Go语言图片解码与内存管理：解决循环处理大量文件时的内存溢出问题

package main

import (
    "flag"
    "image/png"
    "io/ioutil"
    "log"
    "os"
    "path"
    "runtime" // 引入 runtime 包
)

// greyLevel 函数用于计算图片中灰色像素的百分比
func greyLevel(fname string) (float64, string) {
    f, err := os.Open(fname)
    if err != nil {
        return -1.0, "can't open file"
    }
    defer f.Close()

    // 使用 png.Decode 解码图片
    i, err := png.Decode(f)
    if err != nil {
        return -1.0, "unable to decode"
    }

    bounds := i.Bounds()

    var lo uint32 = 122 // 低灰色RGB值
    var hi uint32 = 134 // 高灰色RGB值
    var gpix float64    // 灰色像素计数
    var opix float64    // 其他像素计数
    var tpix float64    // 总像素计数

    for x := bounds.Min.X; x < bounds.Max.X; x++ {
        for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
            r, g, b, _ := i.At(x, y).RGBA()
            // 将16位颜色值转换为8位进行比较
            r8, g8, b8 := r>>8, g>>8, b>>8 
            if (r8 > lo && r8 < hi) &&
                (g8 > lo && g8 < hi) &&
                (b8 > lo && b8 < hi) {
                gpix++
            } else {
                opix++
            }
            tpix++
        }
    }
    return (gpix / tpix) * 100, ""
}

func main() {
    srcDir := flag.String("s", "", "Directory containing image files.")
    threshold := flag.Float64("t", 65.0, "Threshold (in percent) of grey pixels.")
    flag.Parse()

    dirlist, direrr := ioutil.ReadDir(*srcDir)
    if direrr != nil {
        log.Fatalf("Error reading %s: %s\n", *srcDir, direrr)
    }

    for f := range dirlist {
        src := path.Join(*srcDir, dirlist[f].Name())

        level, msg := greyLevel(src)

        if msg != "" {
            log.Printf("error processing %s: %s\n", src, msg)
            continue
        }

        if level >= *threshold {
            log.Printf("%s is grey (%2.2f%%)\n", src, level)
        } else {
            log.Printf("%s is not grey (%2.2f%%)\n", src, level)
        }

        // 在每次处理完图片后显式调用垃圾回收
        runtime.GC() 
    }
}

func main() {
    // ... (省略部分代码) ...

    for f := range dirlist {
        src := path.Join(*srcDir, dirlist[f].Name())

        level, msg := greyLevel(src)

        if msg != "" {
            log.Printf("error processing %s: %s\n", src, msg)
            continue
        }

        if level >= *threshold {
            log.Printf("%s is grey (%2.2f%%)\n", src, level)
        } else {
            log.Printf("%s is not grey (%2.2f%%)\n", src, level)
        }

        // 显式调用垃圾回收
        runtime.GC() 
    }
}