From dbffea4ff7adeae96a635c4fc1e13504a6cf2ad6 Mon Sep 17 00:00:00 2001
From: Tor Andersson <tor.andersson@artifex.com>
Date: Tue, 16 Oct 2018 22:01:06 +0200
Subject: Handle premultiplied alpha in pixmap color conversions (CMYK only).

---
 include/mupdf/fitz/geometry.h | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'include')

diff --git a/include/mupdf/fitz/geometry.h b/include/mupdf/fitz/geometry.h
index f04e8f1c..2314bea1 100644
--- a/include/mupdf/fitz/geometry.h
+++ b/include/mupdf/fitz/geometry.h
@@ -14,6 +14,14 @@ static inline int fz_mul255(int a, int b)
 	return x >> 8;
 }
 
+/*
+	Undo alpha premultiplication.
+*/
+static inline int fz_div255(int c, int a)
+{
+	return a ? c * (255 * 256 / a) >> 8 : 0;
+}
+
 /*
 	Expand a value A from the 0...255 range to the 0..256 range
 */
-- 
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