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(C++) ConvertToGrey

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

* View the code of 'ConvertToGrey' in plain text

//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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