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(C++) DrawGlobe

Graphics code snippet to draw a globe

* View an example image of a globe created by DrawGlobe.

* View the code of 'DrawGlobe' for VCL in plain text.

CLX

Under construction.

VCL

#include <cassert> //For assert

#include <cmath> //For std::sqrt

#include <algorithm> //For std::min

//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;

}

}

}

}

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