html 背景边缘模糊,如何修复HTML5画布中的模糊形状边缘？

var aWrapper = document.getElementById("aWrapper");

var canvas = document.getElementById("myCanvas");

//Accesses the 2D rendering context for our canvasdfdf

var ctx = canvas.getContext("2d");

function setCanvasScalingFactor() {

return window.devicePixelRatio || 1;

}

function resizeCanvas() {

//Gets the devicePixelRatio

var pixelRatio = setCanvasScalingFactor();

//The viewport is in portrait mode, so var width should be based off viewport WIDTH

if (window.innerHeight > window.innerWidth) {

//Makes the canvas 100% of the viewport width

var width = Math.round(1.0 * window.innerWidth);

}

//The viewport is in landscape mode, so var width should be based off viewport HEIGHT

else {

//Makes the canvas 100% of the viewport height

var width = Math.round(1.0 * window.innerHeight);

}

//This is done in order to maintain the 1:1 aspect ratio, adjust as needed

var height = width;

//This will be used to downscale the canvas element when devicePixelRatio > 1

aWrapper.style.width = width + "px";

aWrapper.style.height = height + "px";

canvas.width = width * pixelRatio;

canvas.height = height * pixelRatio;

}

var cascadeFactor = 255;

var cascadeCoefficient = 1;

function draw() {

//The number of color block columns and rows

var columns = 5;

var rows = 5;

//The length of each square

var length = Math.round(canvas.width/columns) - 2;

//Increments or decrements cascadeFactor by 1, based on cascadeCoefficient

cascadeFactor += cascadeCoefficient;

//Makes sure the canvas is clean at the beginning of a frame

ctx.clearRect(0, 0, canvas.width, canvas.height);

for (var i = columns; i >= 1; i--) {

for (var j = rows; j >= 1; j--) {

//Where the color magic happens

ctx.fillStyle = "rgba(" + (j*i*(cascadeFactor-110)) + "," + (i*cascadeFactor) + "," + (j*cascadeFactor) + "," + 0.6 + ")";

ctx.fillRect((length*(i-1)) + ((i-1)*2), (length*(j-1)) + ((j-1)*2), length, length);

}

}

if (cascadeFactor > 255 || cascadeFactor < 0) {

//Resets the color cascade

cascadeCoefficient = -cascadeCoefficient;

}

//Continuously calls draw() again until cancelled

var aRequest = window.requestAnimationFrame(draw);

}

window.addEventListener("resize", resizeCanvas, false);

resizeCanvas();

draw();

#aWrapper {

margin: 0 auto;

}

#myCanvas {

display: block;

width: 100%;

height: 100%;

}

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