That's a new one on me. What are you using the images for, though? If they're destined for the web, dpi won't matter, as that's primarily an issue for printing. The actual pixel dimensions are what you need to worry about for web graphics.
Images are for desktop application resources.
And when I explain to PS users it's because of FW, it makes FW look sloppy.
If my calculations are correct, any image being drawn at 71.98DPI when it should have been drawn at 72 DPI will be off by at least 1 pixel for any image greater than 50px in dimension.
I can tell you that the DPI is payed attention to by OS X, because I was outputting at 71.2 DPI previously by mistake, and some images were exhibiting problems in the app. Max OS X supports image resolution independence to some degree.
I've logged a bug, but would love a workaround.
I'm having the exact same problem. Whenever I save an imagee in fireworks that's supposed to be saved at 72 DPI for some reason the final file output is saved at 71.98 DPI. Anyone know how to fix this>
I like Jim's answer on this—i.e., a pixel is a pixel. If an application is attempting to render the image based on ppi (or dpi) information, then it's really performing a sort of previewing, or sizing simulation. And I'd look to see if that feature can be turned off.
Mac's Preview application has long offered this option, under various names, and it can be turned on or off within Preferences. Here's how that preference appears in OS 10.6. It's the bottom option, "Size on screen equals size on printout", that accounts for pixel density in its image rendering. For example, an image set to 72 ppi will suddenly increase in size (on a typical screen) when this option is chosen.
Speaking of Preview, it includes an option to adjust Resolution under the Tools > Adjust Size command. (I believe you'd want to deselect "Resample Image" before making any adjustments in this dialog.) If Fireworks is letting you down, perhaps this option could help you out in a pinch.
It might be helpful here to know what application is providing you with the specific dpi information and/or what application is "receiving" these graphics. If the saved graphic is reopened in Fireworks, does Fireworks still indicate 72dpi? Is it simply rounding up? Does dpi fluctuate slightly between graphics of different pixel dimensions?
Finally, if the metric system is somehow an issue here, have you tried using metric sizing instead? (Following is the Modify > Canvas > Image Size... dialog within Fireworks 8, with 72ppi being converted to 28.346 pixels/cm.)