用golang给图片加水印

前言

大前天上班的时候，坐在旁边的同事需要一批有水印的图片来测试模型。然后我就主动站出来……

他问我怎么加，我说用golang可以。可为啥我不用更容易实现的Python呢……可能是为了装逼。

代码

WaterMark.go | Gist

package mainimport ( "bytes" "fmt" "strings" "io/ioutil" "os" "path" "math" "math/rand" "time" "image" "image/color" "image/draw" "image/jpeg" "image/png" "github.com/gonum/plot/vg" "github.com/gonum/plot/vg/vgimg")func init() { rand.Seed(time.Now().UnixNano())}// WaterMark for adding a watermark on the imagefunc WaterMark(img image.Image, markText string) (image.Image, error) { // image's length to canvas's length bounds := img.Bounds() w := vg.Length(bounds.Max.X) * vg.Inch / vgimg.DefaultDPI h := vg.Length(bounds.Max.Y) * vg.Inch / vgimg.DefaultDPI diagonal := vg.Length(math.Sqrt(float64(w*w + h*h))) // create a canvas, which width and height are diagonal c := vgimg.New(diagonal, diagonal) // draw image on the center of canvas rect := vg.Rectangle{} rect.Min.X = diagonal/2 - w/2 rect.Min.Y = diagonal/2 - h/2 rect.Max.X = diagonal/2 + w/2 rect.Max.Y = diagonal/2 + h/2 c.DrawImage(rect, img) // make a fontStyle, which width is vg.Inch * 0.7 fontStyle, _ := vg.MakeFont("Courier", vg.Inch*0.7) // repeat the markText markTextWidth := fontStyle.Width(markText) unitText := markText for markTextWidth <= diagonal { markText += " " + unitText markTextWidth = fontStyle.Width(markText) } // set the color of markText c.SetColor(color.RGBA{0, 0, 0, 122}) // set a random angle between 0 and π/2 θ := math.Pi * rand.Float64() / 2 c.Rotate(θ) // set the lineHeight and add the markText lineHeight := fontStyle.Extents().Height * 1 for offset := -2 * diagonal; offset < 2*diagonal; offset += lineHeight { c.FillString(fontStyle, vg.Point{X: 0, Y: offset}, markText) } // canvas writeto jpeg // canvas.img is private // so use a buffer to transfer jc := vgimg.PngCanvas{Canvas: c} buff := new(bytes.Buffer) jc.WriteTo(buff) img, _, err := image.Decode(buff) if err != nil { return nil, err } // get the center point of the image ctp := int(diagonal * vgimg.DefaultDPI / vg.Inch / 2) // cutout the marked image size := bounds.Size() bounds = image.Rect(ctp-size.X/2, ctp-size.Y/2, ctp+size.X/2, ctp+size.Y/2) rv := image.NewRGBA(bounds) draw.Draw(rv, bounds, img, bounds.Min, draw.Src) return rv, nil}// MarkingPicture for marking picture with textfunc MarkingPicture(filepath, text string) (image.Image, error) { f, err := os.Open(filepath) if err != nil { return nil, err } defer f.Close() img, _, err := image.Decode(f) if err != nil { return nil, err } img, err = WaterMark(img, text) if err != nil { return nil, err } return img, nil}func writeTo(img image.Image, ext string) (rv *bytes.Buffer, err error) { ext = strings.ToLower(ext) rv = new(bytes.Buffer) switch ext { case ".jpg", ".jpeg": err = jpeg.Encode(rv, img, &jpeg.Options{Quality: 100}) case ".png": err = png.Encode(rv, img) } return rv, err}func main() { if len(os.Args) < 3 { panic(fmt.Errorf("Please using like this:$ %s [file or directory] [text]", os.Args[0])) } target := os.Args[1] text := os.Args[2] if stat, err := os.Stat(target); err == nil && stat.IsDir() { files, _ := ioutil.ReadDir(target) for _, fn := range files { img, err := MarkingPicture(path.Join(target, fn.Name()), text) if err != nil { continue } ext := path.Ext(fn.Name()) base := strings.Split(fn.Name(), ".")[0] + "_marked" f, err := os.Create(base + ext) if err != nil { panic(err) } buff, err := writeTo(img, ext) if err != nil { panic(err) } if _, err = buff.WriteTo(f); err != nil { panic(err) } } } else { img, err := MarkingPicture(target, text) if err != nil { panic(err) } ext := path.Ext(target) base := strings.Split(path.Base(target), ".")[0] + "_marked" f, err := os.Create(base + ext) if err != nil { panic(err) } buff, err := writeTo(img, ext) if err != nil { panic(err) } if _, err = buff.WriteTo(f); err != nil { panic(err) } }} 图片效果