fdo-mirrors/cairo
1
0
Fork 0
mirror of https://gitlab.freedesktop.org/cairo/cairo.git synced 2026-01-05 09:10:19 +01:00
Code Issues Projects Releases Packages Wiki Activity Actions

Corrected some confusing comments about the math used for radial gradients

Browse source
This commit is contained in:
David Reveman 2004-05-04 04:01:18 +00:00
parent 1876568f20
commit 423ea55410
3 changed files with 37 additions and 16 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
ChangeLog
View file

@ -1,3 +1,8 @@
2004-05-04 David Reveman <c99drn@cs.umu.se>
* src/cairo_pattern.c (_cairo_image_data_set_radial): Corrected some
confusing comments about the math used for radial gradients.
2004-05-01 David Reveman <c99drn@cs.umu.se>
* src/cairo_gl_surface.c (_cairo_gl_surface_create_pattern):

24
src/cairo-pattern.c
View file

@ -620,20 +620,28 @@ _cairo_image_data_set_radial (cairo_pattern_t *pattern,
factor = (sqrt (ex * ex + ey * ey) - r0) * r1;
} else {
/* Here we need to calulate distance c0 -> x; the distance from
the inner circle center c0, through point (ex, ey) to
point x where it crosses the outer circle. The gradient offset
can then be calculated within the distance of the inner and
outer circles.
y y_x (ex, ey)
/*
y (ex, ey)
c0 -------------------+---------- x
\ | __--
\ | __--
r0 \ | c1_y __--
\ | __--
\ | __-- r1
\ | __--
c1 --
We need to calulate distance c0->x; the distance from
the inner circle center c0, through fragment position
(ex, ey) to point x where it crosses the outer circle.
From points c0, c1 and (ex, ey) we get angle C0. With
angle C0 we calculate distance c1->y and c0->y and by
knowing c1->y and r1, we also know y->x. Adding y->x to
c0->y gives us c0->x. The gradient offset can then be
calculated as:
offset = (c0->e - r0) / (c0->x - r0)
*/
c0_e_x = ex - c0.x;

24
src/cairo_pattern.c
View file

@ -620,20 +620,28 @@ _cairo_image_data_set_radial (cairo_pattern_t *pattern,
factor = (sqrt (ex * ex + ey * ey) - r0) * r1;
} else {
/* Here we need to calulate distance c0 -> x; the distance from
the inner circle center c0, through point (ex, ey) to
point x where it crosses the outer circle. The gradient offset
can then be calculated within the distance of the inner and
outer circles.
y y_x (ex, ey)
/*
y (ex, ey)
c0 -------------------+---------- x
\ | __--
\ | __--
r0 \ | c1_y __--
\ | __--
\ | __-- r1
\ | __--
c1 --
We need to calulate distance c0->x; the distance from
the inner circle center c0, through fragment position
(ex, ey) to point x where it crosses the outer circle.
From points c0, c1 and (ex, ey) we get angle C0. With
angle C0 we calculate distance c1->y and c0->y and by
knowing c1->y and r1, we also know y->x. Adding y->x to
c0->y gives us c0->x. The gradient offset can then be
calculated as:
offset = (c0->e - r0) / (c0->x - r0)
*/
c0_e_x = ex - c0.x;