使用javascript来互相转换画布canvas和图片image
1.使用javascript的drawImage方法可以方便的将图片image转换为画布canvas，如下
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// Converts image to canvas; returns new canvas element
function convertImageToCanvas(image) {
var canvas = document.createElement("canvas");
canvas.width = image.width;
canvas.height = image.height;
canvas.getContext("2d").drawImage(image, 0, 0);
return canvas;
}
2.同时也可以用以下代码来将画布canvas转化为图片image，如下：
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// Converts canvas to an image
function convertCanvasToImage(canvas) {
var image = new Image();
image.src = canvas.toDataURL("image/png");
return image;
}
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