package main

import (
    "errors"
    "image"
    "image/jpeg"
    "image/png"
    "mime"
    "net/http"
    "os"
)

func compressImage(imagePath string) error {
    file, err := os.Open(imagePath)
    if err != nil {
        return err
    }
    defer file.Close()

    // 讀取文件的前512個(gè)字節(jié)
    buffer := make([]byte, 512)
    _, err = file.Read(buffer)
    if err != nil {
        return err
    }
    file.Seek(0, 0)

    // 根據(jù)MIME類型檢查
    contentType := http.DetectContentType(buffer)

    var img image.Image
    var format string
    switch contentType {
    case "image/jpeg":
        img, err = jpeg.Decode(file)
        format = "jpeg"
    case "image/png":
        img, err = png.Decode(file)
        format = "png"
    default:
        return nil
    }

    if err != nil {
        return err
    }

    // 關(guān)閉并重新打開文件進(jìn)行壓縮
    file.Close()
    file, err = os.OpenFile(imagePath, os.O_WRONLY|os.O_TRUNC, 0644)
    if err != nil {
        return err
    }
    defer file.Close()

    var opt jpeg.Options
    opt.Quality = 75 // 設(shè)置壓縮質(zhì)量為75

    switch format {
    case "jpeg":
        err = jpeg.Encode(file, img, &opt)
    case "png":
        encoder := png.Encoder{CompressionLevel: png.BestCompression}
        err = encoder.Encode(file, img)
    }

    return err
}

func main() {
    imagePath := "/tmp/1.png"
    err := compressImage(imagePath)
    if err != nil {
        println("Error compressing image:", err.Error())
    } else {
        println("Image compressed successfully")
    }
}