Canvas gradient fill in Chrome works in IE 11 freezes, how to win?

S

sozercanie_kosmosa2018-12-29 22:19:56

JavaScript

sozercanie_kosmosa, 2018-12-29 22:19:56

Everything works in Chorme, but IE 11 slows down a lot.
How to overcome this programmatically without resorting to creating a gradient through the image.
Only software.
About IE:

Here is the code ( link to fiddle ):

<html><head></head><body><script>
let sz = 80;
let cnv = createCanvasSize(sz,sz);
createGragientSL(cnv.ctx, sz, sz);
document.body.appendChild(cnv);

function createGragientSL(ctx, w, h) {
    const accur = w;
    const wCol = w / accur;

    let grd = ctx.createLinearGradient(0, 0, 0, h);

    for (let i = 0; i <= accur - 1; i++) {
        let alpha = 1 - 1 / accur * i;
        let colorA = 'rgba(255,255,255,' + alpha + ')';
        grd.addColorStop(0, colorA);
        let colorB = 'rgba(0,0,0,' + alpha + ')';
        grd.addColorStop(1, colorB);

        ctx.fillStyle = grd;
        ctx.fillRect(wCol * i, 0, (wCol), h);
    }
}

function createCanvasSize(width, height, className) {
    let node = document.createElement('canvas');
    if (className) node.classList.add(className);
    node.width = width;
    node.height = height;
    node.ctx = node.getContext('2d');
    return node;
}
</script></body></html>

Reply

Answer the question

In order to leave comments, you need to log in

1 answer(s)

G

grinat, 2018-12-29
@sozercanie_kosmosa

Do it through Uint8ClampedArray and manually set colors and transparency there, then insert it. What you wrote will slow down always and everywhere:

let ctx = canvas.getContext('2d')
 let data = ctx.createImageData(screenWidth, screenHeight)
 for (var i = 0; i < data.length; i += 4) {
      data[i] =  // red
      data[i + 1] = // green
      data[i + 2] =  // blue
      data[i + 3] = // opacity
   }
   ctx.putImageData(data, 0, 0)