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LBitmap::ColorLevel

Summary

Applies color leveling to an image. It changes the image shadows, midtones and highlights.

Syntax

#include "ltwrappr.h"

virtual L_INT LBitmap::ColorLevel (pLvlClr, uFlags)

Parameters

pLVLCLR 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.

L_UINT 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

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

Comments

This function is also useful for pre-processing images for the purpose of improving barcode recognition results.

Before calling the LBitmap::ColorLevel function, initialize the size and all remaining fields of the LVLCLRINF structures within the LVLCLR structure. These fields tell LBitmap::ColorLevel 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 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.

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.

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

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.

Color Level Function - Before

Color Level Function - After

View additional platform support for this Color Level 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.

Example

This example applies image leveling to an image.

L_INT LBitmap__ColorLevelExample(LAnimationWindow * LAniWnd)  
{ 
   LVLCLR lvlClr;  
    
   lvlClr.uStructSize = sizeof(LVLCLR);  
   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 */ 
   return LAniWnd->ColorLevel (&lvlClr, LEVEL_BLUE | LEVEL_MASTER);  
 
}