91 lines
2.4 KiB
Text
91 lines
2.4 KiB
Text
import "graphics" for Canvas, Color
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import "dome" for Window
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import "math" for Math
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class XiaolinWu {
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construct new(width, height) {
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Window.title = "Xiaolin Wu's line algorithm"
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Window.resize(width, height)
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Canvas.resize(width, height)
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}
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init() {
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Canvas.cls(Color.white)
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drawLine(550, 170, 50, 435)
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}
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plot(x, y, c) {
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var col = Color.rgb(0, 0, 0, c * 255)
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x = ipart(x)
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y = ipart(y)
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Canvas.ellipsefill(x, y, x + 2, y + 2, col)
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}
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ipart(x) { x.truncate }
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fpart(x) { x.fraction }
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rfpart(x) { 1 - fpart(x) }
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drawLine(x0, y0, x1, y1) {
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var steep = Math.abs(y1 - y0) > Math.abs(x1 - x0)
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if (steep) drawLine(y0, x0, y1, x1)
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if (x0 > x1) drawLine(x1, y1, x0, y0)
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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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// handle first endpoint
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var xend = Math.round(x0)
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var yend = y0 + gradient * (xend - x0)
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var xgap = rfpart(x0 + 0.5)
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var xpxl1 = xend // this will be used in the main loop
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var ypxl1 = ipart(yend)
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if (steep) {
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plot(ypxl1, xpxl1, rfpart(yend) * xgap)
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plot(ypxl1 + 1, xpxl1, fpart(yend) * xgap)
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} else {
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plot(xpxl1, ypxl1, rfpart(yend) * xgap)
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plot(xpxl1, ypxl1 + 1, fpart(yend) * xgap)
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}
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// first y-intersection for the main loop
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var intery = yend + gradient
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// handle second endpoint
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xend = Math.round(x1)
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yend = y1 + gradient * (xend - x1)
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xgap = fpart(x1 + 0.5)
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var xpxl2 = xend // this will be used in the main loop
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var ypxl2 = ipart(yend)
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if (steep) {
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plot(ypxl2, xpxl2, rfpart(yend) * xgap)
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plot(ypxl2 + 1, xpxl2, fpart(yend) * xgap)
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} else {
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plot(xpxl2, ypxl2, rfpart(yend) * xgap)
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plot(xpxl2, ypxl2 + 1, fpart(yend) * xgap)
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}
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// main loop
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var x = xpxl1 + 1
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while (x <= xpxl2 - 1) {
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if (steep) {
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plot(ipart(intery), x, rfpart(intery))
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plot(ipart(intery) + 1, x, fpart(intery))
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} else {
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plot(x, ipart(intery), rfpart(intery))
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plot(x, ipart(intery) + 1, fpart(intery))
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}
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intery = intery + gradient
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x = x + 1
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}
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}
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update() {}
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draw(alpha) {}
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}
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var Game = XiaolinWu.new(640, 640)
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