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https://issues.apache.org/jira/browse/PDFBOX-1870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13888103#comment-13888103
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John Hewson edited comment on PDFBOX-1870 at 1/31/14 8:15 PM:
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Ok, I've added a test file, the issue is that the 2nd image down was displaying
previously (the blue one) but now is blank. The blue image is the "correct" one
as far as trunk is concerned right now. The image is rendered using a CMYK tint
transform function.
I'm working on a major rewrite of color space and imaging code currently, so
don't worry about all the other problems this file has. I have fixes for all of
them.
EDIT: Also, rendering the file is very slow, I have performance fixes which I'm
working on also.
was (Author: jahewson):
Ok, I've added a test file, the issue is that the 2nd image down was displaying
previously (the blue one) but now is blank. The blue image is the "correct" one
as far as trunk is concerned right now. The image is rendered using a CMYK tint
transform function.
I'm working on a major rewrite of color space and imaging code currently, so
don't worry about all the other problems this file has. I have fixes for all of
them.
> PDFunctionType0 incorrect
> -------------------------
>
> Key: PDFBOX-1870
> URL: https://issues.apache.org/jira/browse/PDFBOX-1870
> Project: PDFBox
> Issue Type: Sub-task
> Components: PDModel
> Affects Versions: 2.0.0
> Reporter: Tilman Hausherr
> Priority: Minor
> Attachments: PDFunctionType0.patch, technical_v2_p9.before.jpg,
> technical_v2_p9.before.pdf, technical_v2_p91.after.jpg
>
>
> Type 0 (Sampled) Functions are described in 3.9.1 of the pdf spec and
> basically, its cheating: there's an n-dimensional grid of values ("samples")
> and the function shall return these values or something in-between.
> PDFunctionType0 has two bugs:
> 1) it does not do any interpolation. The function interpolate() is called
> several times, but only adjust values between ranges etc, not to calculate
> the color between 2^n samples - that part is "outputValues[i] =
> (outputValuesPrevious[i] + outputValuesNext[i]) / 2". The spec does not tell
> much, only that "Interpolation is used to determine output values from the
> nearest surrounding values in the sample table". I have done a
> linear/bilinear interpolation implementation for 1D/2D inputs. I did not do
> an interpolation implementation for 3D and higher, because its unclear
> whether this is actually used. Instead, I return random (!) values.
> 2) the sample bits are not collected correctly, the current code ignores the
> leftover bits when a row is done. The spec tells us "Successive values are
> adjacent in the bit stream; there is no padding at byte boundaries". Luckily,
> that one is easy to correct, three lines must be moved up. Alternatively, one
> might use the bit-io lib I mention in PDFBOX-615.
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