Linearizes the number of pixels, in a bitmap, based on the specified color space. This function is also useful for pre-processing images for the purpose of improving barcode recognition results.
#include "l_bitmap.h"
L_LTIMGCLR_API L_INT L_HistoEqualizeBitmap(pBitmap, uFlags)
Pointer to the bitmap handle referencing the bitmap to be changed.
Flag that indicates which color space to equalize. Possible values are:
Value | Meaning |
---|---|
RGB_SPACE | [0x0001] Linearizes the number of pixels across the RGB color space.(separated channels). |
YUV_SPACE | [0x0002] Linearizes the number of pixels across the YUV color space.(Best results). |
GRAY_SPACE | [0x0004] Linearizes the number of pixels per gray level in a gray level representation of the image. |
Value | Meaning |
---|---|
SUCCESS | The function was successful. |
< 1 | An error occurred. Refer to Return Codes. |
To update a status bar or detect a user interrupt during execution of this function, refer to L_SetStatusCallback.
Previously this function only equalized the number of pixels per gray level, using a gray level representation of the image. This functionality is now obtained by passing GRAY_SPACE for uFlags
.
For the best results, set uFlags to YUV_SPACE.
This function can process the whole image or a region of the image.
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.
Histogram Equalize Function - Before
Histogram Equalize Function - After
View additional platform support for this Histogram Equalize function.
Win32, x64, Linux.
For complete sample code, refer to the CHILD.C module of the DEMO example.
This example loads a bitmap and applies histogram equalization.
L_INT HistoEqualizeBitmapExample(L_VOID)
{
L_INT nRet;
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);
if (nRet != SUCCESS)
return nRet;
/* Histogram equalize the bitmap */
nRet = L_HistoEqualizeBitmap(&LeadBitmap, YUV_SPACE);
if (nRet != SUCCESS)
return nRet;
nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("Result.BMP")), &LeadBitmap, FILE_BMP, 24, 0, NULL);
if (nRet != SUCCESS)
return nRet;
//free bitmap
if (LeadBitmap.Flags.Allocated)
L_FreeBitmap(&LeadBitmap);
return SUCCESS;
}
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