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LOLWUT: draw lines using Bresenham algorithm.

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This commit is contained in:
antirez 2018-09-11 21:15:43 +02:00
parent 7777379814
commit a974531d1a
1 changed files with 26 additions and 2 deletions
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28
src/lolwut.c
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@ -88,7 +88,7 @@ void lwFreeCanvas(lwCanvas *canvas) {
* dot will be displyed, and 1 means dot will be displayed.
* Coordinates are arranged so that left-top corner is 0,0. You can write
* out of the size of the canvas without issues. */
void lwPutPixel(lwCanvas *canvas, int x, int y, int color) {
void lwDrawPixel(lwCanvas *canvas, int x, int y, int color) {
if (x < 0 || x >= canvas->width ||
y < 0 || y >= canvas->height) return;
canvas->pixels[x+y*canvas->width] = color;
@ -101,6 +101,29 @@ int lwGetPixel(lwCanvas *canvas, int x, int y) {
return canvas->pixels[x+y*canvas->width];
}
/* Draw a line from x1,y1 to x2,y2 using the Bresenham algorithm. */
void lwDrawLine(lwCanvas *canvas, int x1, int y1, int x2, int y2, int color) {
int dx = abs(x2-x1);
int dy = abs(y2-y1);
int sx = (x1 < x2) ? 1 : -1;
int sy = (y1 < y2) ? 1 : -1;
int err = dx-dy, e2;
while(1) {
lwDrawPixel(canvas,x1,y1,color);
if (x1 == x2 && y1 == y2) break;
e2 = err*2;
if (e2 > -dy) {
err -= dy;
x1 += sx;
}
if (e2 < dx) {
err += dx;
y1 += sy;
}
}
}
/* Converts the canvas to an SDS string representing the UTF8 characters to
* print to the terminal in order to obtain a graphical representaiton of the
* logical canvas. The actual returned string will require a terminal that is
@ -133,8 +156,9 @@ sds lwRenderCanvas(lwCanvas *canvas) {
int main(void) {
lwCanvas *c = lwCreateCanvas(80,80);
for (int i = 0; i < 40; i++) {
lwPutPixel(c,i,i,1);
lwDrawPixel(c,i,i,1);
}
lwDrawLine(c,10,10,60,30,1);
sds rendered = lwRenderCanvas(c);
printf("%s\n", rendered);
}