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L_UnsharpMaskBitmap

Summary

Sharpens the specified image by applying the unsharp mask.

Syntax

#include "l_bitmap.h"

L_LTIMGEFX_API L_INT L_UnsharpMaskBitmap(pBitmap, nAmount, nRadius, nThreshold, uFlags)

Parameters

pBITMAPHANDLE pBitmap

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

L_INT nAmount

Value that represents an adjustment factor. This is a percentage.

L_INT nRadius

Value that indicates the size of the neighborhood used for blurring each pixel of the bitmap.

L_INT nThreshold

Value that indicates the threshold for modifying the original value of the pixel. If the difference in the original pixel value and the blurred pixel value is greater than the threshold value, the original pixel value will be modified. Possible values are:

0 to 65535 for 64-bit, 48-bit and 16-bit grayscale images.
0 to 4095 for 12-bit grayscale images.
0 to 255 otherwise.

L_UINT uFlags

Flag that indicates the color space in which to apply the mask. Possible values are:

Value	Meaning
RGB_SPACE	[0x0001] Apply the mask in the RGB color space.
YUV_SPACE	[0x0002] Apply the mask in the YUV color space.

Returns

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

Comments

This function is actually considered a sharpening function. It is used to sharpen the image with a minimum of noise. To reduce the noise, it starts by blurring a copy of the original image. The amount of blur depends on nRadius. The function then determines the difference between each pixel's value of the original image and the corresponding pixel's value in the blurred image. If the difference is greater than the nThreshold value, then the difference between the pixel values is multiplied by the value in the nAmount parameter and added to the original pixel value.

To increase the thickness of the sharpened edges, increase the value of nRadius.

To increase the amount of sharpness, increase the value of nAmount.

To reduce the noise and eliminate the small edges or individual pixels that will produce noise in image, increase the value of nThreshold.

Using the YUV color space decreases the processing time but some colors shift may happen.

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.

Unsharp Mask Function - Before

Unsharp Mask Function - After

View additional platform support for this Unsharp Mask function.

Required DLLs and Libraries

LTIMGEFX
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.

Example

This example loads a bitmap and increases its sharpness.
Load the bitmap, keeping the bits per pixel of the file

L_INT UnsharpMaskBitmapExample() 
{ 
   L_INT nRet; 
   BITMAPHANDLE LeadBitmap; 
 
   nRet = L_LoadBitmap(MAKE_IMAGE_PATH(TEXT("IMAGE1.CMP")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   nRet = L_UnsharpMaskBitmap(&LeadBitmap, 200, 15, 50, RGB_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; 
}