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;
}
}
}