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Sometimes, you find a drawing or similar image useful for a Wikipedia article, that was saved as a JPEG but should have been saved as a PNG.JPEG is good for images where the color changes fluidly throughout the image, like in a photograph, whereas PNG files are good for images with relatively few colors, such as a drawing of a flag, a chart, or a map; note that sometimes SVG is better.
A 2-bit indexed color image. The color of each pixel is represented by a number; each number (the index) corresponds to a color in the color table (the palette).. In computing, indexed color is a technique to manage digital images' colors in a limited fashion, in order to save computer memory and file storage, while speeding up display refresh and file transfers.
The main use of pngcrush is for reducing the size of the image data contained in the IDAT section. The pixel data in a PNG file is compressed using LZ77 algorithm (which tries to find repeated byte sequences in the source data), and then further compressed with Huffman algorithm. This combination is referred to as deflate compression. Before ...
Thus a truecolor PNG is typically larger than a color-reduced GIF, although PNG could store the color-reduced version as a palettized file of comparable size. Conversely, some tools, when saving images as PNGs, automatically save them as truecolor, even if the original data use only 8-bit color, thus bloating the file unnecessarily. [ 55 ]
The X Window System uses a similar XBM format for black-and-white images, and XPM (pixelmap) for color images. Numerous other uncompressed bitmap file formats are in use, though most not widely. [7] For most purposes, standardized compressed bitmap files such as GIF, PNG, TIFF, and JPEG are used.
WebP is a raster graphics file format developed by Google intended as a replacement for JPEG, PNG, and GIF file formats. It supports both lossy and lossless compression, [8] as well as animation and alpha transparency.
The PNG file format supports 8-bit (256 colors) paletted images (with optional transparency for all palette colors) and 24-bit truecolor (16 million colors) or 48-bit truecolor with and without alpha channel – while GIF supports only 8-bit palettes with a single transparent color. Compared to JPEG, PNG excels when the image has large ...
In addition, transparency is often an "extra" for a graphics format, and some graphics programs will ignore the transparency. Animated PNG 8-bit transparency. Raster file formats that support transparency include GIF, PNG, BMP, TIFF, TGA and JPEG 2000, through either a transparent color or an alpha channel.