From: Owen W. Taylor <otaylor@fishsoup.net>
Date: Mon, 18 Oct 2010 21:30:52 +0000 (-0400)
Subject: St: Fix blur radius computation to correspond to current CSS draft
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St: Fix blur radius computation to correspond to current CSS draft

The next draft of the CSS Backgrounds and Borders module will actually
define when the blur radius means. Fix our code to use that definition
(2 * standard deviation) rather than using the 1.9 * that we extracted
from what Mozilla was doing.

https://bugzilla.gnome.org/show_bug.cgi?id=632506
---

diff --git a/src/st/st-private.c b/src/st/st-private.c
index f97c2de7f..d0aa89bae 100644
--- a/src/st/st-private.c
+++ b/src/st/st-private.c
@@ -435,11 +435,12 @@ blur_pixels (guchar  *pixels_in,
   guchar *pixels_out;
   float   sigma;
 
-  /* we use an approximation of the sigma - blur radius relationship used
-     in Firefox for doing SVG blurs; see
-     http://mxr.mozilla.org/mozilla-central/source/gfx/thebes/src/gfxBlur.cpp#280
-  */
-  sigma = blur / 1.9;
+  /* The CSS specification defines (or will define) the blur radius as twice
+   * the Gaussian standard deviation. See:
+   *
+   * http://lists.w3.org/Archives/Public/www-style/2010Sep/0002.html
+   */
+  sigma = blur / 2.;
 
   if ((guint) blur == 0)
     {