Jpeg Compression

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Uncompressed Image Let us first consider how much memory an uncompressed bitmap raster image uses. Using a desktop 1280 x 1024 pixel image for example. Each pixel requires 3 memory locations to store the RGB colours. So 3 Blocks ( arrays-grids) of 1280 x 1024 memory are used = 3932160 memory locations. Therefore any 1280 x 1024 image will always use 3932160 memory locations. The old Windows Paint bmp file format stores uncompressed data plus some header info. The Header is typically 50 bytes and contains a file type marker for picture editors to identify the image to process along with other info such as width, depth, number of colours, 8-bit or 16-bit, etc . The RGB image data follows in a sequence until the end of the image. The video data may contain padding bytes to make the image line an even number of pixels. With larger images the huge file sizes create a problem for data storage and transmission over networks. To overcome these problems data compression is used to reduce the file size.