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L_AddBitmapNoise

Summary

Adds random pixels to a bitmap, letting you specify the percentage of coverage and the color plane.

Syntax

#include "l_bitmap.h"

L_LTIMGEFX_API L_INT L_AddBitmapNoise(pBitmap, uRange, uChannel, uFlags)

Parameters

pBITMAPHANDLE pBitmap

Pointer to the bitmap handle referencing the bitmap to process.

L_UINT uRange

Percentage of coverage, expressed in tenths of a percent. Valid values are 0 to 1000.

L_UINT uChannel

Possible values are:

Value	Meaning
CHANNEL_MASTER *	[0] All channels.
CHANNEL_RED	[1] Red channel only.
CHANNEL_GREEN	[2] Green channel only.
CHANNEL_BLUE	[3] Blue channel only.

Returns

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

Comments

Use this function in order to add random noise to a bitmap.

Use the L_PerlinBitmap function to use a pseudo-random number generator in order to create a Perlin noise, and then procedurally transform that noise into a texture. Depending on the flags that are set, the texture can be saved as a bitmap by itself, or the texture can be combined with another bitmap. For more information, refer to Using the L_PerlinBitmap function.

Use the L_CloudsBitmap function in order to use Perlin equations to generate pseudo-random noise, and then procedurally transform that noise into a cloud-like texture. The L_CloudsBitmap function applies equations to the Perlin noise that are different than those used by the L_PerlinBitmap function.

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.

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 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.

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))

Add Noise Function - Before

Add Noise Function - After

View additional platform support for this Add Noise 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

For complete sample code, refer to the CHILD.C module of the DEMO example.
This example loads a bitmap and adds red noise to it.

L_INT AddBitmapNoiseExample(L_VOID) 
{ 
   L_INT nRet; 
   BITMAPHANDLE LeadBitmap;   /* Bitmap handle to hold the loaded image. */ 
 
   /* Load the bitmap, keeping the bits per pixel of the file */ 
   nRet = L_LoadBitmap(MAKE_IMAGE_PATH(TEXT("sample2.cmp")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   /* Add red noise with 25 percent coverage */ 
   nRet = L_AddBitmapNoise(&LeadBitmap, 250, CHANNEL_RED, 0); 
   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; 
}