(C++) Darken

 

Darken is a Graphics code snippet to darken a Extctrls::TImage. To bleach a Extctrls::TImage use Bleach.

 

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

 

• View an example of a composition image demonstrating 'Darken'

 

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#include <cassert> #include <Extctrls.hpp> //Darken an image by fraction f // * f = 0.0 denotes no bleaching  (image untouched) // * f = 1.0 denotes max bleaching (image black) //From http://www.richelbilderbeek.nl/CppDarken.htm void Darken(   const Extctrls::TImage * const source,   const double f,                     Extctrls::TImage * const target) {   assert(f >=  0.0);   assert(f <=  1.0);   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 r = lineSource[x*3+2]; //Red;       const int g = lineSource[x*3+1]; //Green;       const int b = lineSource[x*3+0]; //Blue;       const double dist_r = static_cast<double>(r) * (1.0-f);       const double dist_g = static_cast<double>(g) * (1.0-f);       const double dist_b = static_cast<double>(b) * (1.0-f);       const int new_r = static_cast<int>(dist_r);       const int new_g = static_cast<int>(dist_g);       const int new_b = static_cast<int>(dist_b);       assert(new_r >=   0);       assert(new_r <  256);       assert(new_g >=   0);       assert(new_g <  256);       assert(new_b >=   0);       assert(new_b <  256);       lineTarget[x*3+2] = new_r; //Red       lineTarget[x*3+1] = new_g; //Green       lineTarget[x*3+0] = new_b; //Blue     }   } }