This glossary is still in progress.  Be sure to check back for more entries.  They will be added regularly. 

Alpha Channel : An alpha channel is the part of an image that describes transparency.

Aspect Ratio : Aspect ratio refers to the ratio (%) of the width to the height of an image.

Bitmap : a bitmap image is comprised of bits -- also called pixels.  Bits are tiny square portions that make up the image.  Each one is a color.   Bitmap images cannot be made larger without losing resolution (quality).   Bitmap is also the name of an image format.  The file extension in the image format "bitmap" is .bmp.  

Color Depth, also called Pixal Depth :  The color depth of an image is the amount of colors that it contains.  Common color depths are 256 colors, 16-bit (65,000 colors), 24-bit (true color), and 32-bit (millions of colors).  The more color depth an image contains, the more realistic it displays.    Also, the higher the color depth, the larger the file size in kilobytes. 

File Extensions:  A file extension is the portion after the period in a file name.  This applies to any file type, not just images.   For example: a file with the name of image.jpg has the jpg file extension.  It means that the image is formatted as jpg (pronouced jay-peg).   Think of the file extension as the "language" the file format is saved in.  In order to view the file, the program that you are using must know how to "speak" that file's language.    Common file extensions for images are jpg, gif, tiff, png and bmp.   To see a table of graphic formats, click here. 

Graphics: The word graphics is used to refer to pictures, icons, photographs, charts and glyphs (to name a few) when they are used and created on computers. 

Halftone : halftone is using small dots of various sizes and spacing to reproduce the shades and textures of a continous tone image.   A good example would be old newspaper images. 

Icon : an icon, in graphic terms, is a small image representation of something.  Icons are used on Window's desktops as links to programs and as a representation of a file type.   They are used as links to programs, commands and file types.  An icon can also be a smilie or a picture used for messenger clients called a "buddy icon". 

JPEG or JPG : an acronym for Joint Photographic Electronic Group, is an image file format that compresses an image.  It is considered a "lossy" format because when it is used, the image loses quality.  One can set the amount of compression to use when creating or saving jpg images from 1 (almost no compression) to 100 (fully compressed).  The more compressed the image, the smaller the file size. 

Mask :  a mask is a grayscale image on a layer, also known as a channel mask -- the white areas are 100% opaque (solid) and the black areas are 100% transparent (see-through) with the shades of gray inbetween having variable transparency depending upon the percentage of black or white.  The darker the shade, the more transparent.   The lighter the shade, the more opaque. 

PSP:  Before Sony's Playstation Portable, PSP was Paint Shop Pro.   Now, there might be some confusion.   So, in the gaming world, PSP is Sony's hot little game, in Graphics, it's Paint Shop Pro. 

PSP Tube : Paint Shop Pro picture tube file.   They are used as a tool in Paint Shop Pro.  They allow you to place an image (the tube) anywhere on your image.   Tube files can contain anywhere from 1 image to an endless number of them.  

RGB : acronym for red, green and blue.

TIFF:  a bitmap image format with no loss of quality, for continous tone photographs and image.  It is an acronym for tagged image file format. 

Transparency : a part of an image that is invisible.   Transparency in an image can range from completely invisible to nearly opaque. 

Resolution :  resolution is the number of pixels present in a square inch of an image.  The more pixels in a square inch, the better the quality.   Web graphics use 72 ppi (pixels per inch).   In professional printing, a common resolution is 300 ppi. 

Vector:  vector graphics are an image format that uses mathmatically defined shapes instead of pixels.  Vector graphics can be resized without loss of quality.  They have a smaller file size than their bitmap (rasterized) counterparts.