ImageCroppingViewModel.cs

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using NeuroAccessMaui.UI.Controls;
using System.Threading.Tasks;
using Waher.Content.QR.Serialization;
 
namespace NeuroAccessMaui.UI.Pages.Utility.Images
{
    public partial class ImageCroppingViewModel : BaseViewModel
    {
        private readonly ImageCroppingNavigationArgs? args;
 
        [ObservableProperty]
        private ImageCropperView? imageCropperView;
 
        public ImageCroppingViewModel(ImageCroppingNavigationArgs? args)
        {
            this.args = args;
        }
 
        public override async Task OnAppearingAsync()
        {
            await base.OnAppearingAsync();
 
            if (this.args?.Source is not null && this.ImageCropperView is not null)
            {
                // Assign the incoming source to the cropper control.
                this.ImageCropperView.ImageSource = this.args.Source;
            }
 
            if (this.args?.OutputResolution is not null && this.ImageCropperView is not null)
            {
                this.ImageCropperView.OutputMaxResolution = this.args.OutputResolution.Value;
            }
 
            if (this.args?.CropMode is not null && this.ImageCropperView is not null)
            {
                this.ImageCropperView.CropMode = this.args.CropMode;
            }
        }
 
        [RelayCommand]
        private async Task CropAsync()
        {
            if (this.ImageCropperView is null || this.args is null)
                return;
                
            //Run the crop operation on a background thread.
            await Task.Run(() => 
            {
                byte[]? CroppedResult = this.ImageCropperView.PerformCrop();
                this.args.CompletionSource?.TrySetResult(CroppedResult);
            });
            // Then pop navigation.
            await this.GoBack();
        }
 
        [RelayCommand]
        private async Task CancelAsync()
        {
            this.args?.CompletionSource?.SetResult(null);
            await this.GoBack();
        }
 
        [RelayCommand]
        private Task RotateAsync()
        {
            if (this.ImageCropperView is not null)
            {
                // Increment the rotation angle by 90 degrees.
                double NewRotation = this.ImageCropperView.RotationAngle + 90;
                // Normalize the rotation angle to stay within 0-359 degrees.
                this.ImageCropperView.RotationAngle = NewRotation % 360;
            }
            return Task.CompletedTask;
        }
    }
}