When digitizing paper books, I often scan the front and back pages at 300 dpi color setting and the text at 600 dpi black and white setting. To extract the original image file from such a PDF file with mixed color space (image type) and resolution, simply select "Determine Automatically" for color space and resolution in Acrobat and then save the images. Then the files will be output with the original color space and resolution of each page.
- File format options for PDF export in Acrobat
https://helpx.adobe.com/acrobat/using/file-format-options-pdf-export.html
It is difficult to know the color space and resolution of a file created by someone else, and even more so when dealing with a PDF file consisting of many pages. Even though Acrobat supports automatic determination of color space and resolution, it is only a simple case of one image per page. However, even with such automatic determination, there is a big difference with and without.
Thank you for taking the time to read this message.
Best regards,
rakunavi
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