注意：如水印文字是中文，需要中文字体
字体下载链接：https://fonts.google.com

package imgUtilsimport ("golang.org/x/image/font""golang.org/x/image/math/fixed""math""image""image/color""image/draw""io/ioutil""github.com/golang/freetype/truetype""github.com/disintegration/imaging"
)/**添加文本水印到图片img：图片数据watermarkText：水印内容fontPath：字体路径angle：旋转角度*/
func AddWatermark(img image.Image, watermarkText string, fontPath string, angle float64) (image.Image, error) {// 加载字体fontBytes, err := ioutil.ReadFile(fontPath)if err != nil {return nil, err}f, err := truetype.Parse(fontBytes)if err != nil {return nil, err}// 创建面部字体face := truetype.NewFace(f, &truetype.Options{Size:    24,DPI:     72,Hinting: font.HintingNone,})// 计算文本大小（调整密度）txtSize := int(math.Ceil(45.0 * 90.0 / 96.0))// 创建水印图像bounds := img.Bounds()wm := image.NewRGBA(bounds)draw.Draw(wm, bounds, img, bounds.Min, draw.Src)// 设置字体颜色col := color.RGBA{R: 0, G: 0, B: 0, A: 20}// 循环绘制水印for y := txtSize; y < bounds.Dy(); y += txtSize * 4 {for x := txtSize; x < bounds.Dx(); x += txtSize * 4 {// 创建临时图像temp := image.NewRGBA(image.Rect(0, 0, txtSize*4, txtSize*4))d := &font.Drawer{Dst:  temp,Src:  image.NewUniform(col),Face: face,Dot:  fixed.P(0, txtSize),}d.DrawString(watermarkText)// 旋转临时图像rotated := imaging.Rotate(temp, angle, color.NRGBA{0, 0, 0, 0})// 绘制旋转后的图像到原始图像draw.Draw(wm, image.Rect(x, y, x+rotated.Bounds().Dx(), y+rotated.Bounds().Dy()), rotated, image.Point{}, draw.Over)}}return wm, nil
}