Format name: PCX (PC Paintbrush File format)
Compression algorithm: RLE, without compression
Color depth: 1, 4, 8, 24 bits
PCX format is one of the most usable graphic formats. Originally it was designed by Zsoft for PC Paintbrush MS-DOS. That is why, it is also known as PC Paintbrush format. Zsoft entered into a treaty with Microsoft. The latter was entitled to use PCX format with other products, including Microsoft Paintbrush for Windows (Microsoft Paintbrush program is delivered with each copy of MS Windows). As a result, the format became of great importance not only for computers, based on Intel processors, but also for the whole computer industry.
PCX files are used for graphic data storage and exchange in desktop publishing system.
Originally the format was used to hold graphics and images, which contained not more than 16 colors. This limitation was conditioned by IBM EGA display construction (Enhanced Graphics). When IBM started to release VGA adapter (Virtual Graphics Array), PCX format was revised to hold graphics and images, which contained up to 256 colors.
The last PCX versions make possible to hold 24 bits color displays. Due to this fact, the format can be generally used for graphic data operating. Unfortunately, its compression algorithm is not effective enough to hold images with large pixel intensity (read more about compression algorithms here).
Image data are encoded with the help of one of the RLE algorithm variants (read more about this compression algorithm here). Using RLE algorithms, it is difficult to foresee the end, for compressing factor is highly depended on image data and on the number of colors, used in the concrete. Generally, image data, which contain not more than 16 colors, decrease by 40-70% as compared with the original file size. While 64 or 256 color images, which were scanned or videoed, decrease only by 10-30%. Sometimes you can increase PCX file size via using compression algorithm for complex images.