59 lines
1.2 KiB
Plaintext
59 lines
1.2 KiB
Plaintext
func plot(x, y, c) {
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c && printf("plot %d %d %.1f\n", x, y, c);
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}
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func fpart(x) {
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x - int(x);
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}
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func rfpart(x) {
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1 - fpart(x);
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}
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func drawLine(x0, y0, x1, y1) {
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var p = plot;
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if (abs(y1 - y0) > abs(x1 - x0)) {
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p = {|arg| plot(arg[1, 0, 2]) };
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(x0, y0, x1, y1) = (y0, x0, y1, x1);
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}
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if (x0 > x1) {
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(x0, x1, y0, y1) = (x1, x0, y1, y0);
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}
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var dx = (x1 - x0);
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var dy = (y1 - y0);
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var gradient = (dy / dx);
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var xends = [];
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var intery;
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# handle the endpoints
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for x,y in [[x0, y0], [x1, y1]] {
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var xend = int(x + 0.5);
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var yend = (y + gradient*(xend-x));
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var xgap = rfpart(x + 0.5);
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var x_pixel = xend;
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var y_pixel = yend.int;
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xends << x_pixel;
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p.call(x_pixel, y_pixel , rfpart(yend) * xgap);
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p.call(x_pixel, y_pixel+1, fpart(yend) * xgap);
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defined(intery) && next;
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# first y-intersection for the main loop
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intery = (yend + gradient);
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}
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# main loop
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range(xends[0]+1, xends[1]-1).each { |x|
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p.call(x, intery.int, rfpart(intery));
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p.call(x, intery.int+1, fpart(intery));
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intery += gradient;
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}
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}
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drawLine(0, 1, 10, 2);
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