如何将图片显示为canvas
https://github.com/blueimp/JavaScript-Load-Image/blob/master/js/load-image-scale.js
https://github.com/blueimp/JavaScript-Load-Image/blob/master/js/load-image-scale.js#L106
// Determines if the target image should be a canvas element: loadImage.hasCanvasOption = function (options) { return options.canvas || options.crop || !!options.aspectRatio }
原文：https://www.cnblogs.com/chucklu/p/11133905.html