Golang : Print UTF-8 fonts on image example
Problem:
You need to write UTF-8 characters such as Icelandic,Chinese, Japanese, Korean, Russian or symbols like © Ø ® ß ◊ ¥ Ô º ™ € ¢ ∞ § Ω on an image with Go. For cases such as using it as a label on a button. How to do that?
Solution:
Use the wqy-zenhei.ttf
font and github.com/golang/freetype
to draw the UTF-8 characters on the image.
Download the font from http://www.slackware.com/~alien/slackbuilds/wqy-zenhei-font-ttf/build/wqy-zenhei-0.4.23-1.tar.gz and extract the wqy-zenhei.ttf
to the same folder as this program.
Run the code example that follows and view the output utf8text.png
file with an image viewer.
Here you go!
package main
import (
"bufio"
"fmt"
"image"
"image/color"
"image/draw"
"image/png"
"io/ioutil"
"os"
"github.com/golang/freetype"
"github.com/golang/freetype/truetype"
)
var (
backgroundWidth = 650
backgroundHeight = 150
utf8FontFile = "wqy-zenhei.ttf"
utf8FontSize = float64(15.0)
spacing = float64(1.5)
dpi = float64(72)
ctx = new(freetype.Context)
utf8Font = new(truetype.Font)
red = color.RGBA{255, 0, 0, 255}
blue = color.RGBA{0, 0, 255, 255}
white = color.RGBA{255, 255, 255, 255}
black = color.RGBA{0, 0, 0, 255}
background *image.RGBA
// more color at https://github.com/golang/image/blob/master/colornames/table.go
)
func main() {
// download font from http://www.slackware.com/~alien/slackbuilds/wqy-zenhei-font-ttf/build/wqy-zenhei-0.4.23-1.tar.gz
// extract wqy-zenhei.ttf to the same folder as this program
// Read the font data - for this example, we load the Chinese fontfile wqy-zenhei.ttf,
// but it will display any utf8 fonts such as Russian, Japanese, Korean, etc as well.
// some utf8 fonts cannot be displayed. You need to use your own language .ttf file
fontBytes, err := ioutil.ReadFile(utf8FontFile)
if err != nil {
fmt.Println(err)
return
}
utf8Font, err = freetype.ParseFont(fontBytes)
if err != nil {
fmt.Println(err)
return
}
fontForeGroundColor, fontBackGroundColor := image.NewUniform(black), image.NewUniform(white)
background = image.NewRGBA(image.Rect(0, 0, backgroundWidth, backgroundHeight))
draw.Draw(background, background.Bounds(), fontBackGroundColor, image.ZP, draw.Src)
ctx = freetype.NewContext()
ctx.SetDPI(dpi) //screen resolution in Dots Per Inch
ctx.SetFont(utf8Font)
ctx.SetFontSize(utf8FontSize) //font size in points
ctx.SetClip(background.Bounds())
ctx.SetDst(background)
ctx.SetSrc(fontForeGroundColor)
var UTF8text = []string{
`English - Hello, Chinese - 你好, Russian - Здравствуйте, Korean - 여보세요, Greek - Χαίρετε`,
`Tajik - Салом, Japanese - こんにちは, Icelandic - Halló, Belarusian - добры дзень`,
`symbols - © Ø ® ß ◊ ¥ Ô º ™ € ¢ ∞ § Ω`,
}
// Draw the text to the background
pt := freetype.Pt(10, 10+int(ctx.PointToFixed(utf8FontSize)>>6))
// not all utf8 fonts are supported by wqy-zenhei.ttf
// use your own language true type font file if your language cannot be printed
for _, str := range UTF8text {
_, err := ctx.DrawString(str, pt)
if err != nil {
fmt.Println(err)
return
}
pt.Y += ctx.PointToFixed(utf8FontSize * spacing)
}
// Save
outFile, err := os.Create("utf8text.png")
if err != nil {
fmt.Println(err)
os.Exit(-1)
}
defer outFile.Close()
buff := bufio.NewWriter(outFile)
err = png.Encode(buff, background)
if err != nil {
fmt.Println(err)
os.Exit(-1)
}
// flush everything out to file
err = buff.Flush()
if err != nil {
fmt.Println(err)
os.Exit(-1)
}
fmt.Println("Save to utf8text.png")
}
NOTES:
Check out https://github.com/pbnjay/pixfont as well.
Not all languages fonts are available. See the readme section extracted from wqy-zenhei's README on language coverage.
III. Language Coverage
The following table is based on the locale data provided by fontconfig
(generated by langcover.pl from Dejavu Project
http://dejavu.sourceforge.net/wiki/index.php/Font_utilities).
ZenHei
aa Afar 100% (62/62)
ab Abkhazia 75% (68/90)
af Afrikaans 100% (69/69)
am Amharic (0/264)
ar Arabic (0/125)
as (0/89)
ast Asturian 100% (72/72)
ava Avaric 100% (67/67)
ay Aymara 100% (60/60)
az Azerbaijani 85% (127/148)
az-ir Azerbaijani in Iran (0/130)
ba Bashkir 78% (64/82)
bam Bambara 90% (54/60)
be Byelorussian 100% (68/68)
bg Bulgarian 100% (60/60)
bh Bihari (Devanagari script) (0/68)
bho Bhojpuri (Devanagari script) (0/68)
bi Bislama 100% (58/58)
bin Edo or Bini 92% (72/78)
bn Bengali (0/89)
bo Tibetan (0/95)
br Breton 100% (64/64)
bs Bosnian 85% (53/62)
bua Buriat (Buryat) 94% (66/70)
ca Catalan 100% (74/74)
ce Chechen 100% (67/67)
ch Chamorro 100% (58/58)
chm Mari (Lower Cheremis / Upper Cheremis) 86% (66/76)
chr Cherokee (0/85)
co Corsican 100% (85/85)
cs Czech 80% (66/82)
cu Old Church Slavonic 71% (74/103)
cv Chuvash 89% (66/74)
cy Welsh 87% (68/78)
da Danish 100% (70/70)
de German 100% (60/60)
dz Dzongkha (0/95)
el Greek 100% (70/70)
en English 100% (73/73)
eo Esperanto 81% (52/64)
es Spanish 100% (67/67)
et Estonian 93% (60/64)
eu Basque 100% (56/56)
fa Persian (0/129)
fi Finnish 93% (59/63)
fj Fijian 100% (52/52)
fo Faroese 100% (68/68)
fr French 100% (85/85)
ful Fulah (Fula) 87% (54/62)
fur Friulian 100% (66/66)
fy Frisian 100% (75/75)
ga Irish 77% (62/80)
gd Scots Gaelic 100% (70/70)
gez Ethiopic (Geez) (0/218)
gl Galician 100% (66/66)
gn Guarani 94% (66/70)
gu Gujarati (0/78)
gv Manx Gaelic 100% (54/54)
ha Hausa 86% (52/60)
haw Hawaiian 92% (58/63)
he Hebrew (0/27)
hi Hindi (Devanagari script) (0/68)
ho Hiri Motu 100% (52/52)
hr Croatian 85% (53/62)
hu Hungarian 94% (66/70)
hy Armenian (0/77)
ia Interlingua 100% (52/52)
ibo Igbo 89% (52/58)
id Indonesian 100% (54/54)
ie Interlingue 100% (52/52)
ik Inupiaq (Inupiak, Eskimo) 100% (68/68)
io Ido 100% (52/52)
is Icelandic 100% (70/70)
it Italian 100% (73/73)
iu Inuktitut (0/161)
ja Japanese 100% (6538/6538)
ka Georgian (0/33)
kaa Kara-Kalpak (Karakalpak) 84% (66/78)
ki Kikuyu 92% (52/56)
kk Kazakh 84% (65/77)
kl Greenlandic 95% (77/81)
km Khmer (0/70)
kn Kannada (0/80)
ko Korean 100% (2443/2443)
kok Kokani (Devanagari script) (0/68)
ks Kashmiri (Devanagari script) (0/68)
ku Kurdish 90% (58/64)
ku-ir Kurdish in Iran (0/32)
kv Komi (Komi-Permyak/Komi-Siryan) 97% (68/70)
kw Cornish 89% (57/64)
ky Kirgiz 94% (66/70)
la Latin 83% (57/68)
lb Luxembourgish (Letzeburgesch) 100% (75/75)
lez Lezghian (Lezgian) 100% (67/67)
ln Lingala 90% (73/81)
lo Lao (0/65)
lt Lithuanian 75% (53/70)
lv Latvian 73% (57/78)
mg Malagasy 100% (56/56)
mh Marshallese 88% (55/62)
mi Maori 89% (57/64)
mk Macedonian 90% (38/42)
ml Malayalam (0/78)
mn Mongolian (0/130)
mo Moldavian 95% (122/128)
mr Marathi (Devanagari script) (0/68)
mt Maltese 91% (66/72)
my Burmese (Myanmar) (0/48)
nb Norwegian Bokmal 100% (70/70)
nds Low Saxon 100% (59/59)
ne Nepali (Devanagari script) (0/68)
nl Dutch 100% (83/83)
nn Norwegian Nynorsk 100% (76/76)
no Norwegian (Bokmal) 100% (70/70)
ny Chichewa 100% (54/54)
oc Occitan 100% (70/70)
om Oromo or Galla 100% (52/52)
or Oriya (0/79)
os Ossetic 100% (66/66)
pa Punjabi (Gurumukhi script) (0/63)
pl Polish 81% (57/70)
ps-af Pashto in Afghanistan (0/49)
ps-pk Pashto in Pakistan (0/49)
pt Portuguese 100% (83/83)
rm Rhaeto-Romance (Romansch) 100% (66/66)
ro Romanian 90% (56/62)
ru Russian 100% (66/66)
sa Sanskrit (Devanagari script) (0/68)
sah Yakut 86% (66/76)
sco Scots 92% (52/56)
se North Sami 89% (59/66)
sel Selkup (Ostyak-Samoyed) 100% (66/66)
sh Serbo-Croatian 100% (76/76)
si Sinhala (Sinhalese) (0/77)
sk Slovak 80% (69/86)
sl Slovenian 85% (53/62)
sm Samoan 100% (53/53)
sma South Sami 100% (60/60)
smj Lule Sami 100% (60/60)
smn Inari Sami 89% (61/68)
sms Skolt Sami 78% (63/80)
so Somali 100% (52/52)
sq Albanian 100% (56/56)
sr Serbian 100% (76/76)
sv Swedish 100% (68/68)
sw Swahili 100% (52/52)
syr Syriac (0/45)
ta Tamil (0/48)
te Telugu (0/80)
tg Tajik 84% (66/78)
th Thai (0/87)
ti-er Eritrean Tigrinya (0/256)
ti-et Ethiopian Tigrinya (0/282)
tig Tigre (0/221)
tk Turkmen 89% (66/74)
tl Tagalog (0/19)
tn Tswana 100% (56/56)
to Tonga 100% (53/53)
tr Turkish 92% (65/70)
ts Tsonga 100% (52/52)
tt Tatar 86% (66/76)
tw Twi 79% (58/73)
tyv Tuvinian 94% (66/70)
ug Uighur (0/125)
uk Ukrainian 97% (70/72)
ur Urdu (0/145)
uz Uzbek 88% (60/68)
ven Venda 83% (52/62)
vi Vietnamese 43% (85/194)
vo Volapuk 100% (54/54)
vot Votic 93% (58/62)
wa Walloon 100% (70/70)
wen Sorbian languages (lower and upper) 76% (58/76)
wo Wolof 100% (66/66)
xh Xhosa 100% (52/52)
yap Yapese 100% (58/58)
yi Yiddish (0/27)
yo Yoruba 77% (92/119)
zh-936 GBK Chinese national standard 100% (21921/21920)
zh-cn Chinese (simplified) 100% (6765/6765)
zh-hk Chinese Hong Kong Supplementary Character Set 100% (2213/2213)
zh-mo Chinese in Macau 100% (2213/2213)
zh-sg Chinese in Singapore 100% (6765/6765)
zh-tw Chinese (traditional) 100% (13063/13063)
zu Zulu 100% (52/52)
Happy coding!
References:
https://github.com/golang/freetype/blob/master/example/freetype/main.go
See also : Golang : Put UTF8 text on OpenCV video capture image frame
By Adam Ng
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