<div dir="ltr">Okay, thanks for the info. Will try to fix them all.</div><div class="gmail_extra"> <div class="gmail_quote">On Mon, Feb 1, 2016 at 5:51 AM, Oded Gabbay <<a href="mailto:oded.gabbay@gmail.com" target="_blank">oded.gabbay@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="HOEnZb"><div class="h5">On Fri, Jan 22, 2016 at 11:41 AM, <<a href="mailto:spitzak@gmail.com">spitzak@gmail.com</a>> wrote: > > From: Bill Spitzak <<a href="mailto:spitzak@gmail.com">spitzak@gmail.com</a>> > > This is much more accurate and less blurry. In particular the filtering does > not change as the image is rotated. > > Signed-off-by: Bill Spitzak <<a href="mailto:spitzak@gmail.com">spitzak@gmail.com</a>> > --- > demos/scale.c | 102 +++++++++++++++++++++++++++++++++++----------------------- > 1 file changed, 61 insertions(+), 41 deletions(-) > > diff --git a/demos/scale.c b/demos/scale.c > index d00307e..0995ad0 100644 > --- a/demos/scale.c > +++ b/demos/scale.c > @@ -55,50 +55,70 @@ get_widget (app_t *app, const char *name) > return widget; > } > > -static double > -min4 (double a, double b, double c, double d) > -{ > - double m1, m2; > - > - m1 = MIN (a, b); > - m2 = MIN (c, d); > - return MIN (m1, m2); > -} > - > -static double > -max4 (double a, double b, double c, double d) > -{ > - double m1, m2; > - > - m1 = MAX (a, b); > - m2 = MAX (c, d); > - return MAX (m1, m2); > -} > - > +/* Figure out the boundary of a diameter=1 circle transformed into an ellipse > + * by trans. Proof that this is the correct calculation: > + * > + * Transform x,y to u,v by this matrix calculation: > + * > + * |u| |a c| |x| > + * |v| = |b d|*|y| > + * > + * Horizontal component: > + * > + * u = ax+cy (1) > + * > + * For each x,y on a radius-1 circle (p is angle to the point): > + * > + * x^2+y^2 = 1 > + * x = cos(p) > + * y = sin(p) > + * dx/dp = -sin(p) = -y > + * dy/dp = cos(p) = x > + * > + * Figure out derivative of (1) relative to p: > + * > + * du/dp = a(dx/dp) + c(dy/dp) > + * = -ay + cx > + * > + * The min and max u are when du/dp is zero: > + * > + * -ay + cx = 0 > + * cx = ay > + * c = ay/x (2) > + * y = cx/a (3) > + * > + * Substitute (2) into (1) and simplify: > + * > + * u = ax + ay^2/x > + * = a(x^2+y^2)/x > + * = a/x (because x^2+y^2 = 1) > + * x = a/u (4) > + * > + * Substitute (4) into (3) and simplify: > + * > + * y = c(a/u)/a > + * y = c/u (5) > + * > + * Square (4) and (5) and add: > + * > + * x^2+y^2 = (a^2+c^2)/u^2 > + * > + * But x^2+y^2 is 1: > + * > + * 1 = (a^2+c^2)/u^2 > + * u^2 = a^2+c^2 > + * u = hypot(a,c) > + * > + * Similarily the max/min of v is at: > + * > + * v = hypot(b,d) > + * > + */ > static void > compute_extents (pixman_f_transform_t *trans, double *sx, double *sy) > { > - double min_x, max_x, min_y, max_y; > - pixman_f_vector_t v[4] = > - { > - { { 1, 1, 1 } }, > - { { -1, 1, 1 } }, > - { { -1, -1, 1 } }, > - { { 1, -1, 1 } }, > - }; > - > - pixman_f_transform_point (trans, &v[0]); > - pixman_f_transform_point (trans, &v[1]); > - pixman_f_transform_point (trans, &v[2]); > - pixman_f_transform_point (trans, &v[3]); > - > - min_x = min4 (v[0].v[0], v[1].v[0], v[2].v[0], v[3].v[0]); > - max_x = max4 (v[0].v[0], v[1].v[0], v[2].v[0], v[3].v[0]); > - min_y = min4 (v[0].v[1], v[1].v[1], v[2].v[1], v[3].v[1]); > - max_y = max4 (v[0].v[1], v[1].v[1], v[2].v[1], v[3].v[1]); > - > - *sx = (max_x - min_x) / 2.0; > - *sy = (max_y - min_y) / 2.0; > + *sx = hypot (trans->m[0][0], trans->m[0][1]) / trans->m[2][2]; > + *sy = hypot (trans->m[1][0], trans->m[1][1]) / trans->m[2][2]; > } > > typedef struct > -- > 1.9.1 > </div></div>> _______________________________________________ > Pixman mailing list > <a href="mailto:Pixman@lists.freedesktop.org">Pixman@lists.freedesktop.org</a> > <a href="http://lists.freedesktop.org/mailman/listinfo/pixman" rel="noreferrer" target="_blank">http://lists.freedesktop.org/mailman/listinfo/pixman</a> Reviewed-by: Oded Gabbay <<a href="mailto:oded.gabbay@gmail.com">oded.gabbay@gmail.com</a>> p.s. if we have additional versions of this patch series, and patches that got r-b are not modified, then please add my r-b to the patch so I would know I don't need to spend even a second over that patch. Thanks </blockquote></div> </div>