allow resizing the crop box by dragging handles

Program.cs

@@ -122,10 +122,12 @@ public class ViewTool : ITool {
 
 public class CropTool : ITool {
 
+  enum Mode { Sizing, Translating };
+
   Photo photo;
   Vector2i mouseDragStart;
   Vector2i mouseDragEnd;
-  bool dragging;
+  Mode mode;
   string status = "";
 
   public CropTool(Photo photo) {
@@ -138,15 +140,38 @@ public class CropTool : ITool {
     Vector2i mousePosition = (Vector2i) mouse.Position;
     Vector2i imagePosition = transform.ScreenToImage(mousePosition);
 
+    List<Vector2i> corners = Util.RectangleCorners(photo.CropRectangle);
+    Vector2i? oppositeCorner = null;
+    bool mouseNearHandle = false;
+    for (int i = 0; i < 4; i++) {
+      Vector2i corner = corners[i];
+      Vector2i handlePosition = transform.ImageToScreen(corner.X, corner.Y);
+      if (Vector2i.Subtract(mousePosition, handlePosition).ManhattanLength < 10) {
+        mouseNearHandle = true;
+        oppositeCorner = corners[(i + 2) % 4];
+        break;
+      }
+    }
+
     bool mouseInRectangle = photo.CropRectangle.Contains(imagePosition.X, imagePosition.Y);
     if (mouse.IsButtonPressed(MouseButton.Button1)) {
-      dragging = mouseInRectangle;
+      if (mouseNearHandle || !mouseInRectangle) {
+        mode = Mode.Sizing;
+      } else {
+        mode = Mode.Translating;
+      }
+    }
+    if (mouseNearHandle) {
+      game.Cursor = MouseCursor.Hand;
+    } else if (mouseInRectangle) {
+      game.Cursor = MouseCursor.Default;
+    } else {
+      game.Cursor = MouseCursor.Crosshair;
     }
-    game.Cursor = mouseInRectangle ? MouseCursor.Default : MouseCursor.Crosshair;
 
-    if (!dragging) {
+    if (mode == Mode.Sizing) {
       if (mouse.IsButtonPressed(MouseButton.Button1)) {
-        mouseDragStart = imagePosition;
+        mouseDragStart = oppositeCorner ?? imagePosition;
       }
       if (mouse.IsButtonDown(MouseButton.Button1)) {
         mouseDragEnd = imagePosition;
@@ -297,6 +322,16 @@ public static class Util {
     return new Box2i(left, top, left + width, top + height);
   }
 
+  // resulting items are ordered such that a corner's opposite is 2 indexes away.
+  public static List<Vector2i> RectangleCorners(Rectangle r) {
+    List<Vector2i> result = new(4);
+    result.Add(new(r.Left, r.Top));
+    result.Add(new(r.Right, r.Top));
+    result.Add(new(r.Right, r.Bottom));
+    result.Add(new(r.Left, r.Bottom));
+    return result;
+  }
+
   public static Image<Rgba32> MakeImage(float width, float height) {
     return new((int) Math.Ceiling(width), (int) Math.Ceiling(height));
   }
@@ -724,8 +759,8 @@ public class Game : GameWindow {
     // string[] files = Directory.GetFiles(@"c:\users\colin\pictures\photos\2023\07\14\");
     // string[] files = Directory.GetFiles(@"c:\users\colin\pictures\photos\2023\09\06\jpg");
     // string[] files = Directory.GetFiles(@"G:\DCIM\100EOSR6\");
-    // string[] files = Directory.GetFiles(@"c:\users\colin\desktop\totte-output\2023\08\29");
-    string[] files = Directory.GetFiles(@"c:\users\colin\desktop\export");
+    string[] files = Directory.GetFiles(@"c:\users\colin\desktop\totte-output\2023\08\03");
+    // string[] files = Directory.GetFiles(@"c:\users\colin\desktop\export");
     // string[] files = Directory.GetFiles(@"C:\Users\colin\Pictures\photos\2018\06\23");
     // string[] files = Directory.GetFiles(@"C:\Users\colin\Desktop\Germany all\104D7000");
     // string[] files = Directory.GetFiles(@"C:\Users\colin\Desktop\many-birds\");