How to use Golang to draw straight lines and curves on pictures

package main

import (
    "image"
    "image/color"
    "image/draw"
    "image/jpeg"
    "os"
)

func main() {
    // 打开图片文件
    file, err := os.Open("input.jpg")
    if err != nil {
        panic(err)
    }
    defer file.Close()

    // 解码图片
    img, err := jpeg.Decode(file)
    if err != nil {
        panic(err)
    }

    // 创建一个可绘制区域
    bounds := img.Bounds()
    drawImg := image.NewRGBA(bounds)

    // 复制图片内容到绘制区域
    draw.Draw(drawImg, bounds, img, bounds.Min, draw.Src)

    // 绘制直线
    lineColor := color.RGBA{255, 0, 0, 255} // 红色直线
    start := image.Point{100, 100}         // 起点坐标
    end := image.Point{300, 300}           // 终点坐标
    drawLine(drawImg, start, end, lineColor)

    // 保存绘制后的图片
    outFile, err := os.Create("output.jpg")
    if err != nil {
        panic(err)
    }
    defer outFile.Close()

    jpeg.Encode(outFile, drawImg, &jpeg.Options{Quality: 100})
}

// 绘制直线
func drawLine(img draw.Image, start, end image.Point, c color.Color) {
    dx := abs(end.X - start.X)
    dy := abs(end.Y - start.Y)
    sx := 0
    if start.X < end.X {
        sx = 1
    } else {
        sx = -1
    }
    sy := 0
    if start.Y < end.Y {
        sy = 1
    } else {
        sy = -1
    }
    err := dx - dy

    for {
        img.Set(start.X, start.Y, c)
        if start.X == end.X && start.Y == end.Y {
            break
        }
        e2 := 2 * err
        if e2 > -dy {
            err -= dy
            start.X += sx
        }
        if e2 < dx {
            err += dx
            start.Y += sy
        }
    }
}

// 计算绝对值
func abs(x int) int {
    if x < 0 {
        return -x
    }
    return x
}

package main

import (
    "image"
    "image/color"
    "image/draw"
    "image/jpeg"
    "math"
    "os"
)

func main() {
    // 打开图片文件
    file, err := os.Open("input.jpg")
    if err != nil {
        panic(err)
    }
    defer file.Close()

    // 解码图片
    img, err := jpeg.Decode(file)
    if err != nil {
        panic(err)
    }

    // 创建一个可绘制区域
    bounds := img.Bounds()
    drawImg := image.NewRGBA(bounds)

    // 复制图片内容到绘制区域
    draw.Draw(drawImg, bounds, img, bounds.Min, draw.Src)

    // 绘制贝塞尔曲线
    curveColor := color.RGBA{0, 255, 0, 255} // 绿色曲线
    controlPoints := []image.Point{
        {100, 100}, // 控制点1
        {200, 300}, // 控制点2
        {300, 100}, // 控制点3
    }
    drawCurve(drawImg, controlPoints, curveColor)

    // 保存绘制后的图片
    outFile, err := os.Create("output.jpg")
    if err != nil {
        panic(err)
    }
    defer outFile.Close()

    jpeg.Encode(outFile, drawImg, &jpeg.Options{Quality: 100})
}

// 绘制贝塞尔曲线
func drawCurve(img draw.Image, controlPoints []image.Point, c color.Color) {
    step := 0.01 // 步长
    stepNum := int(1 / step) + 1

    for t := 0; t <= stepNum; t++ {
        tf := float64(t) * step
        x, y := calculateBezier(controlPoints, tf)

        if x >= 0 && y >= 0 && x < img.Bounds().Dx() && y < img.Bounds().Dy() {
            img.Set(x, y, c)
        }
    }
}

// 计算贝塞尔曲线上的点
func calculateBezier(controlPoints []image.Point, t float64) (x, y int) {
    n := len(controlPoints) - 1
    x = 0
    y = 0

    for i := 0; i <= n; i++ {
        coeff := binomialCoefficient(n, i) * math.Pow(1-t, float64(n-i)) * math.Pow(t, float64(i))
        x += int(float64(controlPoints[i].X) * coeff)
        y += int(float64(controlPoints[i].Y) * coeff)
    }

    return x, y
}

// 计算二项式系数
func binomialCoefficient(n, k int) int {
    return factorial(n) / (factorial(k) * factorial(n-k))
}

// 计算阶乘
func factorial(n int) int {
    result := 1
    for i := 1; i <= n; i++ {
        result *= i
    }
    return result
}