Fix index bounds calculation for image slicing compatibility

Author: PierreRaybaut

CHANGELOG.md

@@ -63,6 +63,11 @@
 
 🛠️ Bug fixes:
 
+* Fixed index bounds calculation for image slicing compatibility:
+  * Corrected the calculation of maximum indices in `get_plot_coordinates` to ensure proper bounds when using NumPy array slicing
+  * Previously, the maximum indices were off by one, which could cause issues when extracting image data using the returned coordinates
+  * Now returns indices that correctly align with Python/NumPy slicing conventions (e.g., `[i1:i2+1, j1:j2+1]`)
+  * This fixes an historic bug that could lead to off-by-one errors when users extracted image data using the coordinates provided by this function
 * Fixed plot update after inserting a point using the `EditPointTool` on non-Windows platforms
 * [Issue #46](https://github.com/PlotPyStack/PlotPy/issues/46) - Contrast adjustment with 'Eliminate outliers' failed for float images with high dynamic range
 * [Issue #29](https://github.com/PlotPyStack/PlotPy/issues/29) - SelectTool: Selecting Another Shape Without Unselection

plotpy/items/image/base.py

@@ -230,23 +230,30 @@ def get_closest_index_rect(
              Defaults to True.
 
         Returns:
-            Closest image rectangular pixel area index bounds
+            Closest image rectangular pixel area index bounds compatible with
+            direct array slicing (e.g., data[iy0:iy1, ix0:ix1])
 
         .. note::
 
             Avoid returning empty rectangular area (return 1x1 pixel area instead).
             Handle reversed/not-reversed Y-axis orientation.
+            Indices are compatible with direct array slicing and match get_data
+            behavior.
         """
         ix0, iy0 = self.get_closest_indexes(x0, y0, corner="TL")
-        ix1, iy1 = self.get_closest_indexes(x1, y1, corner="BR")
+        # Use TL to avoid double +1 addition
+        ix1, iy1 = self.get_closest_indexes(x1, y1, corner="TL")
         if ix0 > ix1:
             ix1, ix0 = ix0, ix1
         if iy0 > iy1:
             iy1, iy0 = iy0, iy1
+        # Add +1 to bottom-right indices for slice compatibility (matches get_data)
+        ix1 = min(ix1 + 1, self.data.shape[1])
+        iy1 = min(iy1 + 1, self.data.shape[0])
         if ix0 == ix1 and avoid_empty:
-            ix1 += 1
+            ix1 = min(ix1 + 1, self.data.shape[1])
         if iy0 == iy1 and avoid_empty:
-            iy1 += 1
+            iy1 = min(iy1 + 1, self.data.shape[0])
         return ix0, iy0, ix1, iy1
 
     def align_rectangular_shape(self, shape: RectangleShape) -> None: