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L_AddShadowBitmap

Summary

Adds shadows to the bitmap.

Syntax

#include "l_bitmap.h"

L_LTIMGSFX_API L_INT L_AddShadowBitmap(pBitmap, uAngle, uThreshold, uFlags)

Parameters

pBITMAPHANDLE pBitmap

Pointer to the bitmap handle that references the bitmap on which to apply the effect.

L_UINT uAngle

Angle value indicating the direction of the light source producing the shadow. Possible values are:

Value	Meaning
SHADOW_E	[0] East
SHADOW_NE	[1] Northeast
SHADOW_N	[2] North
SHADOW_NW	[3] Northwest
SHADOW_W	[4] West
SHADOW_SW	[5] Southwest
SHADOW_S	[6] South
SHADOW_SE	[7] Southeast

L_UINT uThreshold

Threshold value used to determine which pixels will be affected . Valid values range from 0 through 65535 for 64-bit, 48-bit and 16-bit grayscale images and from 0 through 4095 for 12-bit grayscale images. Otherwise, it is from 0 through 255. When uFlags = COLOR_RGB, any component (R, G, or B) of a pixel with a value less than the uThreshold value is not affected. When uFlags = COLOR_GRAY, any pixel where the master channel value is less than the uThreshold value is not affected.

L_UINT uFlags

Type of the shadow. Possible values are:

Value	Meaning
SHADOW_CLR_RGB	[0] Shadows are colored.
SHADOW_CLR_GRAY	[1] Shadows are grayscale.

Returns

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

Comments

This function applies a convolution matrix upon each color component and then combines the results in order to add shadows.

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 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.

To update a status bar or detect a user interrupt during execution of this function, refer to L_SetStatusCallback.

Calculating Master Channel Values

In order to speed up widely used image processing filters in LEADTOOLS, the grayscale value (master channel) of a colored image is calculated using the following formulas:

#define CalcGrayValue(r, g, b) ((L_UCHAR)(((L_UCHAR) (((2 * (L_UINT) (r)) + (5 * (L_UINT) (g)) + (L_UINT) (b) + 4) / 8)))) 
#define CalcGrayValue16(r, g, b) ((L_UINT16) (((2 * (L_UINT32) (r)) + (5 * (L_UINT32) (g)) + (L_UINT32) (b) + 4) / 8)) 
#define CalcGrayValue32(r, g, b) ((L_UINT32) (((2 * (L_UINT32) (r)) + (5 * (L_UINT32) (g)) + (L_UINT32) (b) + 4) / 8))

Shadow Function - Before

Shadow Function - After

View additional platform support for this Shadow function.

Required DLLs and Libraries

LTIMGSFX
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

L_INT AddShadowBitmapExample(L_VOID) 
{ 
   L_INT nRet; 
   BITMAPHANDLE LeadBitmap;   /* Bitmap handle for the image */ 
 
   /* Load a bitmap at its own bits per pixel  */ 
   nRet = L_LoadBitmap(MAKE_IMAGE_PATH(TEXT("Master.jpg")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   /* Apply  shadow effect  to the image*/ 
   nRet = L_AddShadowBitmap(&LeadBitmap, SHADOW_SE, 0, SHADOW_CLR_GRAY); 
   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; 
}