Retrieving Data URI from an image added via the "Add picture" control

[df]

I am trying to submit a photo taken from a PowerApps app to a custom API. There are a number of tutorials written for it, but they all use the built-in camera control, which is very limiting as far as photo-taking goes. It seems that the recent addition of native camera functionality (https://powerapps.microsoft.com/en-us/blog/powerapps-v610/) should work much better, however I am struggling with obtaining the image data from the "Add picture" control.

The problem narrows down to the following: when you obtain image data from the Camera control (using the Camera1.Photo property) you get a long Data URI string containing the actual image, it like this:

data&colon;image/jpeg;base64<long base64 string follows>

When I obtain the image from the "Add picture" control (using AddMediaButton1.Media property) I get a string that looks like this:

blob:https://us.create.powerapps.com/dd6409a9-1b09-4ef5-a64b-21c84b16bb54 (if using the web player)
blob:http://127.0.0.1:49428/b7371d5a-bec9-45da-acb4-e2c6a1fefff6 (if using the Android player)

So it seems that instead of the actual image content I am getting some kind of a reference to a local blob storage, which is of no use for the purposes of passing it to the API that is expecting the actual image.

QUESTION: how can I obtain a proper Data URI string containing the actual image from the "Add picture" control?

[v-micsh-msft]

Hi @df,

Currently I have no idea about this.

And just as you mentioned, the Add picture only gives the corresponding blob storage information, there is no property could be referenced to get the proper base64 data.

I will forward this from my side, and will update here if I got any helpful response.

You may consider to submit an idea for this, to suggest Add picture control offer a property for the base64 data.

https://powerusers.microsoft.com/t5/PowerApps-Ideas/idb-p/PowerAppsIdeas

Regards,

Michael

[df]

Thank you Michael.

Yes, I would appreciate if you could get more information on this. It really feels that there shouldb be a way to obtain actual image data from the control since otherwise it is not clear what application scenario this control is at all useful for.

[claudiosvcc]

Hi, it seems there's a workaround you might try. There are other teams using custom APIs with add picture and that's working for them:

Instead of trying to send the AddMediaButton1.Media property directly, add an Image object (Say Image1), assign AddMediaButton1.Media to it and then use this Object on your custom API Image1.Image

You might want to hide this second image.

[df]

Hi claudiosvcc,

I tried that, but unfortunately I am still getting a blob pointer on both the Web and the Android players. Have you personally been able to make it work? 

Thanks!

[claudiosvcc]

Hi,

Sorry for taking that long to answer, but we were investigating more here.

So, yes we can make it work (We don't even need that other image hack - from the addPicture media directly it also works). But please, don't expect that instead of seeing a blob address on a text field you would see a base64 value. That won't happen. This is done during the connection.

So, why yours is not working, I can't tell for now. But my guess it's probably related with the CustomAPI you're using. Somehow your customAPI is communicating wrongly with the connector and this is making it send a text instead of having the image bits.

Can you please share a snippet of your image upload custom API so we can take a look and try to find the issue?

In either case, this is a bug anyway. We're currently tracking it in another similar bug we have.

[df]

Thanks claudiosvcc. Good to know that a bug fix is in the works. When can we expect it to be released?

This is the custom API code that is handling the saving of the image, it works great with the "Camera" control, but doesn't work at all with the "Add picture" control due to the fact that the latter passes a blob pointer rather than a base64 string:

[HttpPost]
public IHttpActionResult UploadFile([FromBody]string dataUri)
{
    var filename = @"c:\webapilog\" + Guid.NewGuid() + ".jpg";
    var base64Data = Regex.Match(dataUri, @"data&colon;image/(?<type>.+?),(?<data>.+)").Groups["data"].Value;
    var binData = Convert.FromBase64String(base64Data);

    File.WriteAllBytes(filename, binData);

    return Ok(filename);
}

To clarify -- are you saying that there already is a way to make "Add picture" work, even before the bug fix is released? It looked like in your response you implied that there already is a way to configure Custom API to accept image data from "Add picture" control, but I am not sure.

[claudiosvcc]

"are you saying that there already is a way to make "Add picture" work, even before the bug fix is released?"

yes.

First of all, thanks for your snippet. That helped us to identify why this can be working the wrong way. Seems your API is expecting a string. While on Camera control they grab the stream generated by camera, on AddPicture control, the only string they have is the blob address. 

In this snippet I'm sending below, that should work for both Camera and AddPicture control, because server side is now expecting a File and the CustomAPI knows where that can be found on the AddPicture control.

This sample is using ASP.Net Core, but that should be similar for WebApi2.

In this snippet below, it's expecting a FILE and returning the filename and file size.

Hope it helps. Please let me know if you find any issues.

public class ImageUploadResponse
    {
        public string FileName { get; set; }
        public Int64 Size { get; set; }
    }

    [Route("api/[controller]")]
    public class ImageUploadController : Controller
    {
        
[HttpPost]
        public async Task<ImageUploadResponse> UploadPost(IFormFile file)
        {
            var res = new ImageUploadResponse { FileName = file.FileName, Size = file.Length };
            return await Task.FromResult(res);            
        }
    }

[df · Accepted solution]

Thank you! Your last response actually helped me arrive to a working solution. In case anyone else is struggling with the same issue, I am posting my working Web API 2 code here. In my use case, the uploaded image needs to be tagged with an entityId and uploaded to Sharepoint (I am not including the Sharepoint upload code here):

        public async Task<IHttpActionResult> UploadImage(int entityId)
        {
            const string storagePath = @"C:\temp";
            var result = false;

            try
            {
                // Check if the request contains multipart/form-data.
                if (!Request.Content.IsMimeMultipartContent())
                    throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);

                var provider = new MultipartFormDataStreamProvider(storagePath);

                // Read the form data.
                await Request.Content.ReadAsMultipartAsync(provider);

                // This illustrates how to get the file names.
                var fileData = provider.FileData[0];
                if (string.IsNullOrEmpty(fileData.Headers.ContentDisposition.FileName))
                    throw new HttpResponseException(HttpStatusCode.InternalServerError);

                var fileName = fileData.Headers.ContentDisposition.FileName;
                fileName = fileName.Trim('"');

                var saveToPath = Path.Combine(storagePath, fileName);

                //temporarily save the file locally to be later uploaded to Sharepoint
                File.Move(fileData.LocalFileName, saveToPath);

                result = DataAccess.Sharepoint.UploadFile(entityId, saveToPath);

            }
            catch (Exception e)
            {
                return InternalServerError(e);
            }

            return Ok(result);

        }

The swagger for this method is as follows:

                "/Sharepoint/UploadImage": {
			"post": {
				"tags": [
					"Sharepoint"
				],
				"operationId": "UploadImage",
				"consumes": [
					"multipart/form-data"
				],
				"produces": [
					"application/json",
					"text/json",
					"application/xml",
					"text/xml"
				],
				"parameters": [{
						"name": "file",
						"in": "formData",
						"required": true,
						"type": "file",
						"x-ms-media-kind": "image"
					}, {
						"name": "entityId",
						"in": "query",
						"required": false,
						"type": "integer"
					}
				],
				"responses": {
					"200": {
						"description": "OK",
						"schema": {
							"type": "object"
						}
					}
				},
				"description": "Upload image via form post",
				"summary": "Upload image"
			}
		}

The API is then called from a button in my PowerApp as follows:

MyCustomAPI.UploadImage(AddMediaButton2.Media, {entityId: 251})

Hope this helps someone out. 

Thanks again claudiosvcc!

[codjangmah]

Hello I was trying to replicate your code but its not working for me.
I tried to create an Azure WebAPI function but getting lots of errors. Can you confirm the namespaces and nuget packages you are using.
 
public async Task<IHttpActionResult> UploadImage(int entityId)
        {
            const string storagePath = @"C:\temp";
            var result = false;

            try
            {
                // Check if the request contains multipart/form-data.
                if (!Request.Content.IsMimeMultipartContent())
                    throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);

                var provider = new MultipartFormDataStreamProvider(storagePath);

                // Read the form data.
                await Request.Content.ReadAsMultipartAsync(provider);

                // This illustrates how to get the file names.
                var fileData = provider.FileData[0];
                if (string.IsNullOrEmpty(fileData.Headers.ContentDisposition.FileName))
                    throw new HttpResponseException(HttpStatusCode.InternalServerError);

                var fileName = fileData.Headers.ContentDisposition.FileName;
                fileName = fileName.Trim('"');

                var saveToPath = Path.Combine(storagePath, fileName);

                //temporarily save the file locally to be later uploaded to Sharepoint
                File.Move(fileData.LocalFileName, saveToPath);

                result = DataAccess.Sharepoint.UploadFile(entityId, saveToPath);

            }
            catch (Exception e)
            {
                return InternalServerError(e);
            }

            return Ok(result);

        }