Golang : Print UTF-8 fonts on image example


12103 views 16th November 2016


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://www.socketloop.com/tutorials/golang-how-to-print-rune-unicode-utf-8-and-non-ascii-cjk-chinese-japanese-korean-characters

https://github.com/golang/freetype/blob/master/example/freetype/main.go

https://godoc.org/github.com/golang/freetype

  See also : Golang : Put UTF8 text on OpenCV video capture image frame





By Adam Ng

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