The convolution of two BOX filters is simply the length of the interval where both are non-zero, so we can simply return width from the integral() function because the integration region has already been restricted to be such that both functions are non-zero on it.
This is both faster and more accurate than doing numerical integration. This patch is based on one by Bill Spitzak https://lists.freedesktop.org/archives/pixman/2016-March/004446.html with these changes: - Rebased to not assume any changes in the arguments to integral(). - Dropped the multiplication by scale - Added more details in the commit message. Signed-off-by: Søren Sandmann <soren.sandm...@gmail.com> --- pixman/pixman-filter.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/pixman/pixman-filter.c b/pixman/pixman-filter.c index c868723..32aaa9a 100644 --- a/pixman/pixman-filter.c +++ b/pixman/pixman-filter.c @@ -160,11 +160,15 @@ integral (pixman_kernel_t kernel1, double x1, pixman_kernel_t kernel2, double scale, double x2, double width) { + if (kernel1 == PIXMAN_KERNEL_BOX && kernel2 == PIXMAN_KERNEL_BOX) + { + return width; + } /* The LINEAR filter is not differentiable at 0, so if the * integration interval crosses zero, break it into two * separate integrals. */ - if (kernel1 == PIXMAN_KERNEL_LINEAR && x1 < 0 && x1 + width > 0) + else if (kernel1 == PIXMAN_KERNEL_LINEAR && x1 < 0 && x1 + width > 0) { return integral (kernel1, x1, kernel2, scale, x2, - x1) + -- 1.7.11.7 _______________________________________________ Pixman mailing list Pixman@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/pixman