What Does JPEG Stand For?
JPEG is an acronym for Joint Photographic Experts Group. JPEG is a standard of compression for images. It is a "lossy" format, which means that when the image is compressed, some of the image data becomes lost. JPEG is ideal for displaying images on the web because it dramatically reduces the file size of the image without significantly reducing the quality.
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Types
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There are three types of JPEG compression: baseline, progressive and lossless. Baseline is merely the original JPEG compression method. Progressive compression saves the file as a series of scans which improve in quality as they progress. Lossless compression is really "effectively lossless." There is a maximum error which is guaranteed to take place between the source image and the destination image.
Features
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If you're using powerful image processing software, you can vary the compression of a JPEG image. Lower compression produces an image with a higher quality, but results in a larger file size. Higher compression reduces the quality of the image but creates a much smaller file. To save an image in JPEG format and control the amount of compression, you will need an image processing program such as Photoshop, Paint Shop Pro or GIMP.
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Function
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JPEG works well when compressing full color or grayscale images. The human eye has difficulty seeing the distortion in a JPEG image. Thus the image looks almost exactly like the original, even though some of the image data has been lost. JPEGs store information in 24-bit color depth, which can contain as many as 16 million colors. GIF, by comparison, is an 8-bit image compression format, which contains just 256 colors. By saving a complex, 24-bit image as a JPEG, there is considerably less distortion than if it were saved as a GIF. The smaller the image is when it is viewed, the less the viewer will be able to see any JPEG distortion.
Benefits
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JPEG format is best for photographs or other images with a smooth, gradual shading. JPEG images not only help to save space on servers, they also reduce bandwidth and download times. The reduction in size of the compressed image is usually significant, even with minimal compression. With a compression rate of just 15 percent, the finished JPEG will typically be about four times smaller than the original. Still, there will be very little noticeable alteration in the picture's appearance.
Considerations
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In some cases, JPEG may distort text or images with bold fields of solid color and line. For these images, use GIF format. JPEG format typically contains blotches called JPEG artifacts which can clearly be seen when the image is magnified. Although these can be reduced with special software, they can't be completely removed. To avoid visible JPEG artifacts in your images, resave your original image with a lower compression rate. Always save your image with a new file name to preserve the original.
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