(C++) DrawGlobe

 

DrawGlobe is a graphics code snippet to draw a globe.

 

• View an example of 'DrawGlobe' (png)

 

 

 

 

 

DrawGlobe using the Qt library

 

• Download the Qt Creator project 'CppDrawGlobe' (zip)
• View the Qt Creator source code of 'CppDrawGlobe' as a web page (htm)

 

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//From http://www.richelbilderbeek.nl/CppDrawGlobe.htm QPixmap DrawGlobe(   const int width,   const int height,   const unsigned char r,   const unsigned char g,   const unsigned char b) {   QPixmap pixmap(width,height);   QImage image = pixmap.toImage();   assert(image.bytesPerLine() / width == 4     && "Assume there are 4 bytes per pixel");   const double r_max = boost::numeric_cast<double>(r);   const double g_max = boost::numeric_cast<double>(g);   const double b_max = boost::numeric_cast<double>(b);   const double midX = boost::numeric_cast<double>(width ) / 2.0;   const double midY = boost::numeric_cast<double>(height) / 2.0;   const double max_dist = std::min(midX,midY);   for (int y=0; y!=height; ++y)   {     unsigned char * const line       = static_cast<unsigned char *>(image.scanLine(y));     const double y_d = boost::numeric_cast<double>(y);     for (int x=0; x!=width; ++x)     {       const double x_d = boost::numeric_cast<double>(x);       const double dist         = std::sqrt(             ((x_d - midX) * (x_d - midX))           + ((y_d - midY) * (y_d - midY)) );       if (dist <= max_dist)       {         const double rel_dist = dist / max_dist;         const int r_here = rel_dist * r_max;         const int g_here = rel_dist * g_max;         const int b_here = rel_dist * b_max;         assert( r_here >= 0);         assert( r_here < 256);         assert( g_here >= 0);         assert( g_here < 256);         assert( b_here >= 0);         assert( b_here < 256);         line[x*4+3] = 255; //Alpha value         line[x*4+2] = r_here; //Red         line[x*4+1] = g_here; //Green         line[x*4+0] = b_here; //Blue       }       else       {         line[x*4+3] = 0; //Alpha value         line[x*4+2] = 0; //Red         line[x*4+1] = 0; //Green         line[x*4+0] = 0; //Blue       }     }   }   pixmap = pixmap.fromImage(image);   //Add transparency   const QBitmap mask = pixmap.createMaskFromColor(QColor(0,0,0,0).rgb());   pixmap.setMask(mask);   return pixmap; }

 

 

 

 

 

DrawGlobe using the VCL library

 

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#include <algorithm> //For std::min #include <cassert>   //For assert #include <cmath>     //For std::sqrt //From http://www.richelbilderbeek.nl/CppDrawGlobe.htm void DrawGlobe(   TImage * const image,   const unsigned char rMax,   const unsigned char gMax,   const unsigned char bMax) {   assert(image!=0);   const int width  = image->Picture->Bitmap->Width;   const int height = image->Picture->Bitmap->Height;   const double midX = static_cast<double>(width ) / 2.0;   const double midY = static_cast<double>(height) / 2.0;   const double maxDist = std::min(midX,midY);   for (int y=0; y!=height; ++y)   {     unsigned char * const line       = static_cast<unsigned char *>(image->Picture->Bitmap->ScanLine[y]);     const double yD = static_cast<double>(y);     for (int x=0; x!=width; ++x)     {       const double xD = static_cast<double>(x);       const double dist = std::sqrt( ((xD - midX) * (xD - midX)) + ((yD - midY) * (yD - midY)) );       if (dist <= maxDist)       {         const double relDist = dist / maxDist;         const int r = relDist * static_cast<double>(rMax);         const int g = relDist * static_cast<double>(gMax);         const int b = relDist * static_cast<double>(bMax);         assert( r >= 0);         assert( r < 256);         assert( g >= 0);         assert( g < 256);         assert( b >= 0);         assert( b < 256);         line[x*3+2] = (r == 0 ? 1 : r); //Never use a zero for red         line[x*3+1] = (g == 0 ? 1 : g); //Never use a zero for green         line[x*3+0] = (b == 0 ? 1 : b); //Never use a zero for blue       }       else       {         line[x*3+2] = 0;         line[x*3+1] = 0;         line[x*3+0] = 0;       }     }   } }