Address 3848

src/__init__.py

@@ -10021,11 +10021,14 @@ def color_count(self, colors=0, clip=None):
 
     def color_topusage(self, clip=None):
         """Return most frequent color and its usage ratio."""
+        if clip is not None:
+            clip = IRect(self.irect) & clip
+            if clip.is_empty:
+                raise ValueError("clip must not be empty")
         allpixels = 0
         cnt = 0
-        if clip is not None and self.irect in Rect(clip):
-            clip = self.irect
-        for pixel, count in self.color_count(colors=True,clip=clip).items():
+
+        for pixel, count in self.color_count(colors=True, clip=clip).items():
             allpixels += count
             if count > cnt:
                 cnt = count

src/utils.py

@@ -881,6 +881,9 @@ def get_pixmap(
     if colorspace.n not in (1, 3, 4):
         raise ValueError("unsupported colorspace")
 
+    if clip is not None and pymupdf.IRect(clip).is_empty:
+        raise ValueError("clip must not be empty")
+
     dl = page.get_displaylist(annots=annots)
     pix = dl.get_pixmap(matrix=matrix, colorspace=colorspace, alpha=alpha, clip=clip)
     dl = None

tests/test_pixmap.py

@@ -264,6 +264,16 @@ def test_3177():
     pixmap = pymupdf.Pixmap(path)
     pixmap2 = pymupdf.Pixmap(None, pixmap)
 
+def test_3848():
+    path = os.path.abspath(f"{__file__}/../../tests/resources/img-transparent.png")
+    pix = pymupdf.Pixmap(path)
+    error = False
+    try:
+        top = pix.color_topusage(clip=(0, 0, 0, 0))
+    except ValueError:
+        error = True
+    assert error
+
 
 def test_3493():
     '''