Golang 圖片上繪制文字

本文轉載自查看原文 2016-03-10 08:35 5565 Go語言/ 驗證碼

之前介紹過使用 FreeType-go 來繪制字（http://www.cnblogs.com/ghj1976/p/3445568.html），現在相關的包被做了整合，主要是整合到了 github.com/golang/freetype 和 golang.org/x/image/font 這里了，所以就有了這篇博客。

例子代碼在： https://github.com/golang/freetype/blob/master/example/freetype/main.go

package main

import (
    "bufio"
    "flag"
    "fmt"
    "image"
    "image/color"
    "image/draw"
    "image/png"
    "io/ioutil"
    "log"
    "os"

    "github.com/golang/freetype"
    "golang.org/x/image/font"
)

var (
    dpi      = flag.Float64("dpi", 72, "screen resolution in Dots Per Inch")
    fontfile = flag.String("fontfile", "../../testdata/luxisr.ttf", "filename of the ttf font")
    hinting = flag.String("hinting", "none", "none | full")
    size     = flag.Float64("size", 12, "font size in points")
    spacing = flag.Float64("spacing", 1.5, "line spacing (e.g. 2 means double spaced)")
    wonb     = flag.Bool("whiteonblack", false, "white text on a black background")
)

var text = []string{
    "’Twas brillig, and the slithy toves",
    "測試中文字 ……&^_^",
    "Did gyre and gimble in the wabe;",
    "All mimsy were the borogoves,",
    "And the mome raths outgrabe.",
    "",
    "“Beware the Jabberwock, my son!",
    "The jaws that bite, the claws that catch!",
    "Beware the Jubjub bird, and shun",
    "The frumious Bandersnatch!”",
    "",
    "He took his vorpal sword in hand:",
    "Long time the manxome foe he sought—",
    "So rested he by the Tumtum tree,",
    "And stood awhile in thought.",
    "",
    "And as in uffish thought he stood,",
    "The Jabberwock, with eyes of flame,",
    "Came whiffling through the tulgey wood,",
    "And burbled as it came!",
    "",
    "One, two! One, two! and through and through",
    "The vorpal blade went snicker-snack!",
    "He left it dead, and with its head",
    "He went galumphing back.",
    "",
    "“And hast thou slain the Jabberwock?",
    "Come to my arms, my beamish boy!",
    "O frabjous day! Callooh! Callay!”",
    "He chortled in his joy.",
    "",
    "’Twas brillig, and the slithy toves",
    "Did gyre and gimble in the wabe;",
    "All mimsy were the borogoves,",
    "And the mome raths outgrabe.",
}

func main() {
    flag.Parse()

    // Read the font data.
    fontBytes, err := ioutil.ReadFile(*fontfile)
    if err != nil {
        log.Println(err)
        return
    }
    f, err := freetype.ParseFont(fontBytes)
    if err != nil {
        log.Println(err)
        return
    }

    // Initialize the context.
    fg, bg := image.Black, image.White
    ruler := color.RGBA{0xdd, 0xdd, 0xdd, 0xff}
    if *wonb {
        fg, bg = image.White, image.Black
        ruler = color.RGBA{0x22, 0x22, 0x22, 0xff}
    }
    rgba := image.NewRGBA(image.Rect(0, 0, 640, 480))
    draw.Draw(rgba, rgba.Bounds(), bg, image.ZP, draw.Src)
    c := freetype.NewContext()
    c.SetDPI(*dpi)
    c.SetFont(f)
    c.SetFontSize(*size)
    c.SetClip(rgba.Bounds())
    c.SetDst(rgba)
    c.SetSrc(fg)
    switch *hinting {
    default:
        c.SetHinting(font.HintingNone)
    case "full":
        c.SetHinting(font.HintingFull)
    }

    // Draw the guidelines.
    for i := 0; i < 200; i++ {
        rgba.Set(10, 10+i, ruler)
        rgba.Set(10+i, 10, ruler)
    }

    // Draw the text.
    pt := freetype.Pt(10, 10+int(c.PointToFixed(*size)>>6))
    for _, s := range text {
        _, err = c.DrawString(s, pt)
        if err != nil {
            log.Println(err)
            return
        }
        pt.Y += c.PointToFixed(*size * *spacing)
    }

    // Save that RGBA image to disk.
    outFile, err := os.Create("out.png")
    if err != nil {
        log.Println(err)
        os.Exit(1)
    }
    defer outFile.Close()
    b := bufio.NewWriter(outFile)
    err = png.Encode(b, rgba)
    if err != nil {
        log.Println(err)
        os.Exit(1)
    }
    err = b.Flush()
    if err != nil {
        log.Println(err)
        os.Exit(1)
    }
    fmt.Println("Wrote out.png OK.")
}