Use Canvas to achieve the bubble effect of likes during live broadcast-Mini Program Development-php.cn

Use Canvas to achieve the bubble effect of likes during live broadcast

巴扎黑

Release： 2017-09-12 10:05:33

Original

3071 people have browsed it

Firstly send Canvas to implement the live broadcast like bubble effect diagram:

Implementation details:

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}]]) 
     }) 
    }}

Copy after login

2. Principle:

a. By drawing three different third-order Bezier curves, select three pictures and let them move along their respective Bezier curves. The movement trajectories are as follows:

b. Calculate the mathematical expression of third-order Bezier curve x(t), y(t).

The third-order Bezier curve forms a curve through four points, two control points, a starting point and an end point.

The mathematical expressions of x(t), y(t) can be obtained by using polynomial coefficients:
cx = 3 * (x1 - x0)bx = 3 * (x2 - x1) - cxax = x3 - x0 - cx - bxcy = 3 * ( y1 - y0 ) by = 3 * ( y2 - y1 ) - cyay = y3 - y0 - cy - byx(t) = ax * t ^ 3 + bx * t ^ 2 + cx * t + x0y(t) = ay * t ^ 3 + by * t ^ 2 + cy * t + y0
Three Bezier curves are drawn here. Just apply the formula three times. No loop is used here. If When there are many Bezier curves, you can call ctx.drawImage in a loop, where factor.t is the parameter of the third-order Bezier curve, with a value range of [0,1], and finally call ctx.draw(), and set The timer can realize the movement of the picture along the Bezier curve.
3.Tip:

The timer used here is implemented through the requestAnimationFrame() function. The reason for deprecating setInterval is that there is a frame stuck phenomenon in the actual test and the animation display is slightly discontinuous.

The above is the detailed content of Use Canvas to achieve the bubble effect of likes during live broadcast. For more information, please follow other related articles on the PHP Chinese website!