Hi everyone, have a few questions about jpg artifacts...maybe someone can help me. What are they? Can they be created by just saving your bmp file as a jpg? Can you get rid of them once you have them? How can you tell that you have them? Sorry to sound so dense but I really have no experience with this. Thanks!

.jpg artifacts are created when you overcompress an image file when saving a Bitmap (bmp) image in a paint program using the JPeg format to decrease the file size. You will see the artifacts as blocky areas especially between the transition of two colors. Here is an extreme example.

Here is the same image with a more normal compression. The idea is to compress as much as possible without artifacts. Most paint programs with an option for saving in the .jpg format allow you to adjust the amount of compression before saving. As to getting rid of them, once you save the image with overcompression, you are stuck with them in that version. But you still have the original to try again. :^) Hope this helps. John

Attached Link: http://www.digitalriver.com/dr/v2/ec_MAIN.Entry10?V1=101359&PN=1&SP=10023&xid=8282&CID=0&DSP=&CUR=8

Aye, but I've never seen a paint program, not even Photoshop, which gives you full 8-bit control over your .jpg compression. I've been using a program called Riptide, by Vorton, for years. It will calculate a target file size for an image, or allow you to choose your compression on a 256-level (8-bit) scale, instead of 10 or 12 or lo and hi, like many programs. It also does batch-conversions, so you can rip a whole .bmp folder to .jpg and set compression and resizing, if necessary. Makes thumbnailing for Renderosity a snap!

photoshop does that too under save for web so does fireworks.

YSVRY, no they don't. Neither program can touch Riptide for .jpg conversion, alas... Also, Riptide will import any file type, and allow you to convert to any other type. Even PS can't do THAT!

I've never used Riptide so I can't say, but from what I've read it can't open PDF or raw postscript files, which photoshop can. Although it does open a host of file formats that PS doesn't, many of which I've never heard of. And I'm pretty sure ysvry is correct. In fact under the save for web you can select your target file size, and set the maximum and minimum quality settings and set the image size by pixels or percentage. I'm not quite sure what you mean by 256-level (8-bit) scale. Batch processing in Photoshop has been available for some time, you can check out this link, it has a tutorial on using Photoshop Actions: http://www.creativemac.com/2002/04_apr/tutorials/psbatch.htm

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I think I understand now. The images show a clear difference in the amount of blending of color hues and image sharpness...like there's more information in the normal compression image. Riptide looks interesting and I have PSP7 which has a "save to web" choice but I always thought that was poorer quality image. Maybe the best thing is for me to open a bmp file and try saving it at different compressions or give Riptide a whirl. Thanks for the links too!

Aye, Bandolin, I understand all of what you're saying. Photoshop CAN do all of those things! But Riptide does it better. Photoshop copmression leave more artifacts, and is not "lossless". And Photoshop still doesn't let you access the 8-bit spectrum for compression, I'm using PS 7 anyway. The "Save for Web" option is slow and useless if you have Riptide.

PhotoPaint has a 0 to 100 scale setting for compression, sub format selection, and a 0 to 100 scale for smoothing control. I also has a realtime preview and resulting file size display. Works a serious treat for jpg saves.