The XCF file format is an image file created by the GNU Image Manipulation Program (GIMP), a freely distributed image editing program. XCF files are similar in makeup to a Photoshop PSD, supporting layers, channels, transparency, paths and guides. The XCF file format is backward compatible (all versions of GIMP can open earlier versions' files) and in some cases, forward compatible. Using XCF as for data interchange is not recommended by the developers of GIMP, as there may be format changes in future versions and XCF reflects various internal data structures for GIMP.
The XCF format is designed to store the entire part of the state of the Gimp that is specific to one image, apart from undo data. An XCF file is a sequence of bytes which describes a stack of layers and channels on a canvas, which is effectively just a rectangular viewport for the layers and channels. It contains a series of data structures with the main image structure coming at the very beginning of the file. The first 9 bytes of an XCF file are the ASCII string "gimp xcf "
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eXperimental Computing Facility of the University of California at Berkeley
PNG pronounced ping is a format for storing bitmapped (raster) images on computers. It was created originally to replace the GIF file format when it was announced that the companies who created the GIF format wanted royalties. PNG uses indexed colors and lossless compression (like a .GIF file), but without those copyright limitations; it cannot be animated like a GIF image.
PNG images are in many ways better than .GIF as they also include an 8-bit transparency channel, which allows the colors in the image to fade from opaque to transparent; GIF images only support fully opaque or fully transparent pixels. PNG supports palettes of 24-bit RGB colors, RGB images or greyscale or RGB images. PNG was intended to be able to transfer images on the Internet, not professional graphics, and so does not support other colour spaces (such as CMYK).
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