From fc5a9023e51a01c2c89296b5e2897faf5d183f4d Mon Sep 17 00:00:00 2001
From: Lukas Geiger <lukas.geiger94@gmail.com>
Date: Tue, 23 Sep 2025 12:36:35 +0100
Subject: [PATCH] Increase buffer size to speedup `Image.tobytes()`

---
 src/PIL/Image.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index b17fd131d..b1c3829d0 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -793,7 +793,11 @@ class Image:
 
         from . import ImageFile
 
-        bufsize = max(ImageFile.MAXBLOCK, self.size[0] * 4)  # see RawEncode.c
+        mode_descr = ImageMode.getmode(self.mode)
+        bytes_per_value = int(mode_descr.typestr[-1])
+        channels = len(mode_descr.bands)
+        bufsize = self.height * self.width * channels * bytes_per_value
+        bufsize = max(ImageFile.MAXBLOCK, bufsize)  # see RawEncode.c
 
         output = []
         while True: