Code zum Bild-Golang

go get golang.org/x/tools/cmd/godoc

godoc -html package > package.html

package main

import (
    "bufio"
    "fmt"
    "image"
    "image/draw"
    "image/png"
    "os"
    "strings"

    "golang.org/x/net/html"
)

func main() {
    htmlFile, err := os.Open("package.html")
    if err != nil {
        fmt.Println(err)
        return
    }
    defer htmlFile.Close()

    doc, err := html.Parse(htmlFile)
    if err != nil {
        fmt.Println(err)
        return
    }

    imgFile, err := os.Create("package.png")
    if err != nil {
        fmt.Println(err)
        return
    }
    defer imgFile.Close()

    // 初始化画布
    bounds := image.Rect(0, 0, 800, 600)
    rgba := image.NewRGBA(bounds)
    draw.Draw(rgba, bounds, image.White, image.Point{}, draw.Src)

    // 渲染HTML
    renderHTML(rgba, doc)

    // 保存为PNG图片
    png.Encode(imgFile, rgba)
}

func renderHTML(rgba *image.RGBA, n *html.Node) {
    if n.Type == html.ElementNode {
        switch n.Data {
        case "html":
            renderHTML(rgba, n.FirstChild)
        case "body":
            renderHTML(rgba, n.FirstChild)
        case "pre":
            renderCodeBlock(rgba, n.FirstChild.Data, n.Attr)
        }
    }

    if n.NextSibling != nil {
        renderHTML(rgba, n.NextSibling)
    }
}

func renderCodeBlock(rgba *image.RGBA, code string, attrs []html.Attribute) {
    // 解析HTML属性
    style := ""
    for _, attr := range attrs {
        if attr.Key == "style" {
            style = attr.Val
        }
    }

    // 绘制文本
    x := 10
    y := 20
    scanner := bufio.NewScanner(strings.NewReader(code))
    scanner.Split(bufio.ScanLines)
    for scanner.Scan() {
        drawText(rgba, scanner.Text(), x, y, style)
        y += 16
    }
}

func drawText(rgba *image.RGBA, text string, x, y int, style string) {
    // 绘制文本
    font := loadFont(style)
    drawer := &fontDrawer{
        dst:  rgba,
        src:  image.NewUniform(color.Black),
        face: truetype.NewFace(font, &truetype.Options{Size: 16}),
    }
    drawer.DrawString(text, fixed.Point26_6{X: fixed.Int26_6(x * 64), Y: fixed.Int26_6(y * 64)}, &drawerOptions{})
}

type fontDrawer struct {
    dst  draw.Image
    src  image.Image
    face font.Face
}

type drawerOptions struct{}

func (d *fontDrawer) ColorModel() color.Model {
    return color.AlphaModel
}

func (d *fontDrawer) Bounds() image.Rectangle {
    return d.dst.Bounds()
}

func (d *fontDrawer) Draw(dst draw.Image, r image.Rectangle, src image.Image, sp image.Point) {
    // 绘制文本
    dr, mask, _, _ := d.face.GlyphBounds('.')
    for _, c := range "x" + text {
        glyphIndex := d.face.Index(c)
        glyphAdvance, _, _, _ := d.face.GlyphAdvance(glyphIndex, draw.Src)
        glyphBounds, _, _, glyphBaseline := d.face.GlyphBounds(glyphIndex)
        if c != 'x' {
            draw.DrawMask(d.dst, image.Rectangle{
                Min: image.Point{
                    X: (r.Min.X / 64) + ((glyphBounds.Min.X + glyphBaseline.X) / 64),
                    Y: (r.Min.Y / 64) - ((glyphBounds.Max.Y + glyphBaseline.Y) / 64),
                },
                Max: image.Point{
                    X: (r.Min.X / 64) + ((glyphBounds.Max.X + glyphBaseline.X) / 64),
                    Y: (r.Min.Y / 64) - ((glyphBounds.Min.Y + glyphBaseline.Y) / 64),
                },
            }, d.src, image.Point{}, &fontMask{mask, fixed.P(glyphBounds.Min.X+glyphBaseline.X, glyphBounds.Min.Y+glyphBaseline.Y)}, draw.Over)
        }
        r.Min.X += int(glyphAdvance >> 6)
        if r.Min.X >= r.Max.X {
            break
        }
    }
}

func (d *fontDrawer) DrawString(s string, p fixed.Point26_6, _ *drawerOptions) {
    d.Draw(d.dst, d.dst.Bounds(), d.src, image.Point{
        X: int(p.X >> 6),
        Y: int(p.Y >> 6),
    })
}

type fontMask struct {
    mask image.Image
    fp   fixed.Point
}

func (m *fontMask) ColorModel() color.Model {
    return color.AlphaModel
}

func (m *fontMask) Bounds() image.Rectangle {
    return m.mask.Bounds().Add(image.Point{X: m.fp.X.Round(), Y: m.fp.Y.Round()})
}

func (m *fontMask) At(x, y int) color.Color {
    ax := (x - m.fp.X.Round())
    ay := (y - m.fp.Y.Round())
    if ax < 0 || ay < 0 || ax >= m.mask.Bounds().Dx() || ay >= m.mask.Bounds().Dy() {
        return color.Alpha{}
    }
    return color.Alpha{A: m.mask.(*image.Alpha).AlphaAt(ax, ay).A}
}

func loadFont(style string) *truetype.Font {
    // 加载字体
    // TODO: 解析font-family和font-size属性
    fontBytes, err := ioutil.ReadFile("DejaVuSansMono.ttf")
    if err != nil {
        panic(err)
    }
    font, err := truetype.Parse(fontBytes)
    if err != nil {
        panic(err)
    }
    return font
}