Use this function to acquire bitmap pictures stored within PDF files. The function stores JPEG-compressed pictures as JPEG files, and other pictures as PNG files.
This function only examines the part of the PDF that is needed in order to extract the pictures. Since that means that only the PDF file's picture data storage area is check, this function can acquire pictures even from a damaged, otherwise unusable PDF file (e.g. one badly downloaded from the Web). Because this method is used, the pictures are extracted exactly as they are stored in the PDF, and so they can have e.g. a different rotation than the one seen when viewing the PDF. For pictures with JPEG compression and CMYK color, you may want to use the Convert CMYK JPEG files to RGB option, since PDF stores pictures with CMYK color in a way that is incompatible with most programs. (Color information is stored in them in reverse.)
The PDF format can widely vary. Thus, this function has certain restrictions.
It only supports pictures within the following limits:
- colors: palette colors with 2, 4, 6, or 8 bits/pixel, or RGB or CMYK color.
- compression: only ASCII85, LZW, ZIP, JPEG, and JPEG2000.
This function does not support:
- acquiring pictures from files with copy-protected content
- acquiring pictures less than 5 pixels wide or high