In computer graphics, a bitmap or pixmap is a type of memory organization or image file format used to store digital images. Computer graphics are Graphics created by Computers and more generally the Representation and Manipulation of Pictorial Data Computer data storage, often called storage or memory, refers to Computer components devices and recording media that retain digital This is a comparison of Image file formats. General Ownership of the format and related information A digital image is a representation of a two-dimensional Image using ones and zeros (binary The term bitmap comes from the computer programming terminology, meaning just a map of bits, a spatially mapped array of bits. A bit array (or bitmap, in some cases is an Array Data structure which compactly stores individual bits ( Boolean values. Now, along with pixmap, it commonly refers to the similar concept of a spatially mapped array of pixels. In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image Raster images in general may be referred to as bitmaps or pixmaps, whether synthetic or photographic, in files or in memory. In Computer graphics, a raster graphics image or bitmap, is a Data structure representing a generally rectangular grid of Pixels

In some contexts, the term bitmap implies one bit per pixel, while pixmap is used for images with multiple bits per pixel. ^[1][2]

Many graphical user interfaces use bitmaps in their built-in graphics subsystems;^[3] for example, the Microsoft Windows and OS/2 platforms' GDI subsystem, where the specific format used is the Windows and OS/2 bitmap file format, usually named with the file extension of . Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. OS/2 is a computer Operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively The Graphics Device Interface (GDI is one of the three core components or "subsystems" together with the kernel and the Windows API for the user interface A filename extension is a suffix to the name of a Computer file applied to indicate the encoding convention ( File format) of its contents BMP (or . DIB for device-independent bitmap). Besides BMP, other file formats that store literal bitmaps include InterLeaved Bitmap (ILBM), Portable Bitmap (PBM), X Bitmap (XBM), and Wireless Application Protocol Bitmap (WBMP). ILBM is a subtype of the Interchange File Format (IFF used for storing picture data The portable pixmap file format ( PPM) the portable graymap file format ( PGM) and the portable bitmap file format ( PBM) specify rules In Computer graphics, the X Window System uses X BitMap ( XBM) an ASCII text Monochrome image format, for storing Wireless Application Protocol Bitmap Format (shortened to Wireless Bitmap and with file extension. Most other image file formats, such as JPEG, TIFF, PNG, and GIF, to name just a few, store bitmap images (as opposed to vector images), but they are not usually referred to as bitmaps, since they use compressed formats internally. Portable Network Graphics ( PNG) is a bitmapped image format that employs Lossless data compression. Image compression is the application of Data compression on Digital images In effect the objective is to reduce redundancy of the image data in order to be able to

Pixel storage

In typical uncompressed bitmaps, image pixels are generally stored with a color depth of 1, 4, 8, 16, 24, 32, 48, or 64 bits per pixel. Image compression is the application of Data compression on Digital images In effect the objective is to reduce redundancy of the image data in order to be able to In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image Color depth. or bit depth, is a Computer graphics term describing the number of Bits used to represent the Color of a single Pixel Pixels of 8 bits and fewer can represent either grayscale or indexed color. In Computing, a grayscale or greyscale Digital image is an image in which the value of each Pixel In computing indexed color is a technique to manage Digital images colors in a limited fashion in order to save computer's memory and file storage An alpha channel (for transparency) may be stored in a separate bitmap, where it is similar to a greyscale bitmap, or in a fourth channel that, for example, converts 24-bit images to 32 bits per pixel. In Computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial transparency Transparency is possible in a number of graphics file formats In Computing, a grayscale or greyscale Digital image is an image in which the value of each Pixel

The bits representing the bitmap pixels may be packed or unpacked (spaced out to byte or word boundaries), depending on the format or device requirements. Data structure alignment is the way data is arranged and accessed in computer memory Depending on the color depth, a pixel in the picture will occupy at least n/8 bytes, where n is the bit depth.

For an uncompressed, packed within rows, bitmap, such as is stored in Microsoft DIB or BMP file format, or in uncompressed TIFF format, the approximate size for a n-bit-per-pixel (2ⁿ colors) bitmap, in bytes, can be calculated as:

, where height and width are given in pixels. The BMP file format, sometimes called bitmap or DIB file format (for device-independent bitmap) is an Image file format used to store A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image

In the formula above, header size and color palette size, if any, are not included. Due to effects of row padding to align each row start to a storage unit boundary such as a word, additional bytes may be needed. A word is a unit of Language that carries meaning and consists of one or more Morphemes which are linked more or less tightly together and has a Phonetic

Device-independent bitmaps and BMP file format

Main article: BMP file format

Microsoft has defined a particular representation of color bitmaps of different color depths, as an aid to exchanging bitmaps between devices and applications with a variety of internal representations. The BMP file format, sometimes called bitmap or DIB file format (for device-independent bitmap) is an Image file format used to store They called these device-independent bitmaps or DIBs, and the file format for them is called DIB file format or BMP file format. The BMP file format, sometimes called bitmap or DIB file format (for device-independent bitmap) is an Image file format used to store According to Microsoft support:^[4]

A device-independent bitmap (DIB) is a format used to define device-independent bitmaps in various color resolutions. The main purpose of DIBs is to allow bitmaps to be moved from one device to another (hence, the device-independent part of the name). A DIB is an external format, in contrast to a device-dependent bitmap, which appears in the system as a bitmap object (created by an application. . . ). A DIB is normally transported in metafiles (usually using the StretchDIBits() function), BMP files, and the Clipboard (CF_DIB data format).

Here, "device independent" refers to the format, or storage arrangement, and should not be confused with device-independent color. In digital imaging systems color management is the controlled conversion between the Color representations of various devices such as Image scanners Digital

Other bitmap file formats

Main article: Image file formats

The X Window System uses a similar XBM format for black-and-white images, and XPM (pixelmap) for color images. Image file formats are standardized means of organising and storing images In Computer graphics, the X Window System uses X BitMap ( XBM) an ASCII text Monochrome image format, for storing Black-and-white is a number of Monochrome forms in Visual arts. X Pixmap ( XPM) is an ASCII -text-based image format used by the X Window System. Numerous other uncompressed bitmap file formats are in use, though most not widely. ^[5] Much more common are the standardized compressed bitmap files such as GIF, PNG, TIFF, and JPEG. Portable Network Graphics ( PNG) is a bitmapped image format that employs Lossless data compression. ^[6] TIFF and JPEG have various options. JPEG is usually lossy compression. TIFF is usually either uncompressed, or losslessly Lempel-Ziv-Welch compressed like GIF. Lempel-Ziv-Welch ( LZW) is a universal Lossless data compression Algorithm created by Abraham Lempel, Jacob Ziv, and Terry PNG uses deflate lossless compression, another Lempel-Ziv variant. Lempel-Ziv-Welch ( LZW) is a universal Lossless data compression Algorithm created by Abraham Lempel, Jacob Ziv, and Terry

There are also a variety of "raw" image files, which store raw bitmaps with no other information; such raw files are just bitmaps in files, often with no header or size information, and should not be confused with photographic raw image formats, which store raw unprocessed sensor data in a structured container such as TIFF format along with extensive image metadata. A raw image file contains minimally processed data from the image sensor of a Digital camera or Image scanner. Metadata ( meta data, or sometimes metainformation) is "data about data" of any sort in any media

See also

• Raster graphics
• Raster scan

References