lifelike. Quantization for image compression Many image file formats support indexed color. A whole-image palette typically selects 256 "representative" colors for the entire image, where each pixel references any one of the colors in the palette, as in the GIF and PNG file formats. A block palette typically selects 2 or 4 colors for each block of 4x4 pixels, used in BTC, CCC, S2TC, and S3TC. Editor support Many bitmap graphics editors contain built-in support for color quantization, and will automatically perform it when converting an image with many colors to an image format with fewer colors. Most of these implementations allow the user to set exactly the number of desired colors. Examples of such support include: Photoshop's Mode→Indexed Color function supplies a number of quantization algorithms ranging from the fixed Windows system and Web palettes to the proprietary Local and Global algorithms for generating palettes suited to a particular image or images. Paint Shop Pro, in its Colors→Decrease Color Depth dialog, supplies three standard color quantization algorithms: median cut, octree, and the fixed standard "web safe" palette. In GIMP 2.8, the Convert Image to Indexed Colors Option (Image→Mode→Indexed..) allows generation of an optimum palette with a choice in the number of colors from 2 to 256, the option of using a web-optimized palette, using a black and white palette (1 bit) or using a custom palette. It allows unused colors to be removed from the palette and it offers a variety of dithering options: None, Floyd-Steinberg (normal), Floyd-Steinberg (reduced color bleeding) and Positioned as well as the ability to enable dithering of transparency. Color quantization is also used to create posterization effects, although posterization has the slightly different goal of minimizing the number of colors used within the same color space, and typically uses a fixed palette. Some vector graphics editors also utilize color quantization, especially for raster-to-vector techniques that create tracings of bitmap images with the help of edge detection. Inkscape's Path→Trace Bitmap: Multiple Scans: Color function uses octree quantization to create color traces. See also Indexed color Palette (computing) List of software palettes — Adaptive palettes section. Dithering Quantization (image processing) Image segmentation References Further reading Paul S. Heckbert. Color Image Quantization for Frame Buffer Display. ACM SIGGRAPH '82 Proceedings. First publication of the median cut algorithm. Dan Bloomberg. Color quantization using octrees. Leptonica. Oleg Verevka. Color Image Quantization in Windows Systems with Local K-means Algorithm. Proceedings