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copied!<p>I do not know the library you use to access the inner structures of a PDF file but the problem at hand will have tree distinct subproblems:</p> <ol> <li>Find all images in the PDF file</li> <li>Decode the images to their components</li> <li>Convert the decoded image to a DIB</li> </ol> <p><em>Find all Images</em></p> <p>Images can occur inside content streams or in streams attached to dictionaries. To find all images in content streams, you need to find all content streams in either Pages, XObjects or Patterns. Each of those can have a Resources -> XObject dictionary that references all XObjects (and an XObject can be an Image). </p> <p>If you avoid the inline images you might simply scan the PDF file and each dectionary that is of type XObject subtype Image can be decoded.</p> <p><em>Decode</em></p> <p>All streams (inline in content streams) of in separate objects in the PDF file are encoded and mught need post processing using the Decode arrays. There are several filters that you need to be able to perform for decoding. Flate decode (ZLIB), JPEG and CCITT (fax G3/G4) are probable the most used for images. Hopefully the PDF library you use will know how to decode the streams..</p> <p>Next there are Decode arrays (a bit rare) where each color component can be scaled from an input value to an output value. This is a linear transformation.</p> <p><em>To DIB</em></p> <p>Next in line is the conversion of the decoded image to a DIB. This means you need to convert the color components to something Windows can 'get' (eg, Palette, grayscale (special palette) of RGB. PDF supports a very very large variety of color spaces and converting them to RGB is no sinecure. You best hope here is that the PDFs you need to process only use a select subset (like RGB and palette). Now a DIB can be simply created by creating the bitmap header (BITMAPINFO), fill in all data and call the DIB creation function CreateDIBSection and them process the DIB the way you application needs.</p> <p><em>Epilogue</em></p> <p>All in all: to be able to process all PDF files and find all images is quite a daunting task, if you control the source if teh PDFs and you know they are always in DeviceRGB format and always JPEG etc and never inlined into the content stream it is do-able.</p>

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