From f39b2eb216ffca60d62e20c3369b755eb68e8567 Mon Sep 17 00:00:00 2001
From: Mendel E <mendelmaleh@gmail.com>
Date: Thu, 7 May 2020 17:14:30 -0400
Subject: [PATCH] Rework diagonal drawing

Fix rectangles too.
---
 image.go   | 27 ++++++++++++++-------------
 options.go |  3 ---
 2 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/image.go b/image.go
index bb39957..b5f9b46 100644
--- a/image.go
+++ b/image.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}
 }
diff --git a/options.go b/options.go
index 117673d..49955c2 100644
--- a/options.go
+++ b/options.go
@@ -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
 }
-- 
2.38.5