Commit ae21e087 authored by Alexander Larsson's avatar Alexander Larsson

gtkcairoblur: Minor restructure

This just moves get_box_filter_size to the top and makes
it a macro (so it can be used as a constant later).

https://bugzilla.gnome.org/show_bug.cgi?id=746468
parent 9ba185b7
......@@ -25,6 +25,19 @@
#include <math.h>
#include <string.h>
/*
* Gets the size for a single box blur.
*
* Much of this, the 3 * sqrt(2 * pi) / 4, is the known value for
* approximating a Gaussian using box blurs. This yields quite a good
* approximation for a Gaussian. For more details, see:
* http://www.w3.org/TR/SVG11/filters.html#feGaussianBlurElement
* https://bugzilla.mozilla.org/show_bug.cgi?id=590039#c19
*/
#define GAUSSIAN_SCALE_FACTOR ((3.0 * sqrt(2 * G_PI) / 4))
#define get_box_filter_size(radius) ((int)(GAUSSIAN_SCALE_FACTOR * radius))
/* This applies a single box blur pass to a horizontal range of pixels;
* since the box blur has the same weight for all pixels, we can
* implement an efficient sliding window algorithm where we add
......@@ -140,23 +153,6 @@ flip_buffer (guchar *dst_buffer,
#undef BLOCK_SIZE
}
/*
* Gets the size for a single box blur.
*
* Much of this, the 3 * sqrt(2 * pi) / 4, is the known value for
* approximating a Gaussian using box blurs. This yields quite a good
* approximation for a Gaussian. For more details, see:
* http://www.w3.org/TR/SVG11/filters.html#feGaussianBlurElement
* https://bugzilla.mozilla.org/show_bug.cgi?id=590039#c19
*/
#define GAUSSIAN_SCALE_FACTOR ((3.0 * sqrt(2 * G_PI) / 4))
static int
get_box_filter_size (double radius)
{
return GAUSSIAN_SCALE_FACTOR * radius;
}
static void
_boxblur (guchar *buffer,
int width,
......
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