From 8ef38e99109c62f52d9c00c69dfae2531b16e472 Mon Sep 17 00:00:00 2001
From: Christophe CURIS <christophe.curis@free.fr>
Date: Sat, 11 May 2013 00:07:16 +0200
Subject: [PATCH] WRaster: Changed equality/inequality comparison on floating
 point number

The equality comparison (a == b) is known to be a dangerous trap
when floating-point arithmetics are involved. This patch changes
all the cases which try to do this to a safer check.
---
 wrlib/png.c    |  2 +-
 wrlib/rotate.c | 21 +++++++++++++++++----
 wrlib/scale.c  | 14 +++++++++++++-
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/wrlib/png.c b/wrlib/png.c
index fed178e1..03074ead 100644
--- a/wrlib/png.c
+++ b/wrlib/png.c
@@ -140,7 +140,7 @@ RImage *RLoadPNG(RContext *context, const char *file)
 		sgamma = (context->attribs->rgamma + context->attribs->ggamma + context->attribs->bgamma) / 3;
 	} else if ((tmp = getenv("DISPLAY_GAMMA")) != NULL) {
 		sgamma = atof(tmp);
-		if (sgamma == 0)
+		if (sgamma < 1.0E-3)
 			sgamma = 1;
 	} else {
 		/* blah */
diff --git a/wrlib/rotate.c b/wrlib/rotate.c
index b1379ba3..d296815a 100644
--- a/wrlib/rotate.c
+++ b/wrlib/rotate.c
@@ -43,12 +43,23 @@ RImage *RRotateImage(RImage * image, float angle)
 	int x, y;
 	int bpp = image->format == RRGBAFormat ? 4 : 3;
 
+	/*
+	 * Angle steps below this value would represent a rotation
+	 * of less than 1 pixel for a 4k wide image, so not worth
+	 * bothering the difference. That makes it a perfect
+	 * candidate for an Epsilon when trying to compare angle
+	 * to known values
+	 */
+	static const float min_usable_angle = 0.00699;
+
 	angle = ((int)angle % 360) + (angle - (int)angle);
 
-	if (angle == 0.0) {
+	if (angle < min_usable_angle) {
+		/* Rotate by 0 degree */
 		return RCloneImage(image);
 
-	} else if (angle == 90.0) {
+	} else if ((angle > 90.0 - min_usable_angle) &&
+				  (angle < 90.0 + min_usable_angle)) {
 		nwidth = image->height;
 		nheight = image->width;
 
@@ -91,7 +102,8 @@ RImage *RRotateImage(RImage * image, float angle)
 				}
 			}
 		}
-	} else if (angle == 180.0) {
+	} else if ((angle > 180.0 - min_usable_angle) &&
+				  (angle < 180.0 + min_usable_angle)) {
 
 		nwidth = image->width;
 		nheight = image->height;
@@ -129,7 +141,8 @@ RImage *RRotateImage(RImage * image, float angle)
 				nptr--;
 			}
 		}
-	} else if (angle == 270.0) {
+	} else if ((angle > 270.0 - min_usable_angle) &&
+				  (angle < 270.0 + min_usable_angle)) {
 		nwidth = image->height;
 		nheight = image->width;
 
diff --git a/wrlib/scale.c b/wrlib/scale.c
index 6990afe2..d2cc1e6c 100644
--- a/wrlib/scale.c
+++ b/wrlib/scale.c
@@ -187,8 +187,20 @@ static double B_spline_filter(double t)   /* box (*) box (*) box (*) box */
 
 static double sinc(double x)
 {
+	/*
+	 * The original code did this:
+	 *   if (x != 0) ...
+	 * This code is unsafe, it should be:
+	 *   if (fabs(x) > EPSILON) ...
+	 *
+	 * But the call to fabs is already done in the *ONLY* function
+	 * that call sinc: 'Lanczos3_filter'
+	 *
+	 * The goal was to avoid a Divide-by-0 error, now we also
+	 * avoid a +/-inf result too
+	 */
 	x *= PI;
-	if (x != 0)
+	if (x > 1.0E-9)
 		return (sin(x) / x);
 	return (1.0);
 }
-- 
2.11.4.GIT