I was noticing that a GIF was being displayed with padding in FireFox 5 and IE 8. When I viewed the image size via FireBug, I noticed that it was a few pixels larger than expected.
Expected height: 160px vs. actual height: 171px
When I opened the GIF in an image editor, the editor displayed the correct dimensions, however when I ran ImageMagick identify I received the following information:
newGif.gif GIF 200x160 200x171+0+5 PseudoClass 256c 30kb
If I modified the geometry to 200x160+0+0 the image displayed as I expected it to in FireFox. FireFox and IE 8 seemed to be referencing the Image's page geometry rather than dimensions! Is my analysis correct and if so is this true for all image types or just GIF's?
Updated, I have included an image for your viewing pleasure! This image displays as 200 x 171 for me in FF, but is actually 200 x 160 when you download and view in a graphics program.
