L_GammaCorrectBitmap

#include "l_bitmap.h"

L_INT EXT_FUNCTION L_GammaCorrectBitmap(pBitmap, uGamma)

pBITMAPHANDLE pBitmap;	/* pointer to the bitmap handle */
L_UINT uGamma;	/* unsigned integer that represents the gamma value */

Adjusts the intensity of colors in a bitmap by changing the gamma constant that is used to map the intensity values.

Parameter	Description
pBitmap	Pointer to the bitmap handle referencing the bitmap to change.
uGamma	Unsigned integer that represents the gamma value. It can be any number greater than 0.
	Because this is an unsigned integer, it is 100 times the actual gamma value. For example, use 235 to set a gamma value of 2.35.

Returns

SUCCESS	The function was successful.
< 1	An error occurred. Refer to Return Codes.

Comments

Intensity values ideally follow a logarithmic progression, because the eye perceives changes in intensity as being equal when the ratio of change is equal. For example, we would see a change from 0.1 to 0.2 as being equal to a change from 0.2 to 0.4.

Gamma is a standard constant that is used to calculate the progression. For most CRTs the gamma constant is in the range of 2.2 to 2.5.

To update a status bar or detect a user interrupt during execution of this function, refer to L_SetStatusCallback.

This function supports 12 and 16-bit grayscale and 48 and 64-bit color images. Support for 12 and 16-bit grayscale and 48 and 64-bit color images is available only in the Document/Medical toolkits.

Required DLLs and Libraries

LTIMG

For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

See Also

Functions:	L_ChangeBitmapIntensity, L_ChangeBitmapContrast, L_HistoContrastBitmap, L_StretchBitmapIntensity, L_RemapBitmapIntensity, L_InvertBitmap, L_ChangeBitmapHue, L_ChangeBitmapSaturation, L_HistoEqualizeBitmap, L_FillBitmap, L_GetPixelColor, L_PutPixelColor, L_GetBitmapHistogram, L_DlgGammaAdjustment, L_WindowLevel, L_ChannelMix, L_DeinterlaceBitmap, L_DesaturateBitmap, L_EdgeDetectStatisticalBitmap, L_LightControlBitmap, L_SmoothEdgesBitmap, L_LocalHistoEqualizeBitmap, L_AddWeightedBitmaps, L_ColorMergeBitmap, L_ColorSeparateBitmap, L_ConvertColorSpace, L_MultiplyBitmap, L_AutoColorLevelBitmap, L_ColorLevelBitmap, L_CorrelationBitmap, L_GrayScaleToDuotone, L_GrayScaleToMultitone, L_HolesRemovalBitmapRgn, L_SelectiveColorBitmap, L_SkeletonBitmap, L_ChangeHueSatIntBitmap, L_ColorReplaceBitmap, L_ColorThresholdBitmap, L_MathFunctionBitmap, L_SegmentBitmap, L_AdaptiveContrastBitmap, L_ApplyMathLogicBitmap, L_ColorIntensityBalance, L_ColorizeGrayBitmap, L_ContBrightIntBitmap, L_DigitalSubtractBitmap, L_DynamicBinaryBitmap, L_EdgeDetectEffectBitmap, L_FunctionalLightBitmap, L_MultiScaleEnhancementBitmap, L_SelectBitmapData, L_ShiftBitmapData, L_AdjustBitmapTint, L_GammaCorrectBitmapExt
Topics:	Raster Image Functions: Modifying Intensity Values
	Changing Brightness and Contrast
	Raster Image Functions: Changing Brightness and Contrast

Example

For complete sample code, refer to the CHILD.C module of the DEMO example.

/* This example loads a bitmap and applies gamma correction. */
BITMAPHANDLE LeadBitmap; /* Bitmap handle to hold the loaded image. */
/* Load the bitmap, keeping the bits per pixel of the file */
L_LoadBitmap (TEXT("IMAGE1.CMP"), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL);
/* Set a gamma value of 2.5 */
L_GammaCorrectBitmap(&LeadBitmap, 250 );