Go语言学习之image、image/color、image/png、image/jpeg包(the way to go)

生命不止，继续 go go go !!!

golang同样为我们提供了很多关于图片处理的标准库，这里与大家一起学习分享。

image package

作用：
Package image implements a basic 2-D image library.
image包实现了一个基本的2D图像库.

方法：
func NewNRGBA

func NewNRGBA(r Rectangle) *NRGBA

NewNRGBA returns a new NRGBA image with the given bounds.

什么是NRGBA？
NRGBA is an in-memory image whose At method returns color.NRGBA values.

type NRGBA struct {        Pix []uint8        Stride int        Rect Rectangle}

func (*NRGBA) Set

func (p *NRGBA) Set(x, y int, c color.Color)

设定指定位置的color，image/color稍后会介绍。

func Rect

func Rect(x0, y0, x1, y1 int) Rectangle

Rect is shorthand for Rectangle{Pt(x0, y0), Pt(x1, y1)}.

image/color package

作用：
Package color implements a basic color library.

func (NRGBA) RGBA

func (c NRGBA) RGBA() (r, g, b, a uint32)

func DecodeConfig

func DecodeConfig(r io.Reader) (Config, string, error)

DecodeConfig decodes the color model and dimensions of an image that has been encoded in a registered format.
更通俗说就是获得image的信息。

image/png package

作用：
Package png implements a PNG image decoder and encoder。

func (*Encoder) Encode

func (enc *Encoder) Encode(w io.Writer, m image.Image) error

编码png文件。

image/jpeg package

作用：
Package jpeg implements a JPEG image decoder and encoder.

func Encode

func Encode(w io.Writer, m image.Image, o *Options) error

编码JPG文件。

应用

生成图片

package mainimport "image"import "image/color"import "image/png"import "os"func main() {    // Create an 100 x 50 image    img := image.NewRGBA(image.Rect(0, 0, 100, 50))    // Draw a red dot at (2, 3)    img.Set(2, 3, color.RGBA{255, 0, 0, 255})    // Save to out.png    f, _ := os.OpenFile("out.png", os.O_WRONLY|os.O_CREATE, 0600)    defer f.Close()    png.Encode(f, img)}

运行结果，就是生成了一张png文件。

生成复杂色彩的图片

package mainimport (    "fmt"    "image"    "image/color"    "image/png"    "math"    "os")type Circle struct {    X, Y, R float64}func (c *Circle) Brightness(x, y float64) uint8 {    var dx, dy float64 = c.X - x, c.Y - y    d := math.Sqrt(dx*dx+dy*dy) / c.R    if d > 1 {        return 0    } else {        return 255    }}func main() {    var w, h int = 280, 240    var hw, hh float64 = float64(w / 2), float64(h / 2)    r := 40.0    θ := 2 * math.Pi / 3    cr := &Circle{hw - r*math.Sin(0), hh - r*math.Cos(0), 60}    cg := &Circle{hw - r*math.Sin(θ), hh - r*math.Cos(θ), 60}    cb := &Circle{hw - r*math.Sin(-θ), hh - r*math.Cos(-θ), 60}    m := image.NewRGBA(image.Rect(0, 0, w, h))    for x := 0; x < w; x++ {        for y := 0; y < h; y++ {            c := color.RGBA{                cr.Brightness(float64(x), float64(y)),                cg.Brightness(float64(x), float64(y)),                cb.Brightness(float64(x), float64(y)),                255,            }            m.Set(x, y, c)        }    }    f, err := os.OpenFile("rgb.png", os.O_WRONLY|os.O_CREATE, 0600)    if err != nil {        fmt.Println(err)        return    }    defer f.Close()    png.Encode(f, m)}

运行结果：

获取一张图片的尺寸

package mainimport (    "fmt"    "image"    _ "image/jpeg"    _ "image/png"    "os")func main() {    width, height := getImageDimension("rgb.png")    fmt.Println("Width:", width, "Height:", height)}func getImageDimension(imagePath string) (int, int) {    file, err := os.Open(imagePath)    defer file.Close()    if err != nil {        fmt.Fprintf(os.Stderr, "%v\n", err)    }    image, _, err := image.DecodeConfig(file)    if err != nil {        fmt.Fprintf(os.Stderr, "%s: %v\n", imagePath, err)    }    return image.Width, image.Height}

生成缩略图
借助github开源项目：
https://github.com/disintegration/imaging
文档地址：
http://godoc.org/github.com/disintegration/imaging