Run results for: Canvas clearing performance v3

Test name	Executions per second
✓ Clear only	41,164 Ops/sec
Save transform Clear restore	37,086 Ops/sec
fillRect	35,130 Ops/sec
w=w	31,936 Ops/sec
w+=0	29,492 Ops/sec
Canvas w with memo	17,410 Ops/sec
createImageData	260 Ops/sec

Script Preparation code:

var canvasOne = document.getElementById("canvasOne");
var ctx = canvasOne.getContext("2d", {desynchronized: true, alpha: true, preserveDrawingBuffer: true});

var canvasTwo = document.getElementById("canvasTwo");
var ctxTwo = canvasTwo.getContext("2d");

var canvasThree = document.getElementById("canvasThree");
var ctxThree = canvasThree.getContext("2d");

var canvasFour = document.getElementById("canvasFour");
var ctxFour = canvasFour.getContext("2d");

Tests:

Clear only
ctx.fillStyle = 'rgba(255, 255, 255, 0.3)'; ctx.fillRect(0, 0, 400, 400); ctx.clearRect(0,0,ctx.canvas.width,ctx.canvas.height); ctx.beginPath(); ctx.fillStyle = 'rgba(231, 76, 60, 0.1)'; ctx.arc(200, 200, 100, 0, Math.PI * 2, true); ctx.fill();
Save transform Clear restore
ctx.fillStyle = 'rgba(255, 255, 255, 0.3)'; ctx.fillRect(0, 0, 400, 400); ctx.save(); ctx.setTransform(1,0,0,1,0,0); ctx.clearRect(0,0,ctx.canvas.width,ctx.canvas.height); ctx.restore(); ctx.beginPath(); ctx.fillStyle = 'rgba(231, 76, 60, 0.1)'; ctx.arc(200, 200, 100, 0, Math.PI * 2, true); ctx.fill();
Canvas w with memo
ctx.fillStyle = 'rgba(255, 255, 255, 0.3)'; ctx.fillRect(0, 0, 400, 400); var w = ctx.canvas.width; ctx.canvas.width = 1; ctx.canvas.width = w; ctx.beginPath(); ctx.fillStyle = 'rgba(231, 76, 60, 0.1)'; ctx.arc(200, 200, 100, 0, Math.PI * 2, true); ctx.fill();
w=w
ctx.fillStyle = 'rgba(255, 255, 255, 0.3)'; ctx.fillRect(0, 0, 400, 400); ctx.canvas.width = ctx.canvas.width; ctx.beginPath(); ctx.fillStyle = 'rgba(231, 76, 60, 0.1)'; ctx.arc(200, 200, 100, 0, Math.PI * 2, true); ctx.fill();
w+=0
ctx.fillStyle = 'rgba(255, 255, 255, 0.3)'; ctx.fillRect(0, 0, 400, 400); ctx.canvas.width += 0; ctx.beginPath(); ctx.fillStyle = 'rgba(231, 76, 60, 0.1)'; ctx.arc(200, 200, 100, 0, Math.PI * 2, true); ctx.fill();
fillRect
ctx.fillStyle = 'rgba(255, 255, 255, 0.3)'; ctx.fillRect(0, 0, 400, 400); ctx.fillStyle = 'rgba(0, 0, 0, 1)'; ctx.fillRect(0,0,ctx.canvas.width, ctx.canvas.height); ctx.beginPath(); ctx.fillStyle = 'rgba(231, 76, 60, 0.1)'; ctx.arc(200, 200, 100, 0, Math.PI * 2, true); ctx.fill();
createImageData
ctx.fillStyle = 'rgba(255, 255, 255, 0.3)'; ctx.fillRect(0, 0, 400, 400); var i = ctx.createImageData(ctx.canvas.width, ctx.canvas.height); ctx.putImageData(i, 0, 0); // clear context by putting empty image data ctx.beginPath(); ctx.fillStyle = 'rgba(231, 76, 60, 0.1)'; ctx.arc(200, 200, 100, 0, Math.PI * 2, true); ctx.fill();

Run results for: Canvas clearing performance v3

https://stackoverflow.com/questions/2142535/how-to-clear-the-canvas-for-redrawing

Clear only

Save transform Clear restore

Canvas w with memo

w=w

w+=0

fillRect

createImageData