Added shaded renderer.

tilemapper/renderer.go

@@ -125,3 +125,51 @@ func (r *Renderer) CreateImage(colors []color.RGBA, background color.RGBA) *imag
 	}
 	return image
 }
+
+func safeColor(x int32) uint8 {
+	if x < 0 {
+		x = 0
+	} else if x > 255 {
+		x = 255
+	}
+	return uint8(x)
+}
+
+func (r *Renderer) CreateShadedImage(colors []color.RGBA, background color.RGBA) *image.RGBA {
+	pw, ph := r.width<<4, r.height<<4
+	image := image.NewRGBA(image.Rect(0, 0, pw, ph))
+	ofs, numCols := 0, int32(len(colors))
+	for z := ph - 1; z >= 0; z-- {
+		for x := 0; x < pw; x++ {
+			colIdx := r.cBuffer[ofs]
+			if colIdx < 0 || colIdx >= numCols {
+				image.Set(x, z, background)
+			} else {
+				var y, y1, y2 int32
+				y = r.yBuffer[ofs]
+				if x == 0 {
+					y1 = y
+				} else {
+					y1 = r.yBuffer[ofs-1]
+				}
+				if z == 0 {
+					y2 = y
+				} else {
+					y2 = r.yBuffer[ofs+pw]
+				}
+				d := ((y - y1) + (y - y2)) * 12
+				if d > 36 {
+					d = 36
+				}
+				col := colors[colIdx]
+				image.Set(x, z, color.RGBA{
+					R: safeColor(int32(col.R) + d),
+					G: safeColor(int32(col.G) + d),
+					B: safeColor(int32(col.B) + d),
+					A: 0xff})
+			}
+			ofs++
+		}
+	}
+	return image
+}