all tasks

Task/Xiaolin-Wus-line-algorithm/Go/xiaolin-wus-line-algorithm-1.go

@@ -0,0 +1,79 @@
+package raster
+
+import "math"
+
+func ipart(x float64) float64 {
+    return math.Floor(x)
+}
+
+func round(x float64) float64 {
+    return ipart(x + .5)
+}
+
+func fpart(x float64) float64 {
+    return x - ipart(x)
+}
+
+func rfpart(x float64) float64 {
+    return 1 - fpart(x)
+}
+
+// AaLine plots anti-aliased line by Xiaolin Wu's line algorithm.
+func (g *Grmap) AaLine(x1, y1, x2, y2 float64) {
+    // straight translation of WP pseudocode
+    dx := x2 - x1
+    dy := y2 - y1
+    ax := dx
+    if ax < 0 {
+        ax = -ax
+    }
+    ay := dy
+    if ay < 0 {
+        ay = -ay
+    }
+    // plot function set here to handle the two cases of slope
+    var plot func(int, int, float64)
+    if ax < ay {
+        x1, y1 = y1, x1
+        x2, y2 = y2, x2
+        dx, dy = dy, dx
+        plot = func(x, y int, c float64) {
+            g.SetPx(y, x, uint16(c*math.MaxUint16))
+        }
+    } else {
+        plot = func(x, y int, c float64) {
+            g.SetPx(x, y, uint16(c*math.MaxUint16))
+        }
+    }
+    if x2 < x1 {
+        x1, x2 = x2, x1
+        y1, y2 = y2, y1
+    }
+    gradient := dy / dx
+
+    // handle first endpoint
+    xend := round(x1)
+    yend := y1 + gradient*(xend-x1)
+    xgap := rfpart(x1 + .5)
+    xpxl1 := int(xend) // this will be used in the main loop
+    ypxl1 := int(ipart(yend))
+    plot(xpxl1, ypxl1, rfpart(yend)*xgap)
+    plot(xpxl1, ypxl1+1, fpart(yend)*xgap)
+    intery := yend + gradient // first y-intersection for the main loop
+
+    // handle second endpoint
+    xend = round(x2)
+    yend = y2 + gradient*(xend-x2)
+    xgap = fpart(x2 + 0.5)
+    xpxl2 := int(xend) // this will be used in the main loop
+    ypxl2 := int(ipart(yend))
+    plot(xpxl2, ypxl2, rfpart(yend)*xgap)
+    plot(xpxl2, ypxl2+1, fpart(yend)*xgap)
+
+    // main loop
+    for x := xpxl1 + 1; x <= xpxl2-1; x++ {
+        plot(x, int(ipart(intery)), rfpart(intery))
+        plot(x, int(ipart(intery))+1, fpart(intery))
+        intery = intery + gradient
+    }
+}

Task/Xiaolin-Wus-line-algorithm/Go/xiaolin-wus-line-algorithm-2.go

@@ -0,0 +1,16 @@
+package main
+
+// Files required to build supporting package raster are found in:
+// * This task (immediately above)
+// * Bitmap
+// * Grayscale image
+// * Write a PPM file
+
+import "raster"
+
+func main() {
+    g := raster.NewGrmap(400, 300)
+    g.AaLine(7.4, 12.3, 307, 122.5)
+    g.AaLine(177.4, 12.3, 127, 222.5)
+    g.Bitmap().WritePpmFile("wu.ppm")
+}