<div dir="ltr">Looks good to me <div class="gmail_extra"> <div class="gmail_quote">On Wed, Mar 16, 2016 at 9:14 PM, Søren Sandmann Pedersen <<a href="mailto:soren.sandmann@gmail.com" target="_blank">soren.sandmann@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Generalize and simplify the code that reduces BILINEAR to NEAREST so that all the reduction happens for all affine transformations where t00..t12 are integers and (t00 + t01) and (t10 + t11) are both odd. This is a sufficient condition for the resulting transformed coordinates to be exactly at the center of a pixel so that BILINEAR becomes identical to NEAREST. V2: Address some comments by Bill Spitzak Signed-off-by: Søren Sandmann <<a href="mailto:soren.sandmann@gmail.com">soren.sandmann@gmail.com</a>> --- pixman/pixman-image.c | 66 +++++++++++++++++++++++++++++---------------------- 1 file changed, 38 insertions(+), 28 deletions(-) diff --git a/pixman/pixman-image.c b/pixman/pixman-image.c index 1ff1a49..681864e 100644 --- a/pixman/pixman-image.c +++ b/pixman/pixman-image.c @@ -335,37 +335,47 @@ compute_image_info (pixman_image_t *image) { flags |= FAST_PATH_NEAREST_FILTER; } - else if ( - /* affine and integer translation components in matrix ... */ - ((flags & FAST_PATH_AFFINE_TRANSFORM) && - !pixman_fixed_frac (image->common.transform->matrix[0][2] | - image->common.transform->matrix[1][2])) && - ( - /* ... combined with a simple rotation */ - (flags & (FAST_PATH_ROTATE_90_TRANSFORM | - FAST_PATH_ROTATE_180_TRANSFORM | - FAST_PATH_ROTATE_270_TRANSFORM)) || - /* ... or combined with a simple non-rotated translation */ - (image->common.transform->matrix[0][0] == pixman_fixed_1 && - image->common.transform->matrix[1][1] == pixman_fixed_1 && - image->common.transform->matrix[0][1] == 0 && - image->common.transform->matrix[1][0] == 0) - ) - ) + else if (flags & FAST_PATH_AFFINE_TRANSFORM) { - /* FIXME: there are some affine-test failures, showing that - * handling of BILINEAR and NEAREST filter is not quite - * equivalent when getting close to 32K for the translation - * components of the matrix. That's likely some bug, but for - * now just skip BILINEAR->NEAREST optimization in this case. + /* Suppose the transform is + * + * [ t00, t01, t02 ] + * [ t10, t11, t12 ] + * [ 0, 0, 1 ] + * + * and the destination coordinates are (n + 0.5, m + 0.5). Then + * the transformed x coordinate is: + * + * tx = t00 * (n + 0.5) + t01 * (m + 0.5) + t02 + * = t00 * n + t01 * m + t02 + (t00 + t01) * 0.5 + * + * which implies that if t00, t01 and t02 are all integers + * and (t00 + t01) is odd, then tx will be an integer plus 0.5, + * which means a BILINEAR filter will reduce to NEAREST. The same + * applies in the y direction */ - pixman_fixed_t magic_limit = pixman_int_to_fixed (30000); - if (image->common.transform->matrix[0][2] <= magic_limit && - image->common.transform->matrix[1][2] <= magic_limit && - image->common.transform->matrix[0][2] >= -magic_limit && - image->common.transform->matrix[1][2] >= -magic_limit) + pixman_fixed_t (*t)[3] = image->common.transform->matrix; + + if ((pixman_fixed_frac ( + t[0][0] | t[0][1] | t[0][2] | + t[1][0] | t[1][1] | t[1][2]) == 0) && + (pixman_fixed_to_int ( + (t[0][0] + t[0][1]) & (t[1][0] + t[1][1])) % 2) == 1) </blockquote><div> </div><div>Very clever! This optimization looks correct.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> { - flags |= FAST_PATH_NEAREST_FILTER; + /* FIXME: there are some affine-test failures, showing that + * handling of BILINEAR and NEAREST filter is not quite + * equivalent when getting close to 32K for the translation + * components of the matrix. That's likely some bug, but for + * now just skip BILINEAR->NEAREST optimization in this case. + */ + pixman_fixed_t magic_limit = pixman_int_to_fixed (30000); + if (image->common.transform->matrix[0][2] <= magic_limit && + image->common.transform->matrix[1][2] <= magic_limit && + image->common.transform->matrix[0][2] >= -magic_limit && + image->common.transform->matrix[1][2] >= -magic_limit) + { + flags |= FAST_PATH_NEAREST_FILTER; + } } } break; -- 1.7.11.7 _______________________________________________ Pixman mailing list <a href="mailto:Pixman@lists.freedesktop.org">Pixman@lists.freedesktop.org</a> <a href="https://lists.freedesktop.org/mailman/listinfo/pixman" rel="noreferrer" target="_blank">https://lists.freedesktop.org/mailman/listinfo/pixman</a> </blockquote></div> </div></div>