(C++) AddColoredNoise

AddColoredNoise is a VCL graphics code snippet to add colored noise to a Extctrls::TImage.

The tool BarbaImage uses AddColoredNoise as one of its image operations.

View an image demonstrating 'AddColoredNoise' (png)


#include <cassert>

#include <cstdlib>

#include <Extctrls.hpp>



//Adds colored noise in range [0,max_rand>

// * max_rand = 0 denotes no noise added (image untouched)

// * max_rand = 255 denotes max noise added (image unrecognizable)

//From http://www.richelbilderbeek.nl/CppAddColoredNoise.htm

void AddColoredNoise (

  const Extctrls::TImage * const source,

  const int max_rand,

  Extctrls::TImage * const target)

{

  assert(max_rand >= 0);

  assert(max_rand < 256);

  assert(source!=0 && "Image is NULL");

  assert(source->Picture->Bitmap!=0 && "Image bitmap is NULL");

  assert(source->Picture->Bitmap->PixelFormat == pf24bit && "Image bitmap must be 24 bit");

  assert(target!=0 && "Image is NULL");

  assert(target->Picture->Bitmap!=0 && "Image bitmap is NULL");

  assert(target->Picture->Bitmap->PixelFormat == pf24bit && "Image bitmap must be 24 bit");

  //Get the width and height from the source

  const int width = source->Picture->Bitmap->Width;

  const int height = source->Picture->Bitmap->Height;

  //Set the target's width and height

  target->Picture->Bitmap->Width = width;

  target->Picture->Bitmap->Height = height;

  

  for (int y=0; y!=height; ++y)

  {

    const unsigned char * lineSource

      = static_cast<const unsigned char *>(

        source->Picture->Bitmap->ScanLine[y]);

    unsigned char * lineTarget

      = static_cast<unsigned char *>(

        target->Picture->Bitmap->ScanLine[y]);

    for (int x=0; x!=width; ++x)

    {

      const int rand = std::rand() % max_rand;

      const int blue = (static_cast<int>(lineSource[x*3+0]) + rand) % 256;

      const int green = (static_cast<int>(lineSource[x*3+1]) + rand) % 256;

      const int red = (static_cast<int>(lineSource[x*3+2]) + rand) % 256;

      assert(red >= 0);

      assert(red < 256);

      assert(green >= 0);

      assert(green < 256);

      assert(blue >= 0);

      assert(blue < 256);

      lineTarget[x*3+0]=blue; //Blue

      lineTarget[x*3+1]=green; //Green

      lineTarget[x*3+2]=red; //Red

    }

  }

}

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