x/image/font: rendering texts in Arabic #27281
Description
What version of Go are you using (go version)?
go version go1.11 darwin/amd64
Does this issue reproduce with the latest release?
Yes
What operating system and processor architecture are you using (go env)?
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/hajimehoshi/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/hajimehoshi/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/hajimehoshi/fonttest/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/b7/w11sqqrx7kx6fqfbn24wdsmh0000gn/T/go-build758210799=/tmp/go-build -gno-record-gcc-switches -fno-common"
What did you do?
I tested to render a text in Arabic language:
package main
import (
"flag"
"image"
"image/color"
"image/draw"
"image/png"
"io/ioutil"
"os"
"strings"
"github.com/golang/freetype/truetype"
"github.com/pkg/browser"
"golang.org/x/image/font"
"golang.org/x/image/math/fixed"
)
const (
// https://www.unicode.org/udhr/
text = "قوقحلاو ةماركلا يف نيواستم ارًارحأ سانلا عيمج دلوي."
)
func run() error {
const (
ox = 16
oy = 16
)
width := 640
height := 16*len(strings.Split(strings.TrimSpace(text), "\n")) + 8
dst := image.NewRGBA(image.Rect(0, 0, width, height))
draw.Draw(dst, dst.Bounds(), image.NewUniform(color.White), image.ZP, draw.Src)
// I tested an arg "/Library/Fonts/Al Nile.ttc" on macOS.
f, err := ioutil.ReadFile(os.Args[1])
if err != nil {
return err
}
tt, err := truetype.Parse(f)
if err != nil {
return err
}
face := truetype.NewFace(tt, &truetype.Options{
Size: 16,
DPI: 72,
Hinting: font.HintingFull,
})
d := font.Drawer{
Dst: dst,
Src: image.NewUniform(color.Black),
Face: face,
Dot: fixed.P(ox, oy),
}
for _, l := range strings.Split(text, "\n") {
d.DrawString(l)
d.Dot.X = fixed.I(ox)
d.Dot.Y += face.Metrics().Height
}
path := "example.png"
fout, err := os.Create(path)
if err != nil {
return err
}
defer fout.Close()
if err := png.Encode(fout, d.Dst); err != nil {
return err
}
if err := browser.OpenFile(path); err != nil {
return err
}
return nil
}
func main() {
flag.Parse()
if err := run(); err != nil {
panic(err)
}
}What did you expect to see?
The text is rendered correctly in an image.
What did you see instead?
The text is rendered wrongly:
I was also wondering how to render texts in complex languages like Thai or Hindi.
