Gray value

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In typography as in image processing, the gray value describes the apparent brightness of a text or an image or an individual pixel. It therefore indicates how light or dark the object in question appears to the human eye .

In typography

In the typography of the gray value is mainly by line width , walking distance , word spacing, line length and line spacing or leading determined. It is ideal if all these features are coordinated so that the text is optimally legible.

The gray value can then e.g. B. used for comparison with a threshold value in a threshold value method.

In image processing

In image processing , the gray value represents the brightness or intensity value of an individual pixel. In the case of an RGB color value, the formula

Gray value = 0.299 × red component + 0.587 × green component + 0.114 × blue component

the gray value can be calculated. The result is a value that reflects the brightness of the pixel regardless of the colors . The percentage distribution of the weighting of the 3 colors is related to the corresponding color sensitivity of the eyes. In image processing practice, however, this distribution is sometimes ignored and all three color channels are weighted equally.

In television technology, the gray value signal (luminance signal) is still used today in the composite video signal in order to be compatible with the old BAS signal (black and white).

  • Original image

  • Gray color image with channel weighting

  • Gray color image without channel weighting

See also

Web links

  • Gray value - definition in the lexicon of Western European typography.