javascript - 使用 base64 编码/解码图像会破坏图像

Question

我正在尝试对图像进行编码和解码。我正在使用 FileReader 的 readAsDataURL 方法将图像转换为 base64。然后将其转换回来，我尝试使用 readAsBinaryString() 和 atob() 但没有成功。有没有另一种方法可以在不使用 base64 编码的情况下保留图像？

readAsBinaryString()

Starts reading the contents of the specified Blob, which may be a File. When the read operation is finished, the readyState will become DONE, and the onloadend callback, if any, will be called. At that time, the result attribute contains the raw binary data from the file.

知道我在这里做错了什么吗？

示例代码 http://jsfiddle.net/qL86Z/3/

$("#base64Button").on("click", function () {
    var file = $("#base64File")[0].files[0]
    var reader = new FileReader();

    // callback for readAsDataURL
    reader.onload = function (encodedFile) {
        console.log("reader.onload");
        var base64Image = encodedFile.srcElement.result.split("data:image/jpeg;base64,")[1];
        var blob = new Blob([base64Image],{type:"image/jpeg"});
        var reader2 = new FileReader();

        // callback for readAsBinaryString
        reader2.onloadend = function(decoded) {
            console.log("reader2.onloadend");
            console.log(decoded); // this should contain binary format of the image

            // console.log(URL.createObjectURL(decoded.binary)); // Doesn't work
        };
        reader2.readAsBinaryString(blob);

        // console.log(URL.createObjectURL(atob(base64Image))); // Doesn't work

    };
    reader.readAsDataURL(file);
    console.log(URL.createObjectURL(file)); // Works
});

谢谢!

Answer 1

经过更多研究，我从 here 找到了答案我基本上需要将原始二进制文件包装在数组缓冲区中并将二进制字符转换为 Unicode。

这是丢失的代码，

    var binaryImg = atob(base64Image);
    var length = binaryImg.length;
    var ab = new ArrayBuffer(length);
    var ua = new Uint8Array(ab);
    for (var i = 0; i < length; i++) {
        ua[i] = binaryImg.charCodeAt(i);
    }

完整的示例代码是here