gh-151888: Add tkinter PhotoImage.redither method

Doc/library/tkinter.rst

@@ -6076,6 +6076,14 @@ Image classes
       it is displayed as transparent and the background of whatever window it
       is displayed in shows through.
 
+   .. method:: redither()
+
+      Recalculate the dithered image in each window where it is displayed.
+      This is useful when the image data was supplied in pieces, in which case
+      the dithered image may not be exactly correct.
+
+      .. versionadded:: next
+
    .. method:: cget(option)
 
       Return the current value of the configuration option *option*.

Doc/whatsnew/3.16.rst

@@ -194,6 +194,11 @@ tkinter
   badge) and :meth:`~tkinter.Wm.wm_stackorder` (toplevel stacking order).
   (Contributed by Serhiy Storchaka in :gh:`151874`.)
 
+* Added the :meth:`~tkinter.PhotoImage.redither` method which recalculates the
+  dithered image when its data was supplied in pieces.
+  (Contributed by Serhiy Storchaka in :gh:`151888`.)
+
+
 xml
 ---
 

Lib/test/test_tkinter/test_images.py

@@ -311,6 +311,12 @@ def test_blank(self):
         self.assertEqual(image.height(), 16)
         self.assertEqual(image.get(4, 6), self.colorlist(0, 0, 0))
 
+    def test_redither(self):
+        image = self.create()
+        pixel = image.get(4, 6)
+        image.redither()  # Recalculates the dithering; the data is unchanged.
+        self.assertEqual(image.get(4, 6), pixel)
+
     def test_copy(self):
         image = self.create()
         image2 = image.copy()

Lib/tkinter/__init__.py

@@ -4571,6 +4571,13 @@ def blank(self):
         """Display a transparent image."""
         self.tk.call(self.name, 'blank')
 
+    def redither(self):
+        """Recalculate the dithered image in each window where it is displayed.
+
+        Useful when the image data was supplied in pieces, in which case the
+        dithered image may not be exactly correct."""
+        self.tk.call(self.name, 'redither')
+
     def cget(self, option):
         """Return the value of OPTION."""
         return self.tk.call(self.name, 'cget', '-' + option)

Misc/NEWS.d/next/Library/2026-06-22-01-57-55.gh-issue-151888.hO7mxi.rst

@@ -0,0 +1,2 @@
+Add the :meth:`!tkinter.PhotoImage.redither` method, wrapping the photo image
+``redither`` Tk command.