Please note that while there is an existing question titled "How do I get the exact dimension of a picture in LaTeX?", that question is actually asking something different.
I have a document that contains several high-resolution png images, included as usual with commands like
within figure environments. However, my publisher is asking me for a version where each image is at "no more than 300 dpi, scaled at 100%".
This means, I think, that I have to manually resize all my images. I would like the document to look the same afterwards, so to do that I need to know exactly how much LaTeX is scaling them, or equivalently, the exact dimensions of the image as it appears in my document. That is, I need to know the numerical value of
0.85\columnwidth in inches, and if possible the height of the image in inches as well.
How can I find this out? I tried
\showthe\columnwidth, but this gives the following extremely informative error message:
Is it possible to print the exact dimensions of an image, or the scaling ratio used, to the console?