In This Topic ▼

LBitmap::GammaCorrect

Summary

Adjusts the intensity of colors in the class object's bitmap by changing the gamma constant that is used to map the intensity values.

Syntax

#include "ltwrappr.h"

virtual L_INT LBitmap::GammaCorrect(uGamma, uFlags = 0)

Parameters

L_UINT 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.

L_UINT32 uFlags

Reserved for future use. Must be 0.

Returns

Value	Meaning
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 LBase::EnableStatusCallback.

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.

This function does not support 32-bit grayscale images. It returns the error code ERROR_GRAY32_UNSUPPORTED if a 32-bit grayscale image is passed to this function.

This function changes the color intensity of image data. If the image has a LUT, the function will work on the LUT, not the image data. If the image has a LUT and you want to work on the image data, set the UseLUT Flag in the BITMAPHANDLE structure to FALSE. Then, after calling the function, reset the UseLUT flag to TRUE as follows:

myBitmap.EnableUseLUT(FALSE); 
myBitmap.GammaCorrect(pBitmap,90, RGB_SPACE); 
myBitmap.EnableUseLUT(TRUE);

When applying contrast, gamma, and intensity changes to a bitmap, LEAD applies the changes in the following order:

Contrast
Intensity
Gamma

Gamma Correct Function - Before

Gamma Correct Function - After

View additional platform support for this Gamma Correct function.

Required DLLs and Libraries

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

Platforms

Win32, x64.

Example

L_INT LBitmap__GammaCorrectExample() 
{ 
   L_INT nRet; 
   LBitmap LeadBitmap; 
 
   nRet =LeadBitmap.Load(MAKE_IMAGE_PATH(TEXT("sample5.cmp")), 0,ORDER_BGR); 
   if(nRet !=SUCCESS) 
      return nRet; 
 
   nRet =LeadBitmap.GammaCorrect(235); 
   if(nRet !=SUCCESS) 
      return nRet; 
 
   return SUCCESS; 
}