HTML5 canvas drawing radioactive gradient color effect code example

This article mainly introduces the effect of drawing radioactive gradient colors on html5 canvas. Friends who need it can refer to it. I hope it can help everyone.

Rendering display:

There are still some pitfalls in canvas. For example, fillRect is a method, not an attribute. If you write fillRect=, it will have no effect. And no error is reported....

The createRadialGradient API is used here. This API receives 6 parameters. The first three represent the bottom circle, and the last three represent the upper circle. The returned instance can still be used with addColorStop.

can2_context is the canvas drawing context of getContext

function Radia(bottom_x,bottom_y,bottom_r,top_x,top_y,top_r){
  this.bottom_x=bottom_x;
  this.bottom_y=bottom_y;
  this.bottom_r=bottom_r;
  this.top_x=top_x;
  this.top_y=top_y;
  this.top_r=top_r;
  this.gradient=can2_context.createRadialGradient(this.bottom_x,this.bottom_y,this.bottom_r,this.top_x,this.top_y,this.top_r)
}
Radia.prototype.addColor=function(){
  for(var i=0;i<arguments.length;i++){
    this.gradient.addColorStop(arguments[i].num,arguments[i].color)
 }
}
Radia.prototype.draw=function(x1,y1,x2,y2){
   can2_context.fillStyle=this.gradient;
   can2_context.fillRect(x1,y1,x2,y2)
}
var some1=new Radia(canvas_2.width/2, canvas_2.height-100, 0, canvas_2.width/2, 0, 300)
some1.addColor({num:0.2,color:"blue"},{num:1,color:"yellow"},{num:0.7,color:"white"})
some1.draw(0, 0, canvas_2.width, canvas_2.height)

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