fixup

Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>

Author: neutrinoceros

lib/matplotlib/backends/backend_pdf.py

@@ -1784,8 +1784,7 @@ def _writeImg(self, data, id, smask=None):
                          data[:, :, 2])
                 indices = np.argsort(palette24).astype(np.uint8)
                 rgb8 = indices[np.searchsorted(palette24, rgb24, sorter=indices)]
-                img = Image.fromarray(rgb8)
-                img.convert("P")
+                img = Image.fromarray(rgb8).convert("P")
                 img.putpalette(palette)
                 png_data, bit_depth, palette = self._writePng(img)
                 if bit_depth is None or palette is None: