L_AutoColorLevelBitmap

#include "l_bitmap.h"

L_LTIMGCLR_API L_INT L_AutoColorLevelBitmap(pBitmap, pLvlClr, uBlackClip, uWhiteClip, uFlags)

Applies one of several types of automatic color leveling to an image. This function is also useful for pre-processing images for the purpose of improving barcode recognition results.

Returns

Comments

This function does not support signed data images. It returns the error code ERROR_SIGNED_DATA_NOT_SUPPORTED if a signed data image is passed to this function.

This function makes the dark values darker and the light values lighter, which automatically enhances shadows and brightens the image. It also maximizes the tonal range of the image. It enhances the contrast and intensity using the image's histogram and a color distribution-based algorithm.

Before you call L_AutoColorLevelBitmap, you need to initialize the size of the LVLCLR structure. The other fields in the structure will be updated with the uMinInput, uMaxInput, uMinOutput, uMaxOutput and uGamma values used by the function for the appropriate channel(s).

If you set the AUTO_NOPROCESS flag in uFlags, the pLvlClr parameter will be updated with the color leveling information used by the L_AutoColorLevelBitmap function. If you then pass the updated pLvlClr structure to the L_ColorLevelBitmap function, you will obtain the same result that you would have obtained if you had called the L_AutoColorLevelBitmap function with the leveling flag by itself.

If you set AUTO_NOPROCESS in uFlags and pass NULL to pLvlClr the function will return an error code.

If you pass only AUTO_NOPROCESS to uFlags then the function will return an error code.

If the image is a grayscale image, then AUTO_LEVEL, AUTO_CONTRAST and AUTO_INTENSITY give identical results. Also the member variables master, red, green and blue of the structure pLvlClr will have the same values.

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.

If the bitmap has a region, the effect will be applied on the region only.

For an example, click here

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.

Required DLLs and Libraries

Platforms

Win32, x64, Mobile.

See Also

Example

This example loads a bitmap and applies auto image leveling.

 L_INT AutoColorLevelBitmapExample(L_VOID)
{
   L_INT nRet;
   BITMAPHANDLE LeadBitmap;   /* Bitmap handle to hold the loaded image. */
   LVLCLR lc;        /* Structure to hold the level values, used for display only */
   L_TCHAR buffer[100];


   /* 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;

   /* Apply "Auto Leveling" to the bitmap */
   lc.uStructSize = sizeof(LVLCLR);
   nRet = L_AutoColorLevelBitmap (&LeadBitmap, &lc, DEFAULT_BLACK_CLIP, DEFAULT_WHITE_CLIP, AUTO_LEVEL);
   if(nRet !=SUCCESS)
      return nRet;
   wsprintf (buffer, TEXT("Min and Max input values for the blue channel using auto level are %d and %d"), lc.blue.nMinInput, lc.blue.nMaxInput);
   if(LeadBitmap.Flags.Allocated)  
      L_FreeBitmap(&LeadBitmap);  

   return SUCCESS;
}