在 C# 中将 base64 转换为图像

Question

I am using MVC#. When i try To convert to base64 string to image, the image is not getting opened. I am getting base64 string from javascript and coverting that to image in controller. Here's my code.

var base64 = "data:image/png;base64,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...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";

byte[] str = System.Text.Encoding.Unicode.GetBytes(base64);
var buffer = Convert.FromBase64String(Convert.ToBase64String(str));
var file = Server.MapPath("~/Content/images/err.png");
System.IO.File.WriteAllBytes(file, buffer);
Image img = new Image();
img.ImageUrl = Server.MapPath("~/Content/images/err.png");

Answer 1

Your code is totally wrong.

You need to parse out the actual base64 data from that string, by removing everything before the first comma.

You can then call Convert.FromBase64String() on that data.

string source = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAABG4...YII=";
string base64 = source.Substring(source.IndexOf(',') + 1);
byte[] data = Convert.FromBase64String(base64);

Answer 2

I copied that base64 string prompt window. I used ajax method for posting the base64 string from client and it works for me

C#

[HttpPost]
public void Base64ToImage(string source)
{
    string base64 = source.Substring(source.IndexOf(',') + 1);
    base64 = base64.Trim('\0');
    byte[] chartData = Convert.FromBase64String(base64);
}

AJAX Method

var picture = jqplotToImg($('#ChartContent'));
//prompt("", picture);

$.ajax({ type: 'POST',
    url: '../Report/Base64ToImage',
    async: false,
    data: { source: picture },
    success: function (data) {
        //alert(data);
    }
});