javascript - 为什么更改 Canvas 大小会重置其参数？

Question

当我更改 Canvas 大小时，我注意到参数“mozImageSmoothingEnabled”被重置。

HTML

<canvas id='canv'>Your browser don't support canvas.</canvas>

Javascript

var cnv = document.getElementById('canv');
var ctx = cnv.getContext('2d');
console.log(ctx.mozImageSmoothingEnabled); // default 'true'
ctx.mozImageSmoothingEnabled = false;
console.log(ctx.mozImageSmoothingEnabled); // shows 'false'
cnv.width = 100;
console.log(ctx.mozImageSmoothingEnabled); // shows 'true'

JSFiddle:https://jsfiddle.net/epvtuz37/

这是一个错误，还是预期的行为？

Answer 1

因为当您更改 Canvas 宽度或高度参数时，附加上下文的每个属性都会重置为其默认值。

From specs

When the canvas element is created, and subsequently whenever the width and height attributes are set (whether to a new value or to the previous value), the bitmap and any associated contexts must be cleared back to their initial state and reinitialized with the newly specified coordinate space dimensions.