Joint Photographic Experts Group Format (JPEG)
The JPEG is often used for photos and anything with detailed gradients. There are both advantages and disadvantages to using the JPEG graphics file format.
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Advantages
- Compressed file - Unlike the GIF, the JPEG stores it's color data in values of luminance (brightness) and chrominance (hue). Luminance is more important to our senses than chrominance, therefore more luminance is kept after data compression than chrominance. The actual data compression divides the image into 8x8 pixel squares and calculates a Discrete Cosine Transform (DCT) for that square. Then the DCT coefficients are quantized and a Variable Length Code compression scheme is applied. The quantization step may result in some slight image blurring on sharp edges. There are many different levels of compression available in most graphic software packages. If you have a choice, usually a low to medium level of compression is sufficient and economical for web images. Overall, the final product is a pretty faithful representation of the original and is well suited for the web.
- Unlimited color palette - Unlike the GIF, the color palette is not limited.
- Very effective at recreating photographs, and other natural images.
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Disadvantages
- Usually larger than a GIF image - Due to the different compression algorithm, varying levels of compression, and the unlimited palette, file size is usually larger than a GIF.
- Slight blurring may occur - During compression, sharp edges may become slightly blurred.
- Repeated saves can degrade the image - Due to the compression algorithm of the JPEG, each time you save one, it will degrade slightly since the compression is recalculated.
- Ineffective at recreating digital images with sharp lines and text. Slight artifacting may occur (blemishes in blank space that should not be there).
- Does not support transparency.
- Does not support interlacing.
- Does not support animation.
