From: Bill Spitzak <[email protected]> v8: first version
Signed-off-by: Bill Spitzak <[email protected]> --- pixman/pixman-filter.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/pixman/pixman-filter.c b/pixman/pixman-filter.c index 3237036..0961cfc 100644 --- a/pixman/pixman-filter.c +++ b/pixman/pixman-filter.c @@ -313,7 +313,28 @@ gnuplot_filter(int width, int samples, const pixman_fixed_t* p) #endif /* Create the parameter list for a SEPARABLE_CONVOLUTION filter - * with the given kernels and scale parameters + * + * The reconstruct filter is scaled by 1, while the sample filter is + * scaled by scale, and they are convolved together. Note that scale + * is the inverse of how the image is being scaled, if the image is + * being made smaller, the filter gets larger. + * + * Some interesting reconstruct.sample combinations: + * + * IMPULSE.x - Uses the sample function only. Only works for scale >= 1. This + * is useful for matching other software that does not convolve, + * for large scale it is almost identical to BOX.x but the filter + * is slightly smaller and thus faster. + * x.IMPULSE - Uses the reconstruct function only, scale is ignored. + * LINEAR.IMPULSE - Matches bilinear filtering + * BOX.BOX - Produces a trapazoid-shape. Narrowest possible filter with antialiasing. + * This is equal to LINEAR.IMPULSE at scale == 1. Matches a lot of other + * software, some call it "box", others call it "linear" + * IMPULSE.LINEAR - Some software calls this "linear" or "triangle". Not a good filter. + * LINEAR.LINEAR - non-negative cubic. What some software calls "cubic interpolation". + * IMPULSE.LANCZOS2 - Close to what a lot of other software calls "cubic interpolation" + * IMPULSE.CUBIC - Often called "mitchell" in other software + * IMPULSE.GAUSSIAN - Technically accurate but usually considered too blurry */ PIXMAN_EXPORT pixman_fixed_t * pixman_filter_create_separable_convolution (int *n_values, -- 1.9.1 _______________________________________________ Pixman mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/pixman
