gammakorrekció

Gammakorrekció, also known as gamma correction, is a nonlinear operation used in image processing and video systems to encode and decode the luminance or intensity of images. It's a way to adjust the brightness and contrast of an image to compensate for the way human vision perceives brightness and how displays reproduce it. Human eyes are more sensitive to changes in darker areas of an image than in brighter areas. Gammakorrekció helps to ensure that the perceived brightness of an image on a display matches the original scene as closely as possible.

In digital imaging, pixel values are typically represented by integers, usually ranging from 0 to 255. A linear relationship between these values and actual luminance would mean that doubling the pixel value results in double the brightness. However, displays do not behave linearly. They often have a "gamma" value, typically around 2.2, which means that a linear increase in input signal does not result in a linear increase in output brightness. Gammakorrekció applies a power-law function to the pixel values to counteract this display characteristic. The formula is often expressed as output = input^(1/gamma).

When an image is captured, it might be encoded with a certain gamma value. When displayed on a screen with a different gamma, the image can appear too dark or too washed out. Gammakorrekció is applied either during image creation (encoding gamma) or just before display (decoding gamma) to correct these discrepancies. For example, if an image is created with a gamma of 2.2, displaying it on a screen with a gamma of 2.2 would generally look correct. However, if displaying on a system that expects a linear signal, the image would need to be adjusted. Conversely, a linearly encoded image might need gamma correction before display on a standard monitor. This process is crucial for achieving consistent and accurate color reproduction across different devices.