How use the Byte Array of a image?

Question

So, i am getting the byte array of a LongRaw image from Oracle... I am using a webapi to this. After get the array, how i use it on the Client-side ? Do Its better i convert to base64string and pass this value converting just at the client side ?

cmd.InitialLONGFetchSize = -1;
                var reader = cmd.ExecuteReader();

                if (reader.Read())
                {
                    // Fetch the LONG RAW
                    OracleBinary imgBinary = reader.GetOracleBinary(0);
                    // Get the bytes from the binary obj
                    byte[] imgBytes = imgBinary.IsNull ? null : imgBinary.Value;

                    //var imgString = Uri.EscapeDataString(Convert.ToBase64String(imgBytes));
                }

                //CRIO A LISTA
                lretorno.Load(reader, LoadOption.OverwriteChanges, "BUSCAFOTO");

                reader.Close();

                connection.Close();
                connection.Dispose();

                var teste = lretorno.Tables[0].AsEnumerable().Select(row => new FotoEnvolvido
                {
                    FOTO = (byte[])(row["FOTO"]),
                    //FOTO = Convert.ToString(row["FOTO"]),
                });

                return teste;

Ralf Bönning · Accepted Answer · 2016-09-09 15:18:37Z

2

You can write a Web API Controller that returns the binary data of an image. Base64 strings impose a overhead of the amount of bytes that have to be transmitted. Please avoid this.

A sample controller can look like this example:

public class WebApiController : ApiController
{        
    public async Task<HttpResponseMessage> Get(string id)
    {
        var bytes = await GetBytesFromDataLayerAsync(id);

        HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);
        var stream = new MemoryStream(bytes);
        result.Content = new StreamContent(stream);
        result.Content.Headers.ContentType =
            new MediaTypeHeaderValue("image/jpeg");
        return result;
    }

    private async Task<byte[]> GetBytesFromDataLayerAsync(string id)
    {
        // put your Oracle logic here
        return ...
    }
}

answered Sep 9, 2016 at 15:18

Ralf Bönning

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6 Comments

Mcfer Over a year ago

I need to encrypt the content of my Json´s... i did this to all strings...But, now with these ByteArray, i think its better i convert before pass the image, is not ??

Mcfer Over a year ago

Your code worked fine my friend...many thanks !! I just have the other question..

Ralf Bönning Over a year ago

Why do you need to encrypt the content of your JSONs? Normally they are protected by SSL/TLS.... https... - But if you have another question regarding encryption/decryption you should post a new question on SO.

Mcfer Over a year ago

Oh men... i don´t know !! I just know that i need...lol I already told to them, but the security department are not normal

Ralf Bönning Over a year ago

Oh dear - I cannot even imagine a solution. The browser has to decrypt the JSON data (this could be done by transferring an encrypted Json-String + encryption on the JavaScript side (this code can be accessed by anyone). Perhaps there are some good JavaScript libraries. But this is a whole new topic (and another post). Good Luck!

|

Community · Accepted Answer · 2017-05-23 12:24:21Z

1

Depending on what your doing as rboe said writing the bytes directly to the client will save some data size(approx. 37%) and computing overhead. If your not only displaying jpeg images you should also set the mime-type to the correct value... take a look at this source for a rather complete set of extension to mime-type mappings. If you do not know the mime-type you can try "application/octet-stream" as that is the general mime-type for binary data.

If your displaying your content via web browser you could just use an <img> tag something like <img src="view_image.aspx?id=5"> you can even create the dynamically with javascript/jQuery.

If you really do want the image data embedded in a json request which might be useful if you have a lot of little icons and don't want a ton of requests (with http/2 I don't think this will matter) or another reason, then yes first encode the binary data using...

string base64EncodedData = Convert.ToBase64String(bytes);

If the client is javascript you can decode using the latest browsers native functions

var decodedImageData = window.atob(base64EncodedData);

See:

If you are however just sending it to another c# endpoint you can use...

byte[] decodedImageData = Convert.FromBase64String(base64EncodedData);

And like I mentioned in the comment to ensure it's encrypted just make the site only support https:// and if you don't have a SSL cert you can get one for free from http://startssl.com

edited May 23, 2017 at 12:24

CommunityBot

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answered Sep 10, 2016 at 3:29

xer21

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2 Comments

Mcfer Over a year ago

My friend...thanks for the explanation !! Awsome.... But, i already told to everybody here in my job about this (ssl "encrypt") and doesnt matter... all the protocols are over HTTPS, but they still need that i encrypt the datas. Oh, i am using xamarin c# to catch the datas from web api.

xer21 Over a year ago

@MarceloCFernandes Since you still needed help with encryption, I looked up your other encrypt json question and posted an answer on there. You can use the same code basically for encrypting the image in addition to the json See: stackoverflow.com/questions/38962083/… please mark as answer if it works out for you.

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