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jeffer0323
139 Stars 37 Forks MIT License 14 Commits 4 Opened issues

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We-Canvas

1.We-Canvas之WaveImage

实现细节：

1.js:

``` drawImage:function(data){
var that = this
var p10= data[0][0];   /* 三阶贝塞尔曲线起点坐标值*/
var p11= data[0][1];   /* 三阶贝塞尔曲线第一个控制点坐标值*/
var p12= data[0][2];   /* 三阶贝塞尔曲线第二个控制点坐标值*/
var p13= data[0][3];   /* 三阶贝塞尔曲线终点坐标值*/

var p20= data[1][0];
var p21= data[1][1];
var p22= data[1][2];
var p23= data[1][3];

var p30= data[2][0];
var p31= data[2][1];
var p32= data[2][2];
var p33= data[2][3];

var t = factor.t;

/*计算多项式系数 （下同）*/
var cx1 = 3*(p11.x-p10.x);
var bx1 = 3*(p12.x-p11.x)-cx1;
var ax1 = p13.x-p10.x-cx1-bx1;

var cy1 = 3*(p11.y-p10.y);
var by1 = 3*(p12.y-p11.y)-cy1;
var ay1 = p13.y-p10.y-cy1-by1;

var xt1 = ax1*(t*t*t)+bx1*(t*t)+cx1*t+p10.x;
var yt1 = ay1*(t*t*t)+by1*(t*t)+cy1*t+p10.y;

var cx2 = 3*(p21.x-p20.x);
var bx2 = 3*(p22.x-p21.x)-cx2;
var ax2 = p23.x-p20.x-cx2-bx2;

var cy2 = 3*(p21.y-p20.y);
var by2 = 3*(p22.y-p21.y)-cy2;
var ay2 = p23.y-p20.y-cy2-by2;

var xt2 = ax2*(t*t*t)+bx2*(t*t)+cx2*t+p20.x;
var yt2 = ay2*(t*t*t)+by2*(t*t)+cy2*t+p20.y;

var cx3 = 3*(p31.x-p30.x);
var bx3 = 3*(p32.x-p31.x)-cx3;
var ax3 = p33.x-p30.x-cx3-bx3;

var cy3 = 3*(p31.y-p30.y);
var by3 = 3*(p32.y-p31.y)-cy3;
var ay3 = p33.y-p30.y-cy3-by3;

/*计算xt yt的值 */
var xt3 = ax3*(t*t*t)+bx3*(t*t)+cx3*t+p30.x;
var yt3 = ay3*(t*t*t)+by3*(t*t)+cy3*t+p30.y;
factor.t +=factor.speed;
ctx.drawImage("../../images/heart1.png",xt1,yt1,30,30);
ctx.drawImage("../../images/heart2.png",xt2,yt2,30,30);
ctx.drawImage("../../images/heart3.png",xt3,yt3,30,30);
ctx.draw();
if(factor.t>1){
factor.t=0;
cancelAnimationFrame(timer);
that.startTimer();
}else{
timer =requestAnimationFrame(function(){
that.drawImage([[{x:30,y:400},{x:70,y:300},{x:-50,y:150},{x:30,y:0}],[{x:30,y:400},{x:30,y:300},{x:80,y:150},{x:30,y:0}],[{x:30,y:400},{x:0,y:90},{x:80,y:100},{x:30,y:0}]])
})
}}
```

2.原理：

a.通过绘制三条不同的三阶贝塞尔曲线，选取三张图片让其沿着各自的贝塞尔曲线运动，运动轨迹如下图：

b.计算三阶贝塞尔曲线x(t),y(t)的数学表达式。

```cx = 3 * ( x1 - x0 )
bx = 3 * ( x2 - x1 ) - cx
ax = x3 - x0 - cx - bx
cy = 3 * ( y1 - y0 )
by = 3 * ( y2 - y1 ) - cy
ay = y3 - y0 - cy - by

x(t) = ax * t ^ 3 + bx * t ^ 2 + cx * t + x0
y(t) = ay * t ^ 3 + by * t ^ 2 + cy * t + y0```

2.We-Canvas之Particle

实现原理：

"reserve Boolean 非必填。本次绘制是否接着上一次绘制，即reserve参数为false，则在本次调用drawCanvas绘制之前native层应先清空画布再继续绘制；若reserver参数为true，则保留当前画布上的内容，本次调用drawCanvas绘制的内容覆盖在上面，默认 false"

3.We-Canvas之FlappyBird

实现细节：

JS逻辑:

主要包括 小鸟下降逻辑、随机空隙管道逻辑、 单机屏幕事件、碰撞事件、计数逻辑

```birdDown:function(){
ctx.clearRect(0, 0, res.windowWidth, res.windowHeight)
bird.y += bird.factor
ctx.drawImage(birds[Math.floor(Math.random()*2)], bird.x, bird.y, bird.px, bird.px)
ctx.draw()

timer1 = requestAnimationFrame(this.birdDown)
if( bird.y>res.windowHeight){
cancelAnimationFrame(timer1)

}
```

```  pipe:function(){
pipe.x-=pipe.factor
bird.y += bird.factor
if(pipe.x <-pipe.width){
pipe.x = res.windowWidth
gapHeightY = Math.floor(Math.random()*(res.windowHeight-200))+20
}
ctx.drawImage('../../images/flappybird/pipe_down.png', pipe.x, 0, pipe.width, gapHeightY)
ctx.drawImage('../../images/flappybird/pipe_up.png', pipe.x, gapHeightY+gapHeight, pipe.width,          res.windowHeight-gapHeightY-gapHeight)

}
```

```    bird.y -= bird.factor2
//  只需改变bird的y坐标值即可

```

```// 这里加了一个插值数10，目的是为了更贴近碰撞
crash:function(){
bird.cX = bird.x+bird.px-10
bird.cY = bird.y
pipe.cX = pipe.x
pipe.cY = gapHeightY
if(bird.cX > pipe.cX & bird.cY < pipe.cY-10 ){
if(bird.cX < pipe.cX+pipe.width){
cancelAnimationFrame(timer1)
this.gameOver();
}
}else if(bird.cX > pipe.cX & bird.cY+bird.px > pipe.cY+gapHeight+10){
if(bird.cX < pipe.cX+pipe.width){
cancelAnimationFrame(timer1)
this.gameOver();
}

}

},
```

```// 根据小鸟x坐标和管道宽度进行判断   每完成一次就加1
if(pipe.x ==10){
bnum+=1;
console.log(bnum)
this.setData({
bird_number:bnum
})
}
```