From 1588b49f0d3d121334470c0a7ed56fb39ebd966a Mon Sep 17 00:00:00 2001
From: Drahoslav <drahoslav@yo2.cz>
Date: Wed, 10 Jan 2018 20:21:07 +0100
Subject: [PATCH] Optimize svg output sligtly

---
 draw2dsvg/converters.go | 77 +++++++++++++++++++++++++++++++++--------
 draw2dsvg/gc.go         |  2 +-
 2 files changed, 63 insertions(+), 16 deletions(-)

diff --git a/draw2dsvg/converters.go b/draw2dsvg/converters.go
index 70c6ace..2b6d462 100644
--- a/draw2dsvg/converters.go
+++ b/draw2dsvg/converters.go
@@ -12,6 +12,7 @@ import (
 	"image/color"
 	"image/png"
 	"math"
+	"strconv"
 	"strings"
 )
 
@@ -19,19 +20,19 @@ func toSvgRGBA(c color.Color) string {
 	r, g, b, a := c.RGBA()
 	r, g, b, a = r>>8, g>>8, b>>8, a>>8
 	if a == 255 {
-		return fmt.Sprintf("#%02X%02X%02X", r, g, b)
+		return optiSprintf("#%02X%02X%02X", r, g, b)
 	}
-	return fmt.Sprintf("rgba(%v,%v,%v,%.3f)", r, g, b, float64(a)/255)
+	return optiSprintf("rgba(%v,%v,%v,%f)", r, g, b, float64(a)/255)
 }
 
 func toSvgLength(l float64) string {
-	return fmt.Sprintf("%.4f", l)
+	return optiSprintf("%f", l)
 }
 
 func toSvgArray(nums []float64) string {
 	arr := make([]string, len(nums))
 	for i, num := range nums {
-		arr[i] = fmt.Sprintf("%.4f", num)
+		arr[i] = optiSprintf("%f", num)
 	}
 	return strings.Join(arr, ",")
 }
@@ -49,16 +50,16 @@ func toSvgPathDesc(p *draw2d.Path) string {
 	for i, cmp := range p.Components {
 		switch cmp {
 		case draw2d.MoveToCmp:
-			parts[i] = fmt.Sprintf("M %.4f,%.4f", ps[0], ps[1])
+			parts[i] = optiSprintf("M %f,%f", ps[0], ps[1])
 			ps = ps[2:]
 		case draw2d.LineToCmp:
-			parts[i] = fmt.Sprintf("L %.4f,%.4f", ps[0], ps[1])
+			parts[i] = optiSprintf("L %f,%f", ps[0], ps[1])
 			ps = ps[2:]
 		case draw2d.QuadCurveToCmp:
-			parts[i] = fmt.Sprintf("Q %.4f,%.4f %.4f,%.4f", ps[0], ps[1], ps[2], ps[3])
+			parts[i] = optiSprintf("Q %f,%f %f,%f", ps[0], ps[1], ps[2], ps[3])
 			ps = ps[4:]
 		case draw2d.CubicCurveToCmp:
-			parts[i] = fmt.Sprintf("C %.4f,%.4f %.4f,%.4f %.4f,%.4f", ps[0], ps[1], ps[2], ps[3], ps[4], ps[5])
+			parts[i] = optiSprintf("C %f,%f %f,%f %f,%f", ps[0], ps[1], ps[2], ps[3], ps[4], ps[5])
 			ps = ps[6:]
 		case draw2d.ArcToCmp:
 			cx, cy := ps[0], ps[1] // center
@@ -83,15 +84,15 @@ func toSvgPathDesc(p *draw2d.Path) string {
 			// dirty hack to ensure whole arc is drawn
 			// if start point equals end point
 			if sweep == 1 {
-				x += 0.001 * sinfi
-				y += 0.001 * -cosfi
+				x += 0.0001 * sinfi
+				y += 0.0001 * -cosfi
 			} else {
-				x += 0.001 * sinfi
-				y += 0.001 * cosfi
+				x += 0.0001 * sinfi
+				y += 0.0001 * cosfi
 			}
 
 			// rx ry x-axis-rotation large-arc-flag sweep-flag x y
-			parts[i] = fmt.Sprintf("A %.4f %.4f %v %v %v %.4f %.4f",
+			parts[i] = optiSprintf("A %f %f %v %v %v %F %F",
 				rx, ry, 0, large, sweep, x, y,
 			)
 			ps = ps[6:]
@@ -108,9 +109,9 @@ func toSvgTransform(mat draw2d.Matrix) string {
 	}
 	if mat.IsTranslation() {
 		x, y := mat.GetTranslation()
-		return fmt.Sprintf("translate(%f,%f)", x, y)
+		return optiSprintf("translate(%f,%f)", x, y)
 	}
-	return fmt.Sprintf("matrix(%f,%f,%f,%f,%f,%f)",
+	return optiSprintf("matrix(%f,%f,%f,%f,%f,%f)",
 		mat[0], mat[1], mat[2], mat[3], mat[4], mat[5],
 	)
 }
@@ -122,3 +123,49 @@ func imageToSvgHref(image image.Image) string {
 	out += base64.RawStdEncoding.EncodeToString(pngBuf.Bytes())
 	return out
 }
+
+// Do the same thing as fmt.Sprintf
+// except it uses the optimal precition for floats: (0-3) for f and (0-6) for F
+// eg.:
+// optiSprintf("%f", 3.0)               => fmt.Sprintf("%.0f", 3.0)
+// optiSprintf("%f", 3.33)              => fmt.Sprintf("%.2f", 3.33)
+// optiSprintf("%f", 3.3001)            => fmt.Sprintf("%.1f", 3.3001)
+// optiSprintf("%f", 3.333333333333333) => fmt.Sprintf("%.3f", 3.333333333333333)
+// optiSprintf("%F", 3.333333333333333) => fmt.Sprintf("%.6f", 3.333333333333333)
+func optiSprintf(format string, a ...interface{}) string {
+	chunks := strings.Split(format, "%")
+	newChunks := make([]string, len(chunks))
+	for i, chunk := range chunks {
+		if i != 0 {
+			verb := chunk[0]
+			if verb == 'f' || verb == 'F' {
+				num := a[i-1].(float64)
+				p := strconv.Itoa(getPrec(num, verb == 'F'))
+				chunk = strings.Replace(chunk, string(verb), "."+p+"f", 1)
+			}
+		}
+		newChunks[i] = chunk
+	}
+	format = strings.Join(newChunks, "%")
+	return fmt.Sprintf(format, a...)
+}
+
+func getPrec(num float64, better bool) int {
+	max := 3
+	eps := 0.0005
+	if better {
+		max = 6
+		eps = 0.0000005
+	}
+	prec := 0
+	for math.Mod(num, 1) > eps {
+		num *= 10
+		eps *= 10
+		prec++
+	}
+
+	if max < prec {
+		return max
+	}
+	return prec
+}
diff --git a/draw2dsvg/gc.go b/draw2dsvg/gc.go
index 50cc7bf..2af5ad7 100644
--- a/draw2dsvg/gc.go
+++ b/draw2dsvg/gc.go
@@ -369,7 +369,7 @@ func (gc *GraphicContext) DrawImage(image image.Image) {
 ///////////////////////////////////////
 // TODO implement following methods (or remove if not neccesary)
 
-// GetFontName gets the current FontData as a string
+// GetFontName gets the current FontData with fontSize as a string
 func (gc *GraphicContext) GetFontName() string {
 	fontData := gc.Current.FontData
 	return fmt.Sprintf("%s:%d:%d:%d", fontData.Name, fontData.Family, fontData.Style, gc.Current.FontSize)