System.Convert.ToBase64String returning different result than the input to System.Convert.FromBase64String

Question

I'm writing a web application which saves images from the web to a database. Currently, what I use to save images is as follows:

[WebMethod]
public static void Save(string pictures)
{
    // pictures is an object containing the URL of the image along with some metadata
    List<ImageObject> imageList = new JavaScriptSerializer().Deserialize<List<ImageObject>>(pictures);
    for (int i = 0; i < imageList.Count; i++)
    {
        var webClient = new WebClient();
        byte[] byteArray = webClient.DownloadData(imageList[i].URL);
        imageList[i].Picture = byteArray;
    }
    // some SQL to save imageList
}

ImageObject:

[DataContract]
public class ImageObject
{
    [DataMember]
    public string URL { get; set; }
    [DataMember]
    public string Picture { get; set; }
}

Now, this works just fine for downloading from a URL. The entry saved to my database:

0xFFD8FFE000104A464946000101[...]331B7CCA7F0AD3A02DC8898F

To display this image, I simply callSystem.Convert.ToBase64String()after retrieving it and use it as an imagesrc. However, I am now trying to add some functionality for users to upload their own pictures. My function for this, called from an<input />:

function uploadPicture(){
    var numPics = document.getElementById("uploadedPictures").files.length;
    var oFReader = new FileReader();
    oFReader.onload = function (oFREvent) {
        var src = oFREvent.target.result;
        document.getElementById('image').src = src;
    }
    oFReader.readAsDataURL(document.getElementById("uploadedPictures").files.length;
}

When using this, this is the image source I get from the browser (over 2 MB when the original is only ~500 KB):

data:image/bmp;base64,/9j/4AAQSkZJRgABAgEAY[...]k8tTMZEBCsEbSeRYem493IHAfiHWq6vKlOv/Z

This gets displayed properly when used as a source. However, since this is not an actual URL (andWebClient.DownloadData()is restricted to URLs of < 260 characters), I have been trying other methods to save this data into my database. However, I cannot seem to find a function to save it in the same format asWebClient.DownloadData(). For example, I have looked at converting a base 64 string to an image and saving it, where most of the answers seem to useConvert.FromBase64String(), but using this appears to save in a different format to my database:

0x64006100740061003A0069006D0[...]10051004500420041005100450042004

Trying to useSystem.Convert.ToBase64String()on this returns

ZABhAHQAYQA6AGkAbQBhAGcAZQAvAGIAbQBwADsAYgBh[...]UwBlAFIAWQBlAG0ANAA5ADMASQBIAEEAZgBpAEgAVwBxADYAdgBLAGwATwB2AC8AWgA=

which is different from what I usedConvert.FromBase64String()on. Other things I found on Google to try and get it to save in the same format or display as an image have not worked thus far.

Hence, I am wondering whether there exists a method to convert the result from aFileReaderto the same format asWebClient.DownloadData()does for URLs or if there is some way to convert the0x6400[...]data to a format that can be displayed by using it as an<img>source.

score 0 · Accepted Answer · answered Oct 08 '13 at 14:58

It turns out that the reason the data saved into the database began with0x64006100[....]instead of0xFFD8FFE0[...]was due to me forgetting to strip the URI of the initialdata:image;base64,. After doing this, everything saves and is read properly usingSystem.Convert.ToBase64String().

System.Convert.ToBase64String returning different result than the input to System.Convert.FromBase64String

1 Answers1