How to prevent the Android Market from JPEG-compressing the Promotional Graphic PNG?
Use small images in kilobytes e.g. <5KB will do the job.
Uploaded promo image has to be quite small or Market will "process" it automatically (reduce its size). I had the same problem with >8KB images and at the end all went right with 3KB PNG/5KB JPEG files. Try using less colors, less effects, reduce quality, try with dithering also. At the end you will always make better quality image than Market will after processing (size reducing).
You can test/check this by yourself: - login to Android Market - upload promo image for your APK - open uploaded image in new window/tab and save it locally to your harddisk - check image size! it is a lot smaller than original ~15KB. Mine was ~3KB and original was ~17KB
Try these ones I made in photoshop. They're not perfect, but the size is much smaller so it may get a better treatment in the market:
saved for web, 100%, ICC profile, 0.2 blur:
saved for web, 100%, ICC profile, no blur:
Try these, I've made them in Adobe Fireworks, used simple Save As, with 2 different JPEG compression options (80% and 90%). Let us know, I would like to know the answer myself ;-)
JPEG 80% http://cl.ly/0m2c412p212n1r1w101u
JPEG 90% http://cl.ly/0627030I1U0P1R173W33
Sorry I can't insert pics yet as new user.