratio.
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