From d8f5f47084245b5b2d589d60db316f8943a96c5b Mon Sep 17 00:00:00 2001
From: Leo Howell <leo@lwh.jp>
Date: Sat, 5 Sep 2009 17:27:50 +0900
Subject: Correct formula for capacity

---
 lpg/libqr/code-common.c | 29 ++++++++++++++++++-----------
 lpg/libqr/code-common.h |  1 -
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/lpg/libqr/code-common.c b/lpg/libqr/code-common.c
index 08b16df..25c1115 100644
--- a/lpg/libqr/code-common.c
+++ b/lpg/libqr/code-common.c
@@ -19,18 +19,25 @@ int code_side_length(int format)
         return format * 4 + 17;
 }
 
-int code_finder_count(int format)
-{
-        int x = format / 7;
-        return format > 1 ? x*x + 4*x + 1 : 0;        
-}
-
 size_t code_total_capacity(int format)
 {
-        /* XXX: figure out the "correct" formula */
-        return 160
-             +  25 * code_finder_count(format)
-             -  10 * (format / 7)
-             +   2 * code_side_length(format);
+	int side = format * 4 + 17;
+
+	int alignment_side = format > 1 ? (format / 7) + 2 : 0;
+
+	int alignment_count = alignment_side >= 2 ?
+		alignment_side * alignment_side - 3 : 0;
+
+	int locator_bits = 8*8*3;
+
+	int format_bits = 8*4 - 1 + (format >= 7 ? 6*3*2 : 0);
+
+	int timing_bits = 2 * (side - 8*2 -
+		(alignment_side > 2 ? (alignment_side - 2) * 5 : 0));
+
+	int function_bits = timing_bits + format_bits + locator_bits
+		+ alignment_count * 5*5;
+
+	return side * side - function_bits;
 }
 
diff --git a/lpg/libqr/code-common.h b/lpg/libqr/code-common.h
index 52666e6..17a45d7 100644
--- a/lpg/libqr/code-common.h
+++ b/lpg/libqr/code-common.h
@@ -11,7 +11,6 @@ struct qr_code {
 };
 
 int code_side_length(int format);
-int code_finder_count(int format);
 
 size_t code_total_capacity(int format);
 
-- 
cgit v1.2.3-70-g09d2