如何检查画布是否为空白？ [英] How to check if a canvas is blank?

问题描述

如果HTML5画布为空白或有彩色像素，我该如何检查。是否有快速方法？

How can I check, if a HTML5 canvas is blank or has colored pixels. Is there a fast method?

<canvas width="200" height="200"></canvas>

推荐答案

您可以创建一个新的空白画布， URL等。

You can create a new blank canvas, and compare data URLs like so.

function isCanvasBlank(canvas) {
    var blank = document.createElement('canvas');
    blank.width = canvas.width;
    blank.height = canvas.height;

    return canvas.toDataURL() == blank.toDataURL();
}

JSFiddle

JSFiddle

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