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asdfgh2
PostPosted: Wed Jan 26, 2011 3:04 pm 
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Joined: Wed Jan 26, 2011 2:51 pm
Posts: 3
Hi there.

I tried the image export sample from
http://www.pdfsharp.net/wiki/ExportImages-sample.ashx
but it's not working with CMYK images.
The saved images look like negative RGB.

Code:
static void ExportJpegImage(PdfDictionary image, ref int count)
{
  // Fortunately JPEG has native support in PDF and exporting an image is just writing the stream to a file.
  byte[] stream = image.Stream.Value;
  FileStream fs = new FileStream(String.Format("Image{0}.jpeg", count++), FileMode.Create, FileAccess.Write);
  BinaryWriter bw = new BinaryWriter(fs);
  bw.Write(stream);
  bw.Close();
}


best regards!

Edit: ColorSpace Key of the PDFDictionary.Element Property is "34 0 R"
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Thomas Hoevel
PostPosted: Wed Jan 26, 2011 4:19 pm 
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Posts: 3101
Location: Cologne, Germany
asdfgh2 wrote:
Edit: ColorSpace Key of the PDFDictionary.Element Property is "34 0 R"

This is a reference to element 34 in your PDF file.

Acrobat can display negated images (check the "/DECODE" entry of the PDF file).

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Thomas Hoevel
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asdfgh2
PostPosted: Fri Jan 28, 2011 7:09 pm 
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Joined: Wed Jan 26, 2011 2:51 pm
Posts: 3
Thanks for your answer!
how can i access element 34 then? theres no entry in page.elements.
however i am not sure if you understood my question probably:
i want to save images from a pdf as JPG i dont want to save a pdf.

best regards!
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Thomas Hoevel
PostPosted: Mon Jan 31, 2011 9:19 am 
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Location: Cologne, Germany
asdfgh2 wrote:
however i am not sure if you understood my question probably:
i want to save images from a pdf as JPG i dont want to save a pdf.

That's what I understood.
But the reference to object 34 doesn't help those who don't have that PDF file.

When you open the file with PDFsharp, PDFsharp will handle the references for you.

The PDF file contains the JPEG image - and it contains the filter parameters that instruct Adobe Reader how to display the image. Filter parameters can specify that 1 is white and 0 is black - or that 1 is black and 0 is white.

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asdfgh2
PostPosted: Mon Jan 31, 2011 1:14 pm 
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Joined: Wed Jan 26, 2011 2:51 pm
Posts: 3
ok now i understand :)
So i have to decode the image before saving.
thank you very much!
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mbeditions
PostPosted: Fri Apr 22, 2011 8:54 am 
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Joined: Fri Apr 22, 2011 8:50 am
Posts: 1
Hi,

I've exactly the same problem. Can you post your solution please ?

Thanks.
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