Find JPEG resolution with PHP

Question

Calling all PHP gurus!

I understand that you can use getimagesize() to get the actual pixel height and width of an image in PHP. However, if you open an image in pho

Answer 1

I don't understand this. Pixels = printsize x resolution, and the number of pixels is a set value. So, if you have an image of 300x300 pixels, you have 1"x1" of 300 DPI resolution, 2"x2" of 150 DPI resolution, or 4"x4" of 75 DPI resolution etc. An image doesn't have a resolution unless it has a physical size to compare to its pixel size.

What is it I'm missing? (and just how glaringly obvious is it to everyone else? =] )