golang：图片的切割与缩小

Bertha 。 2023-03-13 05:26 4阅读 0赞

package main
    
    import (
    	"errors"
    	"fmt"
    	"golang.org/x/image/bmp"
    	"image"
    	"image/gif"
    	"image/jpeg"
    	"image/png"
    	"io"
    	"log"
    	"os"
    	"strings"
    
    	"github.com/nfnt/resize"
    )
    
    func main() {
        
    	src := "png.png"
    	dst := strings.Replace(src, ".", "_aa.", 1)
    	fmt.Println("src=", src, " dst=", dst)
    	fIn, _ := os.Open(src)
    	defer fIn.Close()
    
    	fOut, _ := os.Create(dst)
    	defer fOut.Close()
    
    	err := Clip(fIn, fOut, 0,0, 0, 0, 150, 150, 100)
    	 if err != nil {
        
    	 	panic(err)
    	 }
    /*	w, h, err := Scale(fIn, fOut, 150, 150, 100)
    	if err != nil {
    		panic(err)
    	}
    	fmt.Println(w, h)*/
    }
    
    
    //补上缺失的代码
    //* Clip 图片裁剪
    //* 入参:图片输入、输出、缩略图宽、缩略图高、Rectangle{Pt(x0, y0), Pt(x1, y1)}，精度
    //* 规则:如果精度为0则精度保持不变
    //*
    //* 返回:error
    // */
    func Clip(in io.Reader, out io.Writer, wi, hi, x0, y0, x1, y1, quality int) (err error) {
        
    	err = errors.New("unknow error")
    	defer func() {
        
    		if r := recover(); r != nil {
        
    			log.Println(r)
    		}
    	}()
    	var origin image.Image
    	var fm string
    	origin, fm, err = image.Decode(in)
    	if err != nil {
        
    		log.Println(err)
    		return err
    	}
    
    	if wi == 0 || hi == 0 {
        
    		wi = origin.Bounds().Max.X
    		hi = origin.Bounds().Max.Y
    	}
    	var canvas image.Image
    	if wi != origin.Bounds().Max.X {
        
    		//先缩略
    		canvas = resize.Thumbnail(uint(wi), uint(hi), origin, resize.Lanczos3)
    	} else {
        
    		canvas = origin
    	}
    
    
    	switch fm {
        
    	case "jpeg":
    		img := canvas.(*image.YCbCr)
    		subImg := img.SubImage(image.Rect(x0, y0, x1, y1)).(*image.YCbCr)
    		return jpeg.Encode(out, subImg, &jpeg.Options{
        quality})
    	case "png":
    		switch canvas.(type) {
        
    		case *image.NRGBA:
    			img := canvas.(*image.NRGBA)
    			subImg := img.SubImage(image.Rect(x0, y0, x1, y1)).(*image.NRGBA)
    			return png.Encode(out, subImg)
    		case *image.RGBA:
    			img := canvas.(*image.RGBA)
    			subImg := img.SubImage(image.Rect(x0, y0, x1, y1)).(*image.RGBA)
    			return png.Encode(out, subImg)
    		}
    	case "gif":
    		img := canvas.(*image.Paletted)
    		subImg := img.SubImage(image.Rect(x0, y0, x1, y1)).(*image.Paletted)
    		return gif.Encode(out, subImg, &gif.Options{
        })
    	case "bmp":
    		img := canvas.(*image.RGBA)
    		subImg := img.SubImage(image.Rect(x0, y0, x1, y1)).(*image.RGBA)
    		return bmp.Encode(out, subImg)
    	default:
    		return errors.New("ERROR FORMAT")
    	}
    	return nil
    }
    
    /*
    * Scale 缩略图生成
    * 入参:图片输入、输出，缩略图宽、高，精度
    * 规则: 如果width 或 hight其中有一个为0，则大小不变 如果精度为0则精度保持不变
    * 返回:缩略图真实宽、高、error
     */
    func Scale(in io.Reader, out io.Writer, width, height, quality int) (int, int, error) {
        
    	defer func() {
        
    		if r := recover(); r != nil {
        
    			log.Println(r)
    		}
    	}()
    	var (
    		w, h int
    	)
    	origin, fm, err := image.Decode(in)
    	if err != nil {
        
    		log.Println(err)
    		return 0, 0, err
    	}
    	if width == 0 || height == 0 {
        
    		width = origin.Bounds().Max.X
    		height = origin.Bounds().Max.Y
    	}
    	if quality == 0 {
        
    		quality = 100
    	}
    	canvas := resize.Thumbnail(uint(width), uint(height), origin, resize.Lanczos3)
    
    	//return jpeg.Encode(out, canvas, &jpeg.Options{quality})
    	w = canvas.Bounds().Dx()
    	h = canvas.Bounds().Dy()
    	switch fm {
        
    	case "jpeg":
    		return w, h, jpeg.Encode(out, canvas, &jpeg.Options{
        quality})
    	case "png":
    		return w, h, png.Encode(out, canvas)
    	case "gif":
    		return w, h, gif.Encode(out, canvas, &gif.Options{
        })
    	//case "bmp":  //被我注释掉的是x/image/bmp
    	//	return w, h, bmp.Encode(out, canvas)
    	default:
    		return w, h, errors.New("ERROR FORMAT")
    	}
    	return w, h, nil
    }