L_LTIMGCLR_API L_INT L_HistoContrastBitmap(pBitmap, nChange, uFlags)
Increases or decreases the contrast of the image in a bitmap, using a histogram to determine the median brightness.
Pointer to the bitmap handle referencing the bitmap to be modified.
Amount of contrast change. Valid values are -1000 to +1000.
Reserved for future use. Must be 0.
|SUCCESS||The function was successful.|
|< 1||An error occurred. Refer to Return Codes.|
This function finds the median brightness of the image; then brightens the pixels with values above the median and darkens the pixels with values below the median. This is more sophisticated (but slower) than the L_ChangeBitmapContrast function, which uses the middle possible value (128) rather than finding the actual median.
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 in the Document and Medical Imaging 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 adjusts the contrast histogram of the 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:
pBitmap->Flags.UseLUT = FALSE;
L_HistoContrastBitmap(pBitmap, 250, 0);
pBitmap->Flags.UseLUT = TRUE;
Required DLLs and Libraries
Win32, x64, Linux.
This example loads a bitmap and increases its contrast.
BITMAPHANDLE LeadBitmap; /* Bitmap handle to hold the loaded image. */
/* Load the bitmap, keeping the bits per pixel of the file */
nRet = L_LoadBitmap (MAKE_IMAGE_PATH(TEXT("IMAGE1.CMP")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL);
/* Increase the contrast using the histogram by 25 percent of the possible range */
nRet = L_HistoContrastBitmap(&LeadBitmap, 250 , 0);
nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("Result.BMP")), &LeadBitmap, FILE_BMP, 24, 0, NULL);
Medical Web Viewer .NET
.NET, Java, Android, and iOS/macOS Assemblies
C API/C++ Class Libraries