Image Formats

JPEG Image Format

The JPEG (Joint Photographic Experts Group)

This format is designed for storing photographic images with millions of colors at different compression rates.

During compression, graphics programs use special algorithms to sample and render colors close to those in the original picture but without retaining full color information in order to minimize file sizes.

You normally have a choice of compression settings when saving pictures in JPEG format. Smaller file sizes normally mean greater loss of picture details. Still, with moderate compression you can display an image on screen that appears very similar in quality to the original picture.

The four pictures below show the original image and three compressions along with resulting file sizes.You can notice a loss of sharpness in those images with higher compressions and smaller file sizes.

JPEG images at various compressions

For Web images that are displayed at normal 72 pixels per inch, compression percentages that reduce file sizes to as small as 1/8 to 1/4 of original file sizes still retain satisfactory visual precision.

JPEG images are saved as files with the .jpg extension. JPEG format does not support interlacing or transparency; plus, it is not a good format for text or line drawings since the precision needed to produce straight lines or hard edges is not as accurate with compression.

JPEG image with High Compression[Low Quality]
JPEG image with Low Compression [High Quality]