图片缩放

import (
    "fmt"
    "github.com/nfnt/resize"
    "image"
    _ "image/gif"
    _ "image/jpeg"
    "image/png"
    "math"
    "os"
)



const DEFAULT_MAX_WIDTH float64 = 320
const DEFAULT_MAX_HEIGHT float64 = 240

// 计算图片缩放后的尺寸
func calculateRatioFit(srcWidth, srcHeight int) (int, int) {
    ratio := math.Min(DEFAULT_MAX_WIDTH/float64(srcWidth), DEFAULT_MAX_HEIGHT/float64(srcHeight))
    return int(math.Ceil(float64(srcWidth) * ratio)), int(math.Ceil(float64(srcHeight) * ratio))
}

// 生成缩略图
func makeThumbnail(imagePath, savePath string) (string, error) {

    file, _ := os.Open(imagePath)
    defer file.Close()

    img, _, err := image.Decode(file)
    if err != nil {
        return "",err
    }

    b := img.Bounds()
    width := b.Max.X
    height := b.Max.Y

    w, h := calculateRatioFit(width, height)

    fmt.Println("width = ", width, " height = ", height)
    fmt.Println("w = ", w, " h = ", h)

    // 调用resize库进行图片缩放
    m := resize.Resize(uint(w), uint(h), img, resize.Lanczos3)

    // 需要保存的文件
    imgfile, _ := os.Create(savePath)
    defer imgfile.Close()

    // 以PNG格式保存文件
    err = png.Encode(imgfile, m)
    if err != nil {
        return "",err
    }

    return "",nil
}

图片转码

import (
    "encoding/base64"
    "fmt"
    "image"
    "os"
    _ "image/gif"
    _ "image/jpeg"
    _ "image/png"
    "image/png"
)

func main() {   
    file, err := os.Open("image/19155559_E3nk.jpg")
    defer file.Close()
    img, _, _ := image.Decode(file)
    // 以PNG格式保存文件
    imgfile, _ := os.Create("image/19155559_E3nk.png")
    defer imgfile.Close()
    err = png.Encode(imgfile, img)
    fmt.Println("err = ", err)
}