2 files changed, 14 insertions(+), 16 deletions(-)

M image.go
M options.go

@@ 17,23 17,24 @@ func Image(opt Options) image.Image {
 	case "plain":
 		draw.Draw(im, im.Bounds(), image.NewUniform(opt.Colors[0]), image.Point{}, draw.Src)
 	case "diagonal":
-		var c [2]color.RGBA
-		copy(c[:], opt.Colors)
-		im.drawDiagonal(opt.Width, opt.Height, c)
+		h, w := float64(im.Bounds().Max.Y-im.Bounds().Min.Y), float64(im.Bounds().Max.X-im.Bounds().Min.X)
+
+		draw.Draw(im, im.Bounds(), image.NewUniform(opt.Colors[0]), image.Point{}, draw.Src)
+		draw.DrawMask(im, im.Bounds(), image.NewUniform(opt.Colors[1]), image.Point{}, &diagonal{im, h, w}, image.Point{}, draw.Over)
 	}
 
 	return im
 }
 
-func (im *img) drawDiagonal(w, h int, c [2]color.RGBA) {
-	for x := 0; x < w; x++ {
-		for y := 0; y < h; y++ {
-			// if y < h/w)*x) {
-			if y <= h-x {
-				im.Set(x, y, c[0])
-			} else {
-				im.Set(x, y, c[1])
-			}
-		}
+type diagonal struct {
+	image.Image
+	h, w float64
+}
+
+func (im *diagonal) At(x, y int) color.Color {
+	if float64(y)+0.5 < im.h-(im.h/im.w)*float64(x) {
+		return color.Alpha{}
 	}
+
+	return color.Alpha{0xff}
 }

@@ 94,7 94,4 @@ func (opt *Options) Normalize() {
 	if opt.Width > 600 {
 		opt.Width = 600
 	}
-
-	// TODO: fix rectangles, for now only squares
-	opt.Height = opt.Width
 }