Golang图像处理：学习如何进行图片的拉伸和几何变换

package main

import (
    "image"
    "image/color"
    "image/jpeg"
    "image/png"
    "log"
    "math"
    "os"

    "github.com/gonum/matrix/mat64"
)

// 读取图像文件
func loadImage(filename string) (image.Image, error) {
    file, err := os.Open(filename)
    if err != nil {
        return nil, err
    }
    defer file.Close()
    img, _, err := image.Decode(file)
    return img, err
}

// 保存图像文件
func saveImage(img image.Image, format, filename string) error {
    file, err := os.Create(filename)
    if err != nil {
        return err
    }
    defer file.Close()
    switch format {
    case "jpeg":
        return jpeg.Encode(file, img, &jpeg.Options{Quality: 100})
    case "png":
        return png.Encode(file, img)
    default:
        return nil
    }
}

// 拉伸图像
func stretchImage(img image.Image, width, height int) image.Image {
    newImg := image.NewRGBA(image.Rect(0, 0, width, height))
    for y := 0; y < height; y++ {
        for x := 0; x < width; x++ {
            srcX := int(float64(x) / float64(width) * float64(img.Bounds().Dx()))
            srcY := int(float64(y) / float64(height) * float64(img.Bounds().Dy()))
            newImg.Set(x, y, img.At(srcX, srcY))
        }
    }
    return newImg
}

// 几何变换
func geometricTransformation(img image.Image, theta float64) image.Image {
    width, height := img.Bounds().Dx(), img.Bounds().Dy()
    cosTheta := math.Cos(theta)
    sinTheta := math.Sin(theta)
    M := mat64.NewDense(3, 3, nil)
    M.Set(0, 0, cosTheta)
    M.Set(0, 1, sinTheta)
    M.Set(0, 2, 0)
    M.Set(1, 0, -sinTheta)
    M.Set(1, 1, cosTheta)
    M.Set(1, 2, 0)
    M.Set(2, 0, 0)
    M.Set(2, 1, 0)
    M.Set(2, 2, 1)
    newImg := image.NewRGBA(image.Rect(0, 0, width, height))
    for y := 0; y < height; y++ {
        for x := 0; x < width; x++ {
            v := mat64.NewVector(3, []float64{float64(x), float64(y), 1})
            res := mat64.NewVector(3, nil)
            res.MulVec(M, v)
            srcX := int(res.At(0, 0) / res.At(2, 0))
            srcY := int(res.At(1, 0) / res.At(2, 0))
            if srcX >= 0 && srcX < width && srcY >= 0 && srcY < height {
                newImg.Set(x, y, img.At(srcX, srcY))
            } else {
                newImg.Set(x, y, color.White)
            }
        }
    }
    return newImg
}

func main() {
    // 读取图像
    img, err := loadImage("input.jpg")
    if err != nil {
        log.Fatal(err)
    }

    // 拉伸图像
    stretchedImg := stretchImage(img, 500, 500)
    err = saveImage(stretchedImg, "jpeg", "stretched.jpg")
    if err != nil {
        log.Fatal(err)
    }

    // 几何变换
    geometricImg := geometricTransformation(img, 0.5)
    err = saveImage(geometricImg, "jpeg", "geometric.jpg")
    if err != nil {
        log.Fatal(err)
    }
}