JPEG, JPG

JPEG stands for Joint Photographic Experts Group. This is the name of the committee that wrote the JPEG standard. JPEG is a file format that has been developed specifically for compressing photographic images. JPEG is the file format to use for any type of photograph. For photos, JPEG works better than any other file format. On the other hand, JPEG is not really suited for compressing images that contain lettering or line drawings such as logos and cartoons. For these type of images, you are better off using GIF or PNG, rather than the JPEG format.

JPEG is a lossy file format. This means that the images may be slightly changed when you compress it using the JPEG algorithms. In other words, JPEG causes the image to lose some data. Obviously, there may be some disadvantages in that. On the other hand, JPEG achieves very high compression ratios just because of that. In fact, the JPEG compression ratio is higher than what could be achieved with lossless compression.

The human eye perceives small colour changes less accurately than changes in brightness. JPEG has been designed to exploit this and other limitations of the human eye. So the compression algorithm has been designed to lose some data where this will not be perceived by the human eye.

When compressing images using the JPEG format, the designer can usually decide how much data is lost. Obviously, the JPEG image will look better if less information is lost. On the other hand, such images will also be better. So it is up to the graphic designer to strike the right balance and make the JPEG image look great while making it as small as possible.