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BW Dithered image renders to Gray Scale |
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John Sigoloff 
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Joined: 20 Sep 06 Status: Offline Points: 11 |
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 Topic: BW Dithered image renders to Gray ScalePosted: 30 Dec 07 at 3:44PM |
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I have a black and white PDF that is rendered by QP to a gray scale image. I have checked it with GhostScript and Adobe and it is a black and white. The image was color and was converted to BW dithered (ie different BW patterns for different shades of gray). Any help would be appreciated
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marian_pascalau
Debenu Quick PDF Library Expert 
Joined: 28 Mar 06 Location: Germany Status: Offline Points: 278 |
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Posted: 03 Jan 08 at 7:50AM |
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Send sample to support(at)quickpdf(dot)org
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Ingo
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Joined: 29 Oct 05 Status: Offline Points: 3524 |
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Posted: 03 Jan 08 at 8:15AM |
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Hi John!
Perhaps it's better to upload a sample online and post the link (with an error description) here - so anybody who's reading here can help and not only one ;-) Best regards and a happy new year, Ingo |
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John Sigoloff
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Joined: 20 Sep 06 Status: Offline Points: 11 |
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Posted: 03 Jan 08 at 11:17PM |
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See next post
Edited by John Sigoloff - 03 Jan 08 at 11:19PM |
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John Sigoloff
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Posted: 03 Jan 08 at 11:18PM |
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See image: http://home.netcom.com/~jsiggy/BW_Renders_Gray.pdf for an example of a BW Dithered image that renders gray & dithered...
Regards,
John
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Ingo
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Joined: 29 Oct 05 Status: Offline Points: 3524 |
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Posted: 04 Jan 08 at 2:48AM |
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Hi John!
Inside you can find this: /ColorSpace /DeviceGray /BitsPerComponent 1 If tested with QP 5.21 ... It's gray scaled, with Sumatra 0.6, Foxit Reader 2.2 and Adobe Reader 8.1 ... It looks always bw dithered. Perhaps the reason is only the size of your qp-rendered image and it only seems to be gray scaled? If i reduce the zoom of the above readers the document seems to be gray scaled, too...? Best regards, Ingo |
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lcarrere
Debenu Quick PDF Library Expert
Joined: 10 Jul 06 Location: France Status: Offline Points: 47 |
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Posted: 04 Jan 08 at 4:09AM |
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Hi all and happy new year.
Ingo, As you know, IsedQuickPDF uses the GDI+ functions to draw images & shapes during the rendering process. I haven't the source code of the library but I think the "problem" come from here: When the bw image is drawn into a gdi+ graphics, the interpolation mode used are not InterpolationModeNearestNeighbor. In this case, with 1bpp rendering process the resulting drawn image appears as grayscale. With GDI+ when we draw image into graphic kepping original size the best way is to set the Interpolation mode to InterpolationModeNearestNeighbor and the smoothing mode to SmoothingModeNone (see gdi+ reference guide). Best regards, Loïc Carrère Edited by lcarrere - 04 Jan 08 at 4:17AM |
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John Sigoloff
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Posted: 04 Jan 08 at 4:17PM |
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Loic et al,
setting the Interpolation mode to InterpolationModeNearestNeighbor (source required) and the smoothing mode to SmoothingModeNone solved the problem. Thanks alot...
Cheers,
John
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