I have a PDF where each page is a full-colored image (it's an artbook). There are 16 pages. One page is completely blank.
The PDF itself is 140 MB. When I extract each image to BMP, the images only take up 30 MB. Lossless compression to PNG yielded 13 MB.
How is it possible that the PDF is 140 MB when the images themselves is (is arguably at worst) 30 MB? Are PDF's using an extremely inefficient way to store image data where each pixel takes up more than 4 bytes?
I like PDF because a lot of applications support it without having to install additional software/plugins, but this I found this quite strange.
I'm not sure if this particular PDF is just a special case.