Gamification Wiki:Image guidelines/JPEG
JPEG, Joint Photographic Experts Group, usually designates an image file format (.JPEG or .JPG) that uses lossy compression, designed specifically for photography. It achieves a significant reduction in file size by encoding image data as a series of interfering frequencies, stored with varying degrees of precision, eliminating information that is less visually relevant. At high compression levels, image quality can decrease significantly.
- When uploading JPEG images to Gamification Wiki, make sure they are properly compressed. Compression estimates of 80%-85% generally produce small enough files without distorting too much. In any event, you should never need to go above 90%; the files simply become too big without any real increase in visual quality.
Note that even at maximum quality JPEG files are not guaranteed to be lossless. A "lossless JPEG" format specification does exist but is not supported by any mainstream applications.
One distinct lacking feature of the JPG file format is that it does not handle transparency; it is only suitable for completely rectangular and opaque images. For transparency support, the PNG file format is highly recommended (it uses a lossless compression algorithm, so the files tend to be bigger, but will not display any compression artifacts or loss of detail).