Creating a UWP desktop app in C# 4/5: Image composition - Combining background and photo

<Capabilities> <Capability Name="internetClient" /> <uap:Capability Name="picturesLibrary" /> </Capabilities>

using OpenCvSharp; using OpenCvSharp.Extensions; using System; using System.Collections.Generic; using System.IO; using System.Runtime.InteropServices; using System.Runtime.InteropServices.WindowsRuntime; using System.Threading.Tasks; using Windows.Media.Capture; using Windows.Storage; using Windows.UI.Xaml; using Windows.UI.Xaml.Controls; using Windows.UI.Xaml.Media.Imaging; namespace PhotoBooth { public sealed partial class MainPage : Page { private MediaCapture _mediaCapture; private bool _isPreviewing = true; public MainPage() { this.InitializeComponent(); EnterFullScreenMode(); InitializeCameraAsync(); } private void EnterFullScreenMode() { var view = Windows.UI.ViewManagement.ApplicationView.GetForCurrentView(); view.TryEnterFullScreenMode(); Windows.UI.ViewManagement.ApplicationView.PreferredLaunchWindowingMode = Windows.UI.ViewManagement.ApplicationViewWindowingMode.FullScreen; } private async void InitializeCameraAsync() { _mediaCapture = new MediaCapture(); await _mediaCapture.InitializeAsync(); CameraPreview.Source = _mediaCapture; await _mediaCapture.StartPreviewAsync(); } private async void CameraPreview_Tapped(object sender, Windows.UI.Xaml.Input.TappedRoutedEventArgs e) { if (_isPreviewing) { await StartCountdownAndTakePhoto(); } } private async Task StartCountdownAndTakePhoto() { try { CountdownText.Visibility = Visibility.Visible; for (int i = 2; i > 0; i--) { CountdownText.Text = i.ToString(); await Task.Delay(1000); } CountdownText.Visibility = Visibility.Collapsed; await TakePhotoAndCompositeWithOpenCVAsync(); } catch (Exception ex) { System.Diagnostics.Debug.WriteLine($"An error occurred in StartCountdownAndTakePhoto: {ex.Message}"); } } public static Mat WriteableBitmapToMat(WriteableBitmap wb) { // Get pixel data from WriteableBitmap as an array using (var stream = wb.PixelBuffer.AsStream()) { byte[] pixels = new byte[stream.Length]; stream.Read(pixels, 0, pixels.Length); // Create OpenCV Mat object (BGRA format) Mat mat = new Mat(wb.PixelHeight, wb.PixelWidth, MatType.CV_8UC4); // 8UC4: 8-bit unsigned 4-channel image (BGRA) // Copy WriteableBitmap's pixel data to Mat's memory buffer Marshal.Copy(pixels, 0, mat.Data, pixels.Length); return mat; } } public static WriteableBitmap MatToWriteableBitmap(Mat mat) { WriteableBitmap wb = new WriteableBitmap(mat.Width, mat.Height); using (Stream stream = wb.PixelBuffer.AsStream()) { byte[] pixels = new byte[mat.Width * mat.Height * mat.ElemSize()]; Marshal.Copy(mat.Data, pixels, 0, pixels.Length); stream.Write(pixels, 0, pixels.Length); } return wb; } private async Task<Mat> LoadAndResizeBackgroundImageAsync(StorageFile backgroundFile, int targetWidth, int targetHeight) { // Load background image Mat backgroundMat; using (Stream backgroundStream = await backgroundFile.OpenStreamForReadAsync()) { backgroundMat = Mat.FromStream(backgroundStream, ImreadModes.Unchanged); // Unchanged: Preserve transparency information } // Resize background image to target size if (backgroundMat.Width > targetWidth || backgroundMat.Height > targetHeight) { Cv2.Resize(backgroundMat, backgroundMat, new OpenCvSharp.Size(targetWidth, targetHeight)); } return backgroundMat; } private async Task TakePhotoAndCompositeWithOpenCVAsync() { try { // Take photo var renderTargetBitmap = new RenderTargetBitmap(); await renderTargetBitmap.RenderAsync(CameraPreview); var pixelBuffer = await renderTargetBitmap.GetPixelsAsync(); var capturedBitmap = new WriteableBitmap(renderTargetBitmap.PixelWidth, renderTargetBitmap.PixelHeight); using (var stream = capturedBitmap.PixelBuffer.AsStream()) { await stream.WriteAsync(pixelBuffer.ToArray(), 0, (int)pixelBuffer.Length); } // Convert WriteableBitmap to OpenCV Mat Mat capturedMat = WriteableBitmapToMat(capturedBitmap); // Load and resize background image from Pictures folder var picturesFolder = await StorageFolder.GetFolderFromPathAsync(Environment.GetFolderPath(Environment.SpecialFolder.MyPictures)); var backgroundFile = await picturesFolder.GetFileAsync("background.png"); // Load and resize background image (e.g., resize to 1920x1080) Mat backgroundMat = await LoadAndResizeBackgroundImageAsync(backgroundFile, 1920, 1080); // Extract transparent areas as a mask (alpha channel value of 0) Mat[] bgChannels = new Mat[4]; Cv2.Split(backgroundMat, out bgChannels); Mat alphaChannel = bgChannels[3]; // Binarize transparent areas (white for alpha value 0, black for others) Mat transparentMask = new Mat(); Cv2.Threshold(alphaChannel, transparentMask, 0, 255, ThresholdTypes.BinaryInv); // Find transparent regions using connected component labeling Mat labels = new Mat(); Mat stats = new Mat(); Mat centroids = new Mat(); int numLabels = Cv2.ConnectedComponentsWithStats(transparentMask, labels, stats, centroids); // Find the largest transparent region int largestLabel = 0; int largestArea = 0; for (int i = 1; i < numLabels; i++) // Exclude label 0 (background) { int area = stats.At<int>(i, 4); // Area is the 4th index if (area > largestArea) { largestArea = area; largestLabel = i; } } // Get coordinates of the largest region int x = stats.At<int>(largestLabel, 0); // Left (0th index) int y = stats.At<int>(largestLabel, 1); // Top (1st index) int width = stats.At<int>(largestLabel, 2); // Width (2nd index) int height = stats.At<int>(largestLabel, 3); // Height (3rd index) // Resize captured image to fit transparent area while maintaining aspect ratio double aspectRatio = (double)capturedMat.Width / capturedMat.Height; int newWidth, newHeight; // Compare aspect ratios and resize accordingly if ((double)width / height > aspectRatio) { newWidth = width; newHeight = (int)(width / aspectRatio); // Fit to width } else { newHeight = height; newWidth = (int)(aspectRatio * height); // Fit to height } // Resize captured image to the calculated size Mat resizedCapturedMat = new Mat(); Cv2.Resize(capturedMat, resizedCapturedMat, new OpenCvSharp.Size(newWidth, newHeight)); // Calculate offsets for centering (crop overflowing parts) int offsetX = x - (newWidth - width) / 2; // Move left by half of the overflow int offsetY = y - (newHeight - height) / 2; // Move up by half of the overflow // Center in transparent area for (int i = 0; i < height; i++) { for (int j = 0; j < width; j++) { int srcY = i + (newHeight - height) / 2; int srcX = j + (newWidth - width) / 2; if (srcY >= 0 && srcY < resizedCapturedMat.Height && srcX >= 0 && srcX < resizedCapturedMat.Width) { Vec3b fgPixel = resizedCapturedMat.At<Vec3b>(srcY, srcX); // Pixel from captured image (BGR) backgroundMat.Set(y + i, x + j, new Vec4b(fgPixel[0], fgPixel[1], fgPixel[2], 255)); // Composite onto background image } } } // Convert Mat to WriteableBitmap WriteableBitmap resultBitmap = MatToWriteableBitmap(backgroundMat); // Display composited image CapturedImage.Source = resultBitmap; CapturedImage.Visibility = Visibility.Visible; CameraPreview.Visibility = Visibility.Collapsed; // Show buttons ButtonPanel.Opacity = 1; // Release resources capturedMat.Dispose(); resizedCapturedMat.Dispose(); backgroundMat.Dispose(); transparentMask.Dispose(); labels.Dispose(); stats.Dispose(); centroids.Dispose(); _isPreviewing = false; } catch (Exception ex) { System.Diagnostics.Debug.WriteLine($"An error occurred in TakePhotoAndCompositeWithOpenCVAsync: {ex.Message}"); } } private void RetakeButton_Click(object sender, RoutedEventArgs e) { ButtonPanel.Opacity = 0; CapturedImage.Visibility = Visibility.Collapsed; CameraPreview.Visibility = Visibility.Visible; _isPreviewing = true; } private void PrintButton_Click(object sender, RoutedEventArgs e) { // Printing functionality to be implemented } } }