The JPEG filename extension is JPG or JPEG. JPEG (Joint Photographic Experts Group) is a lossy compression method JPEG-compressed images are usually stored in the JFIF (JPEG File Interchange Format) or the Exif (Exchangeable image file format) file format. Examples are PostScript, PDF and PCL.įurther information: Raster graphics Delivery formats JPEG Page description language refers to formats used to describe the layout of a printed page containing text, objects and images. Most applications open metafiles and then save them in their own native format. The metafile format is an intermediate format. Examples are application-independent formats such as WMF and EMF. In addition to straight image formats, Metafile formats are portable formats which can include both raster and vector information. supporting relatively strong compression) versus formats primarily aimed at authoring or interchange (uncompressed or only relatively weak compression). Raster images are further divided into formats primarily aimed at (web) delivery (i.e. Some of these graphic formats are listed and briefly described below, separated into the two main families of graphics: raster and vector. The PNG, JPEG, and GIF formats are most often used to display images on the Internet. Including proprietary types, there are hundreds of image file types. Most lossy compression algorithms allow for variable compression that trades image quality for file size. Often lossy compression is able to achieve smaller file sizes than lossless compression. Lossy compression algorithms preserve a representation of the original uncompressed image that may appear to be a perfect copy, but is not a perfect copy. Lossless compression should be used to avoid accumulating stages of re-compression when editing images. Lossless compression generally, but not always, results in larger files than lossy compression. Lossless compression algorithms reduce file size while preserving a perfect copy of the original uncompressed image. There are two types of image file compression algorithms: lossless and lossy. With vector images, the file size increases only with the addition of more vectors. images with large continuous regions like line art or animation sequences) may be losslessly compressed into a GIF or PNG format and result in a smaller file size than a lossy JPEG format.įor example, a 640 × 480 pixel image with 24-bit color would occupy almost a megabyte of space:Ħ40 × 480 × 24 = 7,372,800 bits = 921,600 bytes = 900 KiB For example, graphically simple images (i.e. This characteristic sometimes results in a smaller file size for some lossless formats than lossy formats. With some compression formats, images that are less complex may result in smaller compressed file sizes. Considering exactly the same compression, number of pixels, and color depth for two images, different graphical complexity of the original images may also result in very different file sizes after compression due to the nature of compression algorithms. Images with the same number of pixels and color depth can have very different compressed file size. A compression algorithm stores either an exact representation or an approximation of the original image in a smaller number of bytes that can be expanded back to its uncompressed form with a corresponding decompression algorithm. Images can be compressed in various ways, however. The size of raster image files is positively correlated with the number of pixels in the image and the color depth (bits per pixel). A common method for displaying digital image information has historically been rasterization. Image files are composed of digital data in one of these formats so that the data can be displayed on a digital (computer) display or printed out using a printer. A 3D image can be represented within a 2D format, as in a stereogram or autostereogram, but this 3D image will not be a true light field, and thereby may cause the vergence-accommodation conflict. Some image file formats support transparency. For graphic design applications, vector formats are often used. If the data is compressed, it may be done so using lossy compression or lossless compression. The data stored in an image file format may be compressed or uncompressed. Most formats up until 2022 were for storing 2D images, not 3D ones. There are many formats that can be used, such as JPEG, PNG, and GIF. For the camera sensor format, see Image sensor format.Īn image file format is a file format for a digital image.
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