After a very, very long process of elimination, I discovered that a problem I'm having with image artifacting in a script I'm writing is related simply to style rules. I'm adjusting the opacity of an image with the properties "opacity" (for standards compliant) and "filter:alpha(opacity=x)" (for IE). Here's the IE-relevant code:
View the example at this link and you'll see what problem this is creating in IE: http://tarsus.freehostia.com/image_test.html
(For certain in IE6, but I believe it's happening in IE7 too.) I chose an image that gets particularly mangled, but this happens to some degree with any fairly dark image.
Don't know about how it was saved - just grabbed that one off the Internet. However, I can't rely on images being saved in a specific way (that is, if it can be helped!), because I'm designing this script to be very, very versatile. It's designed to allow a user to simply dump any number of images, any format, any size, into a directory, and the script will transform all images in that directory into an interactive slideshow.
I gave it a try, but I'm afraid I have little experience with using this style property and am not sure how you mean it to be incorporated. How do I also use the filter property to specify the opacity? This is what I tried:
No luck. As long as the alpha filter is on, the image gets ruined.
What's amazing to me is that this doesn't happen all the time for any developer using transparency on an image. The other images I'm working with aren't nearly as bad as this one, but there are noticeable scattered specks on many of them. These are images I grabbed from many different places on the web, just for testing purposes, so the problem can't be isolated to an issue with saving the images. No one has run into this before?