Storage of raster images and compression types, Raster...

Storing Bitmap Images and Compression Types

Bitmap images are generally stored in compressed form. Compression ( Compression ) Images is an application algorithms for compressing data to images stored in digital form. As a result of compression, the image size is reduced, which reduces the time of image transmission over the network and saves storage space. Compression types usually predetermine the possibility or impossibility of image recovery exactly as it was before compression (lossless compression or lossy compression, respectively). Also in the graphic file can be stored additional information: the author of the file, the camera and its settings, the number of dots per inch when printing, etc.

Lossless compression uses compression algorithms based on reducing redundancy.

Lossy compression is based on discarding a piece of information, usually the least perceived by the eye.

Raster graphic formats

BMP (from English Bitmap Picture) , or Windows strong> Bitmap , is a bitmap storage format developed by Microsoft. BMP is commonly used without compression, although compression is possible. With the BMP format, a huge number of programs work, since its support is integrated into the operating systems Windows and 05/2. BMP files can have .bmp, .dib, and .rle extensions.

ICO (English Windows icon) - the format for storing file icons in Microsoft Windows < strong>.

GIF (from English Graphics Interchange Format - a format for sharing images) is a widely used graphics format. It is able to store compressed data without loss of quality in a format of not more than 256 colors. Hardware-independent GIF format was developed in 1987 (GIF87a) by CompuServe to transfer raster images over networks. In 1989, the format was modified (GIF89a), support for transparency and animation was added. For a long time GIF was one of the most common formats on the Internet. Now GIF is an obsolete format, still popular because of animation support.

PNG Network Graphics) is a popular raster format for storing graphic information using lossless compression. PNG was created as a free format to replace GIF. Widely used on the Internet.

PCX (PCExchange ) is a standard for presenting graphical information. It was used by the graphic program ZSoft PC Paintbrush (one of the first popular graphics software) for MS DOS, word processors and desktop publishing systems, such as Microsoft Word and Ventura Publisher . PCX is an obsolete format that allows you to easily compress simple drawing images (when you compress a group of consecutive pixels of the same color are replaced by a record of the number of such pixels and their color). Not so popular as BMP, although supported by major image editors, such as Adobe Photoshop, CorelDRA, W, , GIMP , etc. Now it is superseded by formats that support better compression: GIF, JPEG and PNG.

JPEG is one of the popular image formats used to store photos and similar images. Files containing JPEG data usually have .jpeg, .jfif, .jpg, JPG, or JPE extensions. However, of them .jpg is the most popular on all platforms. JPEG is very widely used. The compression is based on the averaging of the color of neighboring pixels (information on the brightness is then averaged) and the rejection of high-frequency components in the spatial spectrum of the image fragment. When examining a highly compressed image in detail, noticeably blurring of sharp boundaries and a characteristic moiré near them.

JPEG 2000 (or jp2) is a graphic format that uses a different compression type than J PEG. As a result of this compression, the image is smoother and crisper, and the file size is smaller compared to JPEG for the same quality. Extension, jp2, j2k, .jpf, .jpx, jpm, .wdp.

JPEG XR (formerly called I ID Photo and Windows Media Photo ) - encoding format and file format for photos. The extension .jxr, .hdp, .wdp.

PSD is a raster format for storing graphic information using lossless compression, created specifically for Adobe Photoshop and supports all its features.

TIFF (English Tagged Image Pile Format) - the format for storing raster graphics. TIFF has become a popular format for storing images with a large depth of color. It is used for scanning, sending faxes, recognizing text, printing, widely supported by graphics applications. Initially, the format supported lossless compression, was later added to support compression with loss in the format of JPEG. TIFF allows you to achieve a large range of color depth changes, has different color spaces, different compression settings (both with or without loss), etc. TIFF files have a .tif or .tiff extension.

WebP is a lossy and lossless image compression format offered by Google Inc . in 2010

XPS (English XML Paper Specification) is an open, fixed-format graphic format on the XML database developed by Microsoft. The functionality is exclusively for document management - the document is simpler and easier than PDF.

RLA is a raster format that allows you to save three-dimensional images by including arbitrary channels selected by the user in the output file. In 3d Max, the RLA format is used as input and output. In this case, it allows the formation of transparent areas in the stored images.

TGA (English Truevision TSL ) is a raster graphic format created by Truevision Inc . for graphics adapters of its own production in 1984. Later it became popular on a variety of platforms, especially in the field of video processing and animation.

RPF (Pixel Fomat File) - has the same capabilities as RLA. This format is used when the rendered animation requires further processing or adding effects. The RPF format supports a large number of channels that are not available in other cases.

We did not consider all formats of raster graphics, we note the most common:

• lossless compression: BMP, FPX, GIF, ICO, ILBM, JBIG, PCX, PNG, PNM, PSD, RAW, TGA, WBMP, XCF;

• lossy compression: EXR, ICER, JBIG2, JPEG (JP2, JPFG-LS), JPEG XR (HD Photo), PGF, TIFF, WebP;

• Animation: APNG, GIF, MNG.

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