Initial data commit

Task/Xiaolin-Wus-line-algorithm/Wren/xiaolin-wus-line-algorithm.wren

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