L_ColorLevelBitmap

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#include "l_bitmap.h"

L_LTIMGCLR_API L_INT L_ColorLevelBitmap(pBitmap, pLvlClr, uFlags)

pBITMAPHANDLE pBitmap;	/* pointer to the bitmap handle */
pLVLCLR pLvlClr;	/* pointer to a LVLCLR structure */
L_UINT uFlags;	/* a flag that indicates the channel being color leveled */

Applies color leveling to an image. It changes the image shadows, midtones and highlights. This function is also useful for pre-processing images for the purpose of improving barcode recognition results.

Parameter	Description
pBitmap	Pointer to the bitmap handle.
pLvlClr	Pointer to a LVLCLR structure that contains several LVLCLRINF structures, which in turn contain information on the shadows, midtones and highlights for the Red, Green, Blue and Master channels.
uFlags	Flag that indicates the channel being leveled. Possible values are:
	Value	Meaning
	LEVEL_RED	[0x0001] Red channel
	LEVEL_GREEN	[0x0010] Green channel
	LEVEL_BLUE	[0x0100] Blue channel
	LEVEL_MASTER	[0x1000] All channels

Returns

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

Comments

Before you call the L_ColorLevelBitmap function, you need to initialize the size and all remaining fields of the LVLCLRINF structures within the LVLCLR structure. These fields tell L_ColorLevelBitmap what constitutes shadows, midtones, and highlights and how to remap the shadows, midtones and highlights.

Control the amount of image balance and leveling by controlling the values of the nMinInput, nMaxInput, nMinOutput, nMaxOutput, and uGamma members of the LVLCLRINF structure contained in the pLvlClr parameter.

The nMinInput member of an LVLCLRINF structure defines what the function interprets as shadows for that color channel. Any value less than or equal to nMinInput is considered a shadow.
The nMaxInput member of an LVLCLRINF structure defines what the function interprets as highlights for that color channel. Any value greater than or equal to nMaxInput is considered a highlight.
The value of the nMaxInput member must be greater than the value of the nMinInput member by at least 2.
Midtones are those values between nMinInput and nMaxInput.
The nMinOutput member is the value to which the shadows will be mapped.
The nMaxOutput member is the value to which the highlights will be mapped.
The uGamma member is used to modify the midtone values

If only LEVEL_MASTER is set in uFlags then the rest of the channels will still be affected.

If the image is a grayscale image, then you must set LEVEL_MASTER in uFlags, otherwise the function will not have any effect.

If nMinOutput > nMaxOutput then the bitmaps shadows and highlights will be inverted.

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

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

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, Linux.

See Also

Functions:	L_SharpenBitmap, L_PosterizeBitmap, L_MosaicBitmap, L_EmbossBitmap, L_MedianFilterBitmap, L_AddBitmapNoise, L_IntensityDetectBitmap, L_SpatialFilterBitmap, L_BinaryFilterBitmap, L_MaxFilterBitmap, L_MinFilterBitmap, L_OilifyBitmap, L_SolarizeBitmap, L_DlgColor, L_WindowLevel, L_AutoColorLevelBitmap, L_SelectiveColorBitmap, L_AdjustBitmapTint, L_ColorHalfToneBitmap, L_AutoBinarizeBitmap, L_DynamicBinaryBitmap, L_AutoBinaryBitmap
Topics:	Raster Image Functions: Modifying Intensity Values
	Changing Brightness and Contrast
	Raster Image Functions: Changing Brightness and Contrast
	Correcting Colors
	Color Halftone and Halftone Images
	Raster Image Functions: Correcting Colors

Example

For complete sample code, refer to the CHILD.C module of the DEMO example. This example loads a bitmap and applies image leveling to it.

#define MAKE_IMAGE_PATH(pFileName) TEXT("C:\\Users\\Public\\Documents\\LEADTOOLS Images\\")pFileName


 L_INT ColorLevelBitmapExample(L_VOID)
{
   L_INT nRet;
   BITMAPHANDLE LeadBitmap;   /* Bitmap handle to hold the loaded image. */
   LVLCLR lvlClr; 

   /* 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;

   lvlClr.uStructSize = sizeof(LVLCLR);
   /* Specify Image levels */
   lvlClr.blue.nMinInput = 20;
   lvlClr.blue.nMaxInput = 200;
   lvlClr.blue.nMinOutput = 0;
   lvlClr.blue.nMaxOutput = 255;
   lvlClr.blue.uGamma = DEFAULT_GAMMA;

   // Master will cause the image to be Inversed
   lvlClr.master.nMinInput = 0;
   lvlClr.master.nMaxInput = 255;
   lvlClr.master.nMinOutput = 255;
   lvlClr.master.nMaxOutput = 0;
   lvlClr.master.uGamma = DEFAULT_GAMMA;

   /* Level the Blue and Master channels */
   nRet = L_ColorLevelBitmap (&LeadBitmap, &lvlClr, LEVEL_BLUE | LEVEL_MASTER);
   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;
}