Extracting Embedded Images from a PDF

Surprisingly, the best way (that I’ve found) to do this is to use The Unarchiver, a free app from MacPaw (the folks behind SetApp and many other things). It seems to faithfully extract the images as-is, including ICC profiles (which might technically be separate from the image within the PDF, but nonetheless are crucial to the image being extracted correctly).

The primary reason to extract the images exactly as is, bit-for-bit-identical, is that they’re typically already lossy-compressed (usually JPEG). Recompressing them will introduce further losses or increase the file size1, or both.

Kudos to Josef Habr for suggesting The Unarchiver on StackExchange – I would never have found it on my own, even though I already had it installed and use it occasionally (for more traditional archive file formats, like Zip or StuffIt).

Frustratingly, Josef’s post aside, none of the recommendations you read online mention The Unarchiver, pointing instead to other options which are harder to install, harder to use, and don’t extract the images correctly. Worst of all, many people falsely claim that their suggested approach will extract the images losslessly. Examples include:

• pdfimages from Poppler – silently re-encodes images in some cases (contrary to what its documentation and users claim), such as if they have non-sRGB colour profiles, and fails to preserve the embedded ICC profile. Worse, the developers have known about this for nearly a decade and refuse to fix it.
• pdftoppm (et al) – explicitly convert the embedded images into another format, which while usually a lossless format (e.g. PNG or PPM) by default, still requires you to then re-encode them for use online etc. Plus, they typically don’t preserve ICC profiles.
• ImageMagick – doesn’t extract the images, merely renders the whole PDF page(s) as images, requiring further post-processing and inevitably reducing the image quality (due to mismatched output resolution and pixel alignment vs the embedded images’).
• Exporting…