FreeImage.GetAdjustColorsLookupTable Method

public static int GetAdjustColorsLookupTable(
	byte[] lookUpTable,
	double brightness,
	double contrast,
	double gamma,
	bool invert
)

Parameters

lookUpTable

Type: SystemByte
Output lookup table to be used with AdjustCurve(FIBITMAP, Byte, FREE_IMAGE_COLOR_CHANNEL). The size of 'lookUpTable' is assumed to be 256.

brightness

Type: SystemDouble
Percentage brightness value where -100 <= brightness <= 100.

A value of 0 means no change, less than 0 will make the image darker and greater than 0 will make the image brighter.

contrast

Type: SystemDouble
Percentage contrast value where -100 <= contrast <= 100.

A value of 0 means no change, less than 0 will decrease the contrast and greater than 0 will increase the contrast of the image.

gamma

Type: SystemDouble
Gamma value to be used for gamma correction.

A value of 1.0 leaves the image alone, less than one darkens it, and greater than one lightens it.

invert

Type: SystemBoolean
If set to true, the image will be inverted.

Return Value

Furthermore, the lookup table created does not depend on the order, in which each single adjustment operation is performed. Due to rounding and byte casting issues, it actually matters in which order individual adjustment operations are performed. Both of the following snippets most likely produce different results:

// snippet 1: contrast, brightness
AdjustContrast(dib, 15.0);
AdjustBrightness(dib, 50.0);

// snippet 2: brightness, contrast
AdjustBrightness(dib, 50.0);
AdjustContrast(dib, 15.0);

Better and even faster would be snippet 3:

// snippet 3:
byte[] lut = new byte[256];
GetAdjustColorsLookupTable(lut, 50.0, 15.0, 1.0, false);
AdjustCurve(dib, lut, FREE_IMAGE_COLOR_CHANNEL.FICC_RGB);

This function is also used internally by AdjustColors(FIBITMAP, Double, Double, Double, Boolean), which does not return the lookup table, but uses it to call AdjustCurve(FIBITMAP, Byte, FREE_IMAGE_COLOR_CHANNEL) on the passed image.

Reference