Added PowerPoint templates to the Slide Assistant (#1055)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/MindWork AI Studio/Tools/PowerPoint/RustPictureSource.cs

@@ -0,0 +1,38 @@
+using AIStudio.Tools.Services;
+
+namespace AIStudio.Tools.PowerPoint;
+
+/// <summary>
+/// Loads the attached pictures through the runtime.
+/// </summary>
+/// <remarks>
+/// The runtime checks that each file is the image its extension claims, and scales large pictures
+/// down, so that a presentation full of photos stays small enough to send by mail.
+/// </remarks>
+/// <param name="rustService">The runtime.</param>
+/// <param name="picturePaths">The paths of the pictures the slides use, by the numbers the model gave them.</param>
+/// <param name="iconNumbers">The numbers of the pictures which are icons of a picture library.</param>
+internal sealed class RustPictureSource(RustService rustService, IReadOnlyDictionary<int, string> picturePaths, IReadOnlySet<int> iconNumbers) : IPictureSource
+{
+    /// <inheritdoc />
+    public async Task<SlidePicture?> LoadAsync(int number, CancellationToken token)
+    {
+        if (!picturePaths.TryGetValue(number, out var picturePath))
+            return null;
+
+        try
+        {
+            var prepared = await rustService.PrepareImageAsync(picturePath, true, token);
+            var dataStart = prepared.DataUrl.IndexOf(',');
+            if (dataStart < 0)
+                return null;
+
+            return new SlidePicture(Convert.FromBase64String(prepared.DataUrl[(dataStart + 1)..]), prepared.MimeType, (int)prepared.Width, (int)prepared.Height, iconNumbers.Contains(number));
+        }
+        catch (Exception e) when (e is not OperationCanceledException)
+        {
+            // The slot stays empty, and the writer reports the picture as skipped:
+            return null;
+        }
+    }
+}