A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

Aspect Ratio
There are two kinds of aspect ratio that you need to be aware of when working with 2D images; the image aspect ratio and the pixel aspect ratio.The image aspect ratio is the ratio of the width of the image to the height of the image. It's important when resizing an image to keep this ratio as close to unchanged as possible or the image may become distorted.The pixel aspect ratio is the shape of the pixels in the image. For computers this is normally square (1:1) or close to it depending on the monitor settings. For some video sources, however, the pixels may be slightly rectangular.

B

BMP
The Microsoft Windows Bitmap file format is based on the Microsoft Windows internal bitmap data structures. The BMP format is very widely used and it is quick and easy to read. Although most BMP files are uncompressed, a type of run length encoding is supported.

BPP
Bits per pixel.

C

CCITT
CCITT is the most widely used compression scheme for transmitting binary (black and white) image data. CCITT was established by the International Telegraph and Telephone Consultative Committee. The Group 3 and Group 4 CCITT compression standards are widely used for transmitting fax data. CCITT compressed images are typically stored in the TIFF image format.

D

DCX
An image format containing multiple PCX images. A DCX file can contain a maximum of 1024 images.

DDB
Microsoft Device Dependent Bitmap. The actual in-memory information used to display an image.

DIB
Microsoft Device Independent Bitmap. An alternative file extension used by the Microsoft Windows Bitmap.

DEP
Data Execution Prevention (computer security).

F

Float
Denotes a simple type that stores 32-bit floating-point values.

G

GIF
Graphical Interchange File, originally developed by CompuServe as a machine independent format. GIF is one of the most popular image formats for storing 8-bit digitized images. GIF files are typically smaller than uncompressed formats like BMP due to the LZW compression algorithm that GIF uses.

Grey-scale
If the pixels of a grey-scale image have N bits, they may take values from zero, representing black up to 2^N-1, representing white with intermediate values representing increasingly light shades of grey. If N=1, the image is not called grey-scale, but could be called monochrome.

H

Halftone
Pertaining to pictures in which gradation of tone in the photograph is reproduced by a graduated system of dotted and checkered spots, usually nearly invisible to the unaided eye, produced by the interposition between the camera and the object of a screen. The name alludes to the fact that this process was the first that was practically successful in reproducing the half tones of the photograph.

I

ICO
Microsoft Windows Icon file format.

Inverse
To reverse something or change it to its opposite. For example, to invert the colors on a monochrome display means to change light to dark and dark to light. In a digital electrical signal, to replace a high level by a low level and vice versa. This type of operation is the electronic equivalent of a Boolean NOT operation.

J

JIF
An alternative image file extension used for a JFIF compliant JPEG file. Because many early versions of JPEG contained a JPG extension but did not adhere to the JFIF specifications, the JIF extension was created to identify JPEG files that are JFIF compliant. As the popularity of JPEG grew, JFIF compliance became synonymous with the JPG extension and thus the JIF extension is rarely used.

JPEG
The JPEG (Joint Photographic Experts Group) standard is one of the most important image data compression standards. It is widely used in many industries including graphic arts, desktop publishing, medical imaging, and many more. It is also becoming one of the most widely used image formats on the Internet. Although JPEG supports a lossless mode, it most commonly uses lossy compression. This allows JPEG to achieve very high compression ratios. JPEG compression uses several compression modes. First, an image is transformed to the frequency domain using the discrete cosine transform. The smaller valued frequency components are discarded leaving only the larger valued components. The remaining components are DPCM coded and then Huffman coded. Fortunately, ImagXpress™ handles all of this for you! The compression level is adjustable. Higher quality settings produce a larger image file size with higher image quality. Lower quality settings produce a smaller image file size with lower image quality. Typically, we have found that compression ratios of 10:1 or 15:1 (A 640x480x24-bit image is 921,600 bytes; a 15:1 compressed image would compress to only 61k) produce generally acceptable image quality for photographic type images. Images compressed at higher ratios begin to show more noticeable and sometimes objectionable artifacts and clarity loss. JPEG is a 24-bit format and works only with 24-bit images. If you compress an 8-bit image, ImagXpress™ automatically converts it to 24-bit to do the compression, however, you will obtain better quality when the source image is 24-bit because 8-bit images only contain 256 colors. JPEG works best with photographic type images. It does not work well with solid colors, 16-color images, cartoon like images, or drawings. Progressive JPEG is a multiple-scan sequential JPEG format that is becoming popular on the Internet for the ability to display images in progressively clearer segments.

L

LZW
Lempel-Ziv-Welch (algorithm).

Little-endian
Describes a computer architecture in which, within a given 16- or 32-bit word, bytes at lower addresses have lower significance (the word is stored "little-end-first"). The PDP-11/VAX families of computers, Intel microprocessors, plus a lot of communications and networking hardware are little-endian. The term is sometimes used to describe the ordering of units other than bytes; most often, bits within a byte.

Luminance
One of the 3 components of the HSL (Hue, Saturation and Luminance) color space. Luminance controls the overall brightness of an image.

P

PBM
Portable bitmap image format, a very simple uncompressed 1-bit (black and white) image format.

PGM
Portable Graymap image format. PGM is a very simple uncompressed 8-bit grayscale image format.

PNG
Portable Network Graphics (pronounced "ping") provides a portable, legally unencumbered (royalty-free), well-compressed, well-specified standard for lossless bitmapped image files. The initial motivation for developing PNG was to provide a royalty-free alternative to GIF. The design retains many of the features of GIF that make it an attractive format for transmission of images, such as lossless compression and progressive display capabilities. Additionally, it provides several advantages including 24-bit image support and generally better compression, although decompression is typically somewhat slower than GIF.

PPM
Portable Pixmap image format, a very simple uncompressed 24-bit image format.

R

RLE
RLE stands for Run Length Encoding. It is a lossless algorithm that only offers decent compression ratios in specific types of data.

RGB
Red Green Blue. Bitmapped images are most generally stored as RGB data. Each pixel or data point in a true color (24-bit) image contains 3 components, red, green and blue, that describe the color of the pixel. Each of the components can have a value between 0 and 255, 0 being the darkest shade of color and 255 being the lightest shade of color. Since each component can be stored in one byte (8-bits), the 3 components take up 3 bytes or 24-bits per pixel. 8-bit images contain one byte (8-bit) indexes for each pixel that map to a color table called a palette which contains a maximum of 256 RGB entries. Likewise, 4-bit images contain 4-bit indexes for each pixel that map to a palette which contains a maximum of 16 RGB entries. 1-bit images contain 1-bit per pixel. Each bit in a 1-bit image represents either black or white.

T

twip
Twips describe the sizes of characters produced by dot matrix printers, which were constrained to multiples of either 12 or 10 dots per inch.

TGA
Targa Image File) format was developed by TrueVision for its Targa line of products. TGA is one of the earliest image formats and was the first popular format to support 24-bit color. TGA supports uncompressed and RLE compressed formats.

TIFF
Tag Image File Format, originally released by Aldus Corporation is a standard file format found in most paint, imaging, and desktop publishing programs. TIFF is extremely powerful, flexible, and extensible. However, because of its many nuances and its wide scope, TIFF can be a difficult format to understand as well as a difficult format to support. ImagXpress™ supports a wide range of TIFF 6.0 formats including uncompressed, CCITT RLE, CCITT Group 3 Fax, CCITT Group 4 Fax, LZW, Pack Bits, JPEG, and deflate compression types. ImagXpress™ supports black and white, RGB, and RGB palette images but it does not support transparency mask, CMYK, YCbCr, or CIELab.

W

WMF
The Microsoft Windows Metafile format is used to store vector and bitmap image data. Because of its popularity and wide use, many Windows and non-Windows applications support WMF.

Wintel
A term describing the combination of Microsoft Windows operating system running on PCs with Intel or compatible processors. Dominance of the wintel platform began with MS-DOS on PCs with Intel's 8-bit 8088 processors in 1979.