Image/gif Package usage in Golang

This is a creation in Article, where the information may have evolved or changed.

GIF package enables decoding and encoding of GIF images

Func Decode (R io. Reader) (image. Image, error)//decode reads a GIF image from R, and then returns the image. The image is the first embedded diagram.

Func decodeconfig (R io. Reader) (image. Config, error)//decodeconfig does not need to decode the entire image to return the global color model and the size of the GIF image.

Type Config struct {    ColorModel    color. Model    Width, Height int}

Config returns the image's color model and size

Func Encode (w io. Writer, M image. Image, O *options) error//To write picture m in GIF mode W

The type Options struct {//numcolors is the maximum color used in a picture, and its range is 1-256numcolors int//Quantizer is often used to generate palettes through numcolors, palette. Plan9 is used to replace nil Quantizerquantizer draw. quantizer//Drawer i is used to convert the source picture into the desired palette, draw. Floydsteinberg is used instead of an empty drawer.drawer draw. Drawer}

Func encodeall (w io. Writer, g *gif) error//The picture is written in W according to the number of cycles and delays specified between frames and frames

Type GIF struct {    Image     []*image. paletted//Continuous picture    delay     []int             //continuous delay time, each frame unit is 1% seconds, the value in Delay indicates the time interval of its two images dynamic display    Loopcount int               / /cycle times, if 0 is always cycled. }

Func decodeall (R io. Reader) (*gif, error)//decodeall reads a GIF picture from R and returns the frame and time information for the order

A simple example of how to make a GIF image with a GIF package, draw two vertical intersecting dynamic plots (if you want to get a complex GIF image, you can set more complex drawing lines and color patterns to get complex graphics):

Package Mainimport ("FMT" "Image" "Image/color" "Image/color/palette" "Image/gif" "Net/http" "OS") Func Main () {http. Handlefunc ("/display", display) Err: = http. Listenandserve (": 9100", nil) if err! = Nil {fmt. PRINTLN (ERR)}}func display (W http. Responsewriter, Q *http. Request) {f1, err: = OS. Create ("Test.gif") if err! = Nil {fmt. PRINTLN (Err)}defer F1. Close () P1: = image. newpaletted (image. Rect (0, 0, palette),. PLAN9) for x: = 0; x < 100; X + + {for y: = 0; y < y++ {P1. Set (x, y, color. Rgba{uint8 (x), Uint8 (y), 255, 255})}}p2: = image. newpaletted (image. Rect (0, 0, Palette, a),. PLAN9) for x: = 0; x < 100; X + + {for y: = 0; y < y++ {P2. Set (x, a, color. Rgba{uint8 (x * x% 255), uint8 (y * y% 255), 0, 255})}}g1: = &gif. Gif{image:     []*image. PALETTED{P1, P2},delay:     []int{30, 30},loopcount:0,}gif. Encodeall (W, G1)  //browser displays GIF. Encodeall (F1, G1)//save to file}

Animated GIF images are as follows:

Of course, you can also use the existing image to generate GIF, the code is as follows:

Package Mainimport ("FMT" "Image" "Image/color/palette" "Image/draw" "Image/gif" "Image/jpeg" "Image/png" "Net/http" "Os ") func Main () {http. Handlefunc ("/display", display) Err: = http. Listenandserve (": 9100", nil) if err! = Nil {fmt. PRINTLN (ERR)}}func display (W http. Responsewriter, Q *http. Request) {f, err: = OS. Open ("Test.jpeg") if err! = Nil {fmt. PRINTLN (Err)}defer f.close () g, err: = JPEG. Decode (f) if err! = Nil {fmt. PRINTLN (Err)}f2, err: = OS. Open ("123.png") if err! = Nil {fmt. PRINTLN (Err)}defer f.close () g2, err: = png. Decode (F2) if err! = Nil {fmt. PRINTLN (Err)}f1, err: = OS. Create ("Test.gif") if err! = Nil {fmt. PRINTLN (Err)}defer F1. Close () P1: = image. newpaletted (image. Rect (0, 0, $, palette). PLAN9) draw. Draw (P1, p1. Bounds (), G, image. ZP, Draw. SRC)//Add picture P2: = image. newpaletted (image. Rect (0, 0, $, palette). PLAN9) draw. Draw (P2, p2. Bounds (), G2, image. ZP, Draw. SRC)//Add picture g1: = &gif. Gif{image: []*image. PALETTED{P1, P2},delay: []int{30, 30},loopcount:0,}gif. Encodeall (W, G1) GIF.encodeall (F1, G1)} 

The resulting GIF picture is as follows: