Cropping 2 images

Question

Hello! I saw a lot of posts like that, but i can't solce my problem :(

My app shoud load a photo from the camera and put it into a 450*600 Image (called imgOrig).

After that, the app should create 2 little images cropped from imgOrig like these 2 red squares:

I can't solce this boring problem... Every piece of code i write doesn't work... Can you help me please?

I wrote this:

img1.Clip = new RectangleGeometry() { Rect = new Rect(0, 0, 150, 150) };

img2.Clip = new RectangleGeometry() { Rect = new Rect(150, 0, 150, 150) };

The first instruction works fine. The second shows nothing.

Both of them had a width and height of 150px and a Source property set on imgOrig.Source

Can anyone help me? I'm crying :(

Thank you and sorry for my bad english... Greets from Italy :)

Sergio

Answer 1

Hi Sergio,

Your app can load a cropped version of the bitmap from the StorageFile returned by the CameraCaptureUI by opening the file into a stream and then running it through a BitmapDecoder with a BitmapTransform set to crop to the 150x150 sub-images:

            IRandomAccessStream stream = await img.OpenReadAsync();
            // Set the original full sized image
            BitmapImage bmp = new BitmapImage();
            bmp.SetSource(stream);
            originalImage.Source = bmp;

            // Go back to the beginning and set up a bitmapDecoder
            stream.Seek(0);
            BitmapDecoder decoder = await BitmapDecoder.CreateAsync(stream);
            
            // With our cropping BitmapTransform
            BitmapTransform transform = new BitmapTransform();
            BitmapBounds bounds = new BitmapBounds();
            bounds.X = bounds.Y = 0;
            bounds.Height = bounds.Width = 150;
            transform.Bounds = bounds;

            // Get the cropped pixels
            PixelDataProvider pix = await decoder.GetPixelDataAsync(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Straight, transform, ExifOrientationMode.RespectExifOrientation, ColorManagementMode.ColorManageToSRgb);
            byte[] pixels = pix.DetachPixelData();

            // And stream them into a WriteableBitmap
            WriteableBitmap cropBmp = new WriteableBitmap(150, 150);
            Stream pixStream = cropBmp.PixelBuffer.AsStream();
            pixStream.Write(pixels, 0, 150 * 150 * 4);
            // Which we set on our first cropped Image
            crop1.Source = cropBmp;

            // Then move the crop to the second location
            bounds.X = 150;
            transform.Bounds = bounds;

            // And decode again
            pix = await decoder.GetPixelDataAsync(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Straight, transform, ExifOrientationMode.RespectExifOrientation, ColorManagementMode.ColorManageToSRgb);
            pixels = pix.DetachPixelData();
            cropBmp = new WriteableBitmap(150, 150);
            pixStream = cropBmp.PixelBuffer.AsStream();
            pixStream.Write(pixels, 0, 150 * 150 * 4);
           
            // Then set to the second cropped image
            crop2.Source = cropBmp;

--Rob

Answer 2

Hi Rob!

First, i would like to thank you for your answer and the time you spend on my problem :) You're great! However, I copied your code, but Visual Studio returned me 2 errors...

Error 1 'Windows.Storage.Streams.IBuffer' does not contain a definition for 'AsStream' and the best extension method overload 'System.IO.WindowsRuntimeStreamExtensions.AsStream(Windows.Storage.Streams.IRandomAccessStream)' has some invalid arguments C:\Users\Sergio\Desktop\MyApp\MyApp\MainPage.xaml.cs 98 36 MyApp

Error 2 'Windows.Storage.Streams.IBuffer' does not contain a definition for 'AsStream' and the best extension method overload 'System.IO.WindowsRuntimeStreamExtensions.AsStream(Windows.Storage.Streams.IRandomAccessStream)' has some invalid arguments C:\Users\Sergio\Desktop\MyApp\MyApp\MainPage.xaml.cs 111 29 MyApp

The error is under

Stream pixStream = cropBmp.PixelBuffer.AsStream();

and

 pixStream = cropBmp.PixelBuffer.AsStream();

instructions.

Any ideas?

Thank you very much!

Sergio

---

Sergio Meloni

Answer 3

Hi Sergio,

AsStream is an extension method, so you need to include the appropriate "using" statement:

using System.Runtime.InteropServices.WindowsRuntime;

You can figure this out by going to the object browser, searching on AsStream, and looking to see which namespace it is defined in.

--Rob

Answer 4

OMG, You saved my work! If I'll ever come to USA, I absolutely have to offer you a coffee!!

Thank you very much!

Sergio

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Sergio Meloni