Re: Fix for Bug 686980, stripes in pdf.

A possible resolution is to call the patch utility from GS makefiles.

Igor.

----- Original Message ----- 
From: "Jeong Kim" <[email protected]>
To: "'gs-code-review'" <[email protected]>
Sent: Tuesday, August 12, 2003 4:11 PM
Subject: [gs-code-review] Fix for Bug 686980, stripes in pdf.


> Reviewers,
> 
> In the given sample file, some parts of the pictures are using DCTDecode
> filter 
> with DeviceCMYK color space, but component id values in the stream data
> are not unique for each color channels. Again, they use same id values
> (1) for both cyan and black channel.
> 
> This makes a serious conflict and then jpeg decoder over-writes data for
> black 
> channel onto cyan channel for this reason. Therefore, output cyan
> channel has 
> data for black and black channel has dummy data.
> 
> That's why we have noisy black output and cyan images instead of black
> ones.
> 
> These problems are due to incorrect input data not to Ghostscript or
> jpeg library. But Adobe Acrobat reads this file corretly. So I did a
> clumsy hack on jpeg library.
> 
> In jpeg/jdmarker.c
> 
> 282:    INPUT_BYTE(cinfo, compptr->component_id, return FALSE);
> compptr->component_id = ci+1; <---
> 
> 327:    INPUT_BYTE(cinfo, cc, return FALSE);
>     cc = i+1; <---
> 
> I inserted two arrow-marked lines. Now jpeg library ignores the
> component id values from input stream. It just generates ids
> sequentially.
> 
> Now everything is OK. But I think modifying jpeg library instead of
> Ghostscript could be problematic. Any advice or comment on this issue is
> welcome.
> 
> Jeong
> 
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