== Format ==
* Drawings, icons, political maps, flags and other such images (basically those with large, simple, and continuous blocks of color) should be in [[PNG]] format.
* Photos and photo-like maps should be in [[JPEG]] format.
* Animations should be in animated [[GIF]] format.
In general, if you have a good image that is in the wrong format, convert it to the correct format before uploading. However, if you find a map, flag, etc in JPEG format, only convert it to PNG if this reduces the file size without causing artifacts. For further advice on converting JPEG to PNG, see [[Wikipedia:How to reduce colors for saving a JPEG as PNG]].
Most of the maps on the [[CIA World Factbook]] website were coded as JPEG, but are now coded as GIF. To update these photos, download the GIF picture from the CIA factbook, recode it in PNG format, and upload it to wikipedia.
Try to avoid cropping or otherwise editing JPEGs too frequently--each edit creates more loss of quality. If you can find an original of a photograph in 16-bit or 24-bit PNG or TIFF, edit that, and save as JPEG before you upload.
Avoid images that mix photographic and iconic content.
Though [[Cascading Style Sheets|CSS]] makes it easy to use a PNG overlay on top of a JPEG image, the Wikipedia software does not allow such a technique. Thus, both parts must be in the same file, and either the quality of one part will suffer, or the file size will be unnecessarily large.
See also: [[Wikipedia:How to keep image file sizes as small as possible]]