From cbe14d53cda6524c1d33b2e22a4539db80d452e7 Mon Sep 17 00:00:00 2001
From: David Ashby <delta.mu.alpha@gmail.com>
Date: Mon, 11 Jan 2021 19:54:03 -0500
Subject: [PATCH] wrap all that repetition in a closure

---
 quantizer.go | 58 +++++++++++++++-------------------------------------
 1 file changed, 16 insertions(+), 42 deletions(-)

diff --git a/quantizer.go b/quantizer.go
index 4d84e0d..248b999 100644
--- a/quantizer.go
+++ b/quantizer.go
@@ -134,15 +134,7 @@ func applyError(diffusion diffusion, quantError float64, currentPixel coord, err
 	}
 }
 
-func simpleErrorDiffusion() quantizerFunction {
-	errMap := make(map[coord]float64)
-	d := diffusion{
-		divisor: 2.0,
-		matrix: map[coord]float64{
-			{x: 1, y: 0}: 1.0,
-			{x: 0, y: 1}: 1.0,
-		},
-	}
+func diffuser(errMap map[coord]float64, d diffusion) quantizerFunction {
 	return func(x int, y int, c color.Color) color.Color {
 		p := coord{x: x, y: y}
 		l := luminence(c) + errMap[p]
@@ -156,6 +148,18 @@ func simpleErrorDiffusion() quantizerFunction {
 	}
 }
 
+func simpleErrorDiffusion() quantizerFunction {
+	errMap := make(map[coord]float64)
+	d := diffusion{
+		divisor: 2.0,
+		matrix: map[coord]float64{
+			{x: 1, y: 0}: 1.0,
+			{x: 0, y: 1}: 1.0,
+		},
+	}
+	return diffuser(errMap, d)
+}
+
 func floydSteinberg() quantizerFunction {
 	errMap := make(map[coord]float64)
 	d := diffusion{
@@ -167,17 +171,7 @@ func floydSteinberg() quantizerFunction {
 			{x: 1, y: 1}:  1.0,
 		},
 	}
-	return func(x int, y int, c color.Color) color.Color {
-		p := coord{x: x, y: y}
-		l := luminence(c) + errMap[p]
-		delete(errMap, p) // don't let the error map grow too big
-		if l > 0.5 {
-			applyError(d, l-1.0, p, errMap)
-			return color.White
-		}
-		applyError(d, l, p, errMap)
-		return color.Black
-	}
+	return diffuser(errMap, d)
 }
 
 func jarvisJudiceNinke() quantizerFunction {
@@ -201,17 +195,7 @@ func jarvisJudiceNinke() quantizerFunction {
 			{x: 2, y: 2}:  1.0,
 		},
 	}
-	return func(x int, y int, c color.Color) color.Color {
-		p := coord{x: x, y: y}
-		l := luminence(c) + errMap[p]
-		delete(errMap, p) // don't let the error map grow too big
-		if l > 0.5 {
-			applyError(d, l-1.0, p, errMap)
-			return color.White
-		}
-		applyError(d, l, p, errMap)
-		return color.Black
-	}
+	return diffuser(errMap, d)
 }
 
 func atkinson() quantizerFunction {
@@ -227,17 +211,7 @@ func atkinson() quantizerFunction {
 			{x: 0, y: 2}:  1.0,
 		},
 	}
-	return func(x int, y int, c color.Color) color.Color {
-		p := coord{x: x, y: y}
-		l := luminence(c) + errMap[p]
-		delete(errMap, p) // don't let the error map grow too big
-		if l > 0.5 {
-			applyError(d, l-1.0, p, errMap)
-			return color.White
-		}
-		applyError(d, l, p, errMap)
-		return color.Black
-	}
+	return diffuser(errMap, d)
 }
 
 // That is, "relative luminance": https://en.wikipedia.org/wiki/Relative_luminance.