Lesson 1: Bresenham’s Line Drawing Algorithm

  1.

void line(int x0, int y0, int x1, int y1, TGAImage &image, TGAColor color) {     for (float t=0.; t<1.; t+=.01) {         int x = x0*(1.-t) + x1*t;         int y = y0*(1.-t) + y1*t;         image.set(x, y, color);     } 
}
  2.
void line(int x0, int y0, int x1, int y1, TGAImage &image, TGAColor color) {     for (int x=x0; x<=x1; x++) {         float t = (x-x0)/(float)(x1-x0);         int y = y0*(1.-t) + y1*t;         image.set(x, y, color);     } }
3.
void line(int x0, int y0, int x1, int y1, TGAImage &image, TGAColor color) {     bool steep = false;     if (std::abs(x0-x1)<std::abs(y0-y1)) { // if the line is steep, we transpose the image         std::swap(x0, y0);         std::swap(x1, y1);         steep = true;     }     if (x0>x1) { // make it left−to−right         std::swap(x0, x1);         std::swap(y0, y1);     }     for (int x=x0; x<=x1; x++) {         float t = (x-x0)/(float)(x1-x0);         int y = y0*(1.-t) + y1*t;         if (steep) {             image.set(y, x, color); // if transposed, de−transpose         } else {             image.set(x, y, color);         }     } }
4.
void line(int x0, int y0, int x1, int y1, TGAImage &image, TGAColor color) {     bool steep = false;     if (std::abs(x0-x1)<std::abs(y0-y1)) {         std::swap(x0, y0);         std::swap(x1, y1);         steep = true;     }     if (x0>x1) {         std::swap(x0, x1);         std::swap(y0, y1);     }     int dx = x1-x0;     int dy = y1-y0;     float derror = std::abs(dy/float(dx));     float error = 0;     int y = y0;     for (int x=x0; x<=x1; x++) {         if (steep) {             image.set(y, x, color);         } else {             image.set(x, y, color);         }         error += derror;         if (error>.5) {             y += (y1>y0?1:-1);             error -= 1.;         }     } } 
5.
void line(int x0, int y0, int x1, int y1, TGAImage &image, TGAColor color) {     bool steep = false;     if (std::abs(x0-x1)<std::abs(y0-y1)) {         std::swap(x0, y0);         std::swap(x1, y1);         steep = true;     }     if (x0>x1) {         std::swap(x0, x1);         std::swap(y0, y1);     }     int dx = x1-x0;     int dy = y1-y0;     int derror2 = std::abs(dy)*2;     int error2 = 0;     int y = y0;     for (int x=x0; x<=x1; x++) {         if (steep) {             image.set(y, x, color);         } else {             image.set(x, y, color);         }         error2 += derror2;         if (error2 > dx) {             y += (y1>y0?1:-1);             error2 -= dx*2;         }     } }