BitmapImage to byte array and vice versa

Question

I am developing an image processing app in uwp windows 10. I am opening an image using file picker as shown below.

FileOpenPicker openPicker = new FileOpenPicker();           
           openPicker.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
           openPicker.ViewMode = PickerViewMode.Thumbnail;
           openPicker.FileTypeFilter.Clear();
           openPicker.FileTypeFilter.Add(".bmp");
           openPicker.FileTypeFilter.Add(".png");
           openPicker.FileTypeFilter.Add(".jpeg");
           openPicker.FileTypeFilter.Add(".jpg");
           StorageFile file = await openPicker.PickSingleFileAsync();
            if(file!=null)
            {
                IRandomAccessStream fileStream = await file.OpenAsync(FileAccessMode.Read);
                BitmapImage bitmapImage = new BitmapImage();
                bitmapImage.SetSource(fileStream);
                myImage.Source = bitmapImage;

                // code to retrieve bytes of bitmap image
            }

Inside above if statement, I am retrieving bytes from this image like shown below.

//Fetching pixel data
            using (IRandomAccessStream fileStreams = await file.OpenAsync(Windows.Storage.FileAccessMode.Read))
            {
                BitmapDecoder decoder = await BitmapDecoder.CreateAsync(fileStreams);
                BitmapTransform transform = new BitmapTransform()
                {
                    ScaledWidth = Convert.ToUInt32(bitmapImage.PixelWidth),
                    ScaledHeight = Convert.ToUInt32(bitmapImage.PixelHeight)
                };
                PixelDataProvider pixelData = await decoder.GetPixelDataAsync(
                    BitmapPixelFormat.Rgba8,
                    BitmapAlphaMode.Straight,
                    transform,
                    ExifOrientationMode.IgnoreExifOrientation,// This sample ignores Exif orientation
                    ColorManagementMode.DoNotColorManage
               );

                // byte[] , a global variable
                sourcePixels = pixelData.DetachPixelData();
                // uint , a global variable
                width = decoder.PixelWidth;
                // uint , a global variable
                height = decoder.PixelHeight;
            }

Now I need to manipulate this byte array for generating different effects. But for testing purpose, I am converting this byte array, again to bitmapimage and setting its value to main image source (in button click event). but it is not working correctly as

 WriteableBitmap scaledImage = new WriteableBitmap((int)width, (int)height);
            using (Stream stream = scaledImage.PixelBuffer.AsStream())
            {
                await stream.WriteAsync(sourcePixels, 0, sourcePixels.Length);
                myImage.Source = scaledImage;
            }

when the image was opened, it was like this.

when applied again after changing it to byte array and byte array to image source. It changes the image colors, although i haven't changed any values of byte array.

Where is the problem?? Whether the conversion to byte array is wrong or conversion of byte array to bitmap?

Answer 1

Solution:

Well, I have found the solution of this issue, it was that I was using BitmapPixelFormat.Rgba8 in PixelDataProvider (while fetching pixels data). Rather I should use BitmapPixelFormat. Bgra8 .