ConvertToGrey is a graphics code snippet to convert a color VCL TImage to a grey TImage.

In the 'ConvertToGrey' example image you see an original color image, this image converted to grey and the result of a histogram equalization on the grey image.

View an example of an image converted to grey (png)


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

void ConvertToGrey(const TImage * const source, TImage * const target)

{

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

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

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

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

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

  assert(target->Picture->Bitmap->PixelFormat == pf24bit && "Target 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 grey

        = (lineSource[x*3+0] + lineSource[x*3+1] + lineSource[x*3+2]) / 3;



      lineTarget[x*3+0]=grey; //Blue

      lineTarget[x*3+1]=grey; //Green

      lineTarget[x*3+2]=grey; //Red

    }

  }

}

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(C++) ConvertToGrey