From d707a4778f49637d9a061edc422b1d50f4397257 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Wed, 8 Jul 2015 10:55:46 +0530
Subject: [PATCH] Conversion: Fix error when input document contains a font
 size exactly one point away from the base size. Fixes #1472291 [Convert from
 HTM to mobi](https://bugs.launchpad.net/calibre/+bug/1472291)

---
 src/calibre/ebooks/oeb/transforms/flatcss.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/calibre/ebooks/oeb/transforms/flatcss.py b/src/calibre/ebooks/oeb/transforms/flatcss.py
index b736458a87..3c42877c1b 100644
--- a/src/calibre/ebooks/oeb/transforms/flatcss.py
+++ b/src/calibre/ebooks/oeb/transforms/flatcss.py
@@ -62,6 +62,8 @@ class KeyMapper(object):
         endp = 0 if size < base else 36
         diff = (abs(base - size) * 3) + ((36 - size) / 100)
         logb = abs(base - endp)
+        if logb == 1.0:
+            logb = 1.1
         try:
             result = sign * math.log(diff, logb)
         except ValueError: