在HTML中使用矩阵创建JS径向渐变

var canvas1 = document.getElementById("canvas"); //canvas1 variable to identify given canvas
var ctx1 = canvas.getContext("2d"); //This is used to tell context is 2D  

var gradient1 = ctx1.createRadialGradient(100/horizontalScale, 100/verticalScale, 100,
100/horizontalScale,100/verticalScale,0); //This will create gradient with given canvas context  

gradient1.addColorStop(1,"green"); //New color green is added to gradient
gradient1.addColorStop(0,"red"); //New color red is added to gradient

ctx1.scale(horizontalScale, verticalScale); //Context matrix ctx1 is shrinked according to horizaontal
and vertical scale
ctx1.fillStyle = gradient; //Given gradient is drawn
ctx1.fillRect(0,0, 100/horizontalScale, 100/verticalScale); //Rectangle is stretched according to scale
ctx1.setTransform(0,1,1,0,1,1);  //Context matrix is reset

canvas {    
   background-color: purple;
}
//Canvas is drawn with background color purple

<canvas id = "canvas" width = "300" height = "300"></canvas>