Help Glossary - GreycLab/gmic-community GitHub Wiki

List of terms used in the Help Files which may be unknown to the reader, or have different meanings when used in a discussion relating to computer images, vs. use in every day society. Any word, term, expression, or phrase used in any help file which is ambiguous, technical, or obscure should be listed herein. This is an ever expanding project began on 8 February, 2016. If something is missing, it may not have been gotten to yet.

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  •  Grayscale -- See Greyscale

  •  Greyscale -- This refers to an image type whose colors are all shades of grey. An old fashioned black and white photograph is actually of this type. True Greyscale images use one byte per pixel to store color information, with a value of 0 representing black, and a value of 255 indicating White. This form however is almost never seen as an image, but is frequently used to convey data. For example altitude data in a topographical map.
    Usually seen are greyscale images which use the RGB or RGBA form of storing their colors. In these uses the R, G, and B values all have identical values, which result in a shade of grey, between black and white, and a possible Alpha component, which refers to it's level of opacity.

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  •  RGB -- This term refers to a color code format used most image manipulation programs, and most file formats (like .gif, .jpeg, .png, etc). The R, G, and B refer to integer values in the range of 0 to 255, which indicate "how much" Red, Green, and Blue color appear in the pixel in question.
    Images of this type have no transparency associated with them.

  •  RGBA -- This expanded form of RGB notation adds another byte to the color description which represents the pixels opacity. A value of 0 indicates the pixel is totally transparent, while 255 indicates it is totally opaque (non-see-through).
    Images of this type are usually .gif, or .png.
    This is the primary format used by The GIMP, and most modern image editing software.

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