fixed PNG font rendering for high DPI

drawing/draw.go

@@ -19,11 +19,15 @@ package drawing
 
 import (
 	"fmt"
+	"log"
 	"sort"
 	"strings"
 	"unicode"
 
+	"github.com/golang/freetype/truetype"
 	"github.com/joiningdata/lollipops/data"
+	"golang.org/x/image/font"
+	"golang.org/x/image/math/fixed"
 )
 
 type diagram struct {
@@ -192,10 +196,10 @@ func (s *Settings) prepare(changelist []string, g *data.GraphicResponse) *diagra
 		label := ""
 
 		if swidth > 10 && s.DomainLabelStyle != "off" {
-			if len(r.Metadata.Description) > 1 && float64(MeasureFont(r.Metadata.Description, 12)) < (swidth-s.TextPadding) {
+			if len(r.Metadata.Description) > 1 && float64(s.MeasureFont(r.Metadata.Description, 12)) < (swidth-s.TextPadding) {
 				// we can fit the full description! nice!
 				label = r.Metadata.Description
-			} else if float64(MeasureFont(r.Text, 12)) < (swidth - s.TextPadding) {
+			} else if float64(s.MeasureFont(r.Text, 12)) < (swidth - s.TextPadding) {
 				label = r.Text
 			} else if s.DomainLabelStyle == "truncate" {
 				didOutput := false
@@ -216,7 +220,7 @@ func (s *Settings) prepare(changelist []string, g *data.GraphicResponse) *diagra
 						if i == 0 {
 							pre = ""
 						}
-						if float64(MeasureFont(pre+parts[i]+post, 12)) < (swidth - s.TextPadding) {
+						if float64(s.MeasureFont(pre+parts[i]+post, 12)) < (swidth - s.TextPadding) {
 							label = pre + parts[i] + post
 							didOutput = true
 							break
@@ -229,7 +233,7 @@ func (s *Settings) prepare(changelist []string, g *data.GraphicResponse) *diagra
 					sub := r.Text
 					for mx := len(r.Text) - 2; mx > 0; mx-- {
 						sub = strings.TrimFunc(r.Text[:mx], unicode.IsPunct) + ".."
-						if float64(MeasureFont(sub, 12)) < (swidth - s.TextPadding) {
+						if float64(s.MeasureFont(sub, 12)) < (swidth - s.TextPadding) {
 							break
 						}
 					}
@@ -246,7 +250,22 @@ func (s *Settings) prepare(changelist []string, g *data.GraphicResponse) *diagra
 	}
 
 	if s.legendInfo != nil {
-		s.GraphicHeight += float64(1+len(s.legendInfo)) * 14.0
+
+		fface := truetype.NewFace(theFont, &truetype.Options{
+			Size:    float64(12.0),
+			DPI:     float64(DefaultSettings.dpi),
+			Hinting: font.HintingFull,
+		})
+		// get font height in px
+		bounds, _, ok := fface.GlyphBounds('M')
+		if !ok {
+			log.Fatalf("unable to determine font bounds!")
+		}
+		// add 2px line spacing
+		fontH := bounds.Max.Sub(bounds.Min).Y + fixed.I(2)
+		s.GraphicHeight += float64(2 * fontH.Ceil())
+
+		s.GraphicHeight += float64(len(s.legendInfo)*fontH.Ceil()) * 1.2
 		for key, color := range s.legendInfo {
 			if rename, found := data.MotifNames[key]; found {
 				delete(s.legendInfo, key)

drawing/fonts.go

@@ -74,12 +74,12 @@ func LoadFont(name, path string) error {
 // MeasureFont returns the pixel width of the string s at font size sz.
 // It tries to use system Arial font if possible, but falls back to a
 // conservative ballpark estimate otherwise.
-func MeasureFont(s string, sz int) int {
+func (x *Settings) MeasureFont(s string, sz int) int {
 	// use actual TTF font metrics if available
 	if theFont != nil {
 		myFace := truetype.NewFace(theFont, &truetype.Options{
 			Size: float64(sz),
-			DPI:  float64(DefaultSettings.dpi),
+			DPI:  float64(x.dpi),
 		})
 		d := &font.Drawer{Face: myFace}
 		w := d.MeasureString(s)

drawing/png.go

@@ -214,21 +214,22 @@ func (s *diagram) png(w io.Writer) {
 			}
 			blackFontDrawer.DrawString(spos)
 		}
-		startY += s.AxisHeight
+		startY += s.AxisHeight + float64(fontH.Ceil())
 	}
 
+	legBoxSize := float64(fontH.Ceil())
 	for key, colorstring := range s.legendInfo {
-		startY += 14.0
+		startY += legBoxSize * 1.2
 		// 15% darker than backbone (i.e. disordered color)
 		clr := color.RGBA{0x9E, 0xA0, 0x9A, 0xFF}
 		if key != data.MotifNames["disorder"] {
 			clr = colorFromHex(BlendColorStrings(colorstring, "#FFFFFF"))
 		}
-		drawRectWHShadow(img, 4, startY, 12, 12, clr, 2*s.dpi/72.0)
+		drawRectWHShadow(img, legBoxSize, startY, legBoxSize, legBoxSize, clr, 2*s.dpi/72.0)
 
 		blackFontDrawer.Dot = fixed.Point26_6{
-			X: fixed.I(20),
-			Y: fixed.I(int(startY + 12)), // 12=font height-baseline
+			X: fixed.I(int(legBoxSize)) + fixed.I(int(legBoxSize*1.4)),
+			Y: fixed.I(int(startY + legBoxSize)),
 		}
 		blackFontDrawer.DrawString(key)
 	}

drawing/utils.go

@@ -88,7 +88,7 @@ func (s *Settings) AutoWidth(g *data.GraphicResponse) float64 {
 		send, _ := r.End.Float64()
 
 		aaPart := (send - sstart) / aaLen
-		minTextWidth := float64(MeasureFont(r.Text, 12)) + (s.TextPadding * 2) + 1
+		minTextWidth := float64(s.MeasureFont(r.Text, 12)) + (s.TextPadding * 2) + 1
 
 		ww := minTextWidth / aaPart
 		if ww > w {