function b64ToUint8Array(b64Image) {
var img = atob(b64Image.split(',')[1]);
var img_buffer = [];
var i = 0;
while (i < img.length) {
img_buffer.push(img.charCodeAt(i));
i++;
}
return new Uint8Array(img_buffer);
}
var b64Image = canvas.toDataURL('image/jpeg');
var u8Image = b64ToUint8Array(b64Image);
var formData = new FormData();
formData.append("image", new Blob([ u8Image ], {type: "image/jpg"}));
var xhr = new XMLHttpRequest();
xhr.open("POST", "/api/upload", true);
xhr.send(formData);
用上面这种方式在前端通过js处理，server端不需要进行任何额外处理。
我认为是最方便最直接的办法，反而很多高赞回复，需要server进行各种处理，不推荐。
Had to convert canvas Base64-encoded image to Uint8Array Blob.
