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#1 Posted : Tuesday, July 28, 2009 7:22:06 AM(UTC)

Kiima  
Kiima

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Hey there! Is there a way to see if a PDF is black and white? I've tried checking the BPP, but CodecsImageInfo returns 24 even if the image is black and white. Please advise.

Thanks,
Kiima
LeadTools 16.5, Windows VB.NET

 

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#2 Posted : Wednesday, July 29, 2009 5:51:24 AM(UTC)

Adam Boulad  
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Kiima,
You could do this by:
1. Loading the PDF file as 24-bit.
2. Count the unique colors in the file using the ColorCountCommand Class function:
- If the number of colors is more than two, the image will not be black and white.
3- If the number of colors is 2 or less, perform ColorResolutionCommand Class with the
ColorResolutionCommandPaletteFlags.Optimized flag.
4- Check entries of the palette to see if they are black and white entries.

 
#3 Posted : Wednesday, July 29, 2009 6:15:16 AM(UTC)

Kiima  
Kiima

Groups: Registered
Posts: 25


Thanks for the response....I'll test it out today.

On a related note, which PDF compression format would you recommend for the black and white images? I've tried the RasPdfG4 format, but the images look pixely. We use the RasPdfJpeg411 format for color pdfs.

Thanks,
  -Kiima
LeadTools 16.5, Windows VB.NET
 
#4 Posted : Thursday, July 30, 2009 4:57:28 AM(UTC)

Adam Boulad  
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CCITT Group4 usually gives very good compression, especially with document-like images.
JBIG and JBIG 2 can give higher compression, but they're only available in LEADTOOLS Document Imaging and above. For more information, please check the product comparison chart at our website.
The issue could be related to the bitmap's resolution. What is the source image? Is it also PDF? If yes, are you setting its loading DPI to a high value?

 
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