5(1991)Type of formatPCX image formats Table A. Common PCX Image FormatsBit DepthPlanesNumber of Colors4116 colors from a palette81256 colors from a palette81256 shades of gray444095 colors with 16 levels of transparency8316.7 million, 24-bit 'true color'8416.7 million with 256 levels of transparencyPCX was designed during the early development of PC display hardware and most of the formats it supported are no longer used, Table A shows a list of the most commonly used PCX formats. Contemporary image editing programs may not read PCX files that match older hardware.PCX is supported by common image processing software including,. In version 2.1.4 could encode and decode the PCX pixel formats rgb24, rgb8, bgr8, rgb4byte, bgr4byte, gray, pal8, and monob.There is a multi-page version of PCX, used by some computer and document management programs, with file extension.dcx. A DCX file consists of a header introducing a set of following PCX files. PCX file formatPCX files were designed for use on IBM-compatible PCs and always use byte ordering. A PCX file has three main sections, in the following order.
128-byte header. image data. (optional) 256-color paletteThe PCX file header contains an identifier byte (value 10), a version number, image dimensions, 16 palette colors, number color planes, bit depth of each plane, and a value for compression method.
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PCX version numbers range from 0 to 5, this originally denoted the version of the program used to create the PCX file. The header always has space for 16 colors though the number of colors used depends upon the bit depth of the image. The header is 74 bytes long and the image data begins 128 bytes after the start of the file, the 54 bytes between are not used.All PCX files use the same compression scheme and the compression value is always 1. No other values have been defined and there are no uncompressed PCX files. One source claims that 0 (uncompressed) is allowed, but not much software supports it. Image data layout Table B. PCX Image Data Arranged into Color PlanesRow 0R R R R R R R R RG G G G G G G GB B B B B B B B BA A A A A A A A ARow 1R R R R R R R R RG G G G G G G GB B B B B B B B BA A A A A A A A ARow 2 etc.PCX image data is stored in rows or scan lines in top-down order.
If the image has multiple planes, these are stored by plane within row, such that all the red data for row 0 are followed by all the green data for row 0, then all the blue data, then alpha data. This pattern is repeated for each line as shown in Table B.When an image is less than 8 bits per pixel, each line is padded to the next byte boundary.
For example, if an image has 1 plane of 1-bit data (monochrome) with a width of 22 pixels, each row will be 3 bytes long, having 24 bits per row with 2 bits unused.Image data compressionPCX image data are compressed using (RLE), a simple algorithm that collapses a series of three or more consecutive bytes with identical values into a two-byte pair. The two most-significant bits of a byte are used to determine whether the given data represent a single of a given palette index or color value, or an RLE pair representing a series of several pixels of a single value. Rettungswagen simulator 2012 patch pc.