canvas与image互相转换

// Converts canvas to an image
function convertCanvasToImage(canvas) {
     var image = new Image();
     image.src = canvas.toDataURL("image/png");
     return image;
}

// 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;
}