前言

sdl2 提供了快速旋转和翻转的功能, 这一节我们就来看看如何使用

代码

代码这边我把 texture 结构体单独拎出来放到一个文件里, 代码量多了之后就要注意工程管理了

package main

import (
    "github.com/veandco/go-sdl2/img"
    "github.com/veandco/go-sdl2/sdl"
)

type Texture struct {
    t *sdl.Texture
    W int32
    H int32
}

func (this *Texture) LoadFromFile(path string) bool {
    img, err := img.Load(path)
    if err != nil {
        panic(err)
    }
    this.t, err = Grender.CreateTextureFromSurface(img)
    if err != nil {
        panic(err)
    }
    this.W = img.W
    this.H = img.H
    img.Free()

    return true
}

func (this *Texture) Render(src, dst *sdl.Rect, angle float64, center *sdl.Point, flip sdl.RendererFlip) {
    Grender.CopyEx(this.t, src, dst, angle, center, flip)
}

func (this *Texture) setColor(r, g, b uint8) {
    this.t.SetColorMod(r, g, b)
}

func (this *Texture) SetAlpha(a uint8) {
    this.t.SetAlphaMod(a)
}

func (this *Texture) SetBlendMode(blend sdl.BlendMode) {
    this.t.SetBlendMode(blend)
}

func (this *Texture) Free() {
    this.t.Destroy()
}

func (this *Texture) GetW() int32 {
    return this.W
}

func (this *Texture) GetH() int32 {
    return this.H
}

1. 注意这里有一个新的函数 CopyEx, 它比 Copy 函数多了几个参数, 就是用来控制图片旋转角度这些的

package main

import (
    "github.com/veandco/go-sdl2/sdl"
)

const (
    W = 670
    H = 520
)

var (
    Gwindow *sdl.Window
    Grender *sdl.Renderer
    texture *Texture
)

func init() {
    sdl.Init(sdl.INIT_EVERYTHING)
    Gwindow, err := sdl.CreateWindow("test", sdl.WINDOWPOS_UNDEFINED, sdl.WINDOWPOS_UNDEFINED, W, H, sdl.WINDOW_SHOWN)
    if err != nil {
        panic(err)
    }
    Grender, err = sdl.CreateRenderer(Gwindow, -1, sdl.RENDERER_ACCELERATED)
    if err != nil {
        panic(err)
    }
    texture = &Texture{}
    texture.LoadFromFile("../asserts/image/arrow.png")
}

func main() {
    flipType := sdl.FLIP_NONE
    degree := float64(0)
    running := true
    for running {
        for event := sdl.PollEvent(); event != nil; event = sdl.PollEvent() {
            switch t := event.(type) {
            case *sdl.QuitEvent:
                println("Quit")
                running = false
                break
            case *sdl.KeyboardEvent:
                if t.State == sdl.PRESSED {
                    switch t.Keysym.Sym {
                    case sdl.K_a:
                        degree -= 60
                    case sdl.K_d:
                        degree += 60
                    case sdl.K_q:
                        flipType = sdl.FLIP_HORIZONTAL
                    case sdl.K_w:
                        flipType = sdl.FLIP_NONE
                    case sdl.K_e:
                        flipType = sdl.FLIP_VERTICAL
                    }
                }
            }
        }
        Grender.SetDrawColor(128, 128, 128, 255)
        Grender.Clear()
        dst := &sdl.Rect{(W - texture.GetW()) / 2, (H - texture.GetH()) / 2, 100, 100}
        texture.Render(nil, dst, degree, nil, flipType)

        Grender.Present()
        sdl.Delay(16)
    }
    free()
}

func free() {
    texture.Free()
    Grender.Destroy()
    Gwindow.Destroy()
    sdl.Quit()
}

1. 这段代码的功能就是根据用户输入的不同按键, 将图片旋转不同的角度
2. 主循环中读取按键输入, 根据不同的按键设置 degree 角度, flipType 翻转类型
3. 最后调用 Render 进行渲染

源码 https://gitee.com/fcsvr/tank.git