wu algo

util/wu/line.go

@@ -0,0 +1,78 @@
+package wu
+
+import (
+	"lab.zaar.be/thefish/alchemyst-go/engine/types"
+	"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)
+}
+
+func (Layer types.Putable) WuLine(x1, y1, x2, y2 float64, w int) {
+	dx := x2 - x1
+	dy := y2 - y1
+	ax := dx
+	if ax < 0 {
+		ax = -ax
+	}
+	ay := dy
+	if ay < 0 {
+		ay = -ay
+	}
+
+	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) {
+			Layer.Put(y, x,  uint8(255 * c))
+		}
+	} else {
+		plot = func(x, y int, c float64) {
+			Layer.Put(x, y, uint8(255 * c))
+		}
+	}
+	if x2 < x1 {
+		x1, x2 = x2, x1
+		y1, y2 = y2, y1
+	}
+	gradient := dy / dx
+
+	xend := round(x1)
+	yend := y1 + gradient*(xend-x1)
+	xgap := rfpart(x1 + .5)
+	xpxl1 := int(xend)
+	ypxl1 := int(ipart(yend))
+	plot(xpxl1, ypxl1, rfpart(yend)*xgap)
+	plot(xpxl1, ypxl1+1, fpart(yend)*xgap)
+	intery := yend + gradient
+
+	xend = round(x2)
+	yend = y2 + gradient*(xend-x2)
+	xgap = fpart(x2 + 0.5)
+	xpxl2 := int(xend)
+	ypxl2 := int(ipart(yend))
+	plot(xpxl2, ypxl2, rfpart(yend)*xgap)
+	plot(xpxl2, ypxl2+1, fpart(yend)*xgap)
+
+	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
+	}
+}