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pattern: Use pattern parameter range when analysing all gradients.

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This patch adds support for analysing the transparency of a
radial gradient within some area of interest.  Before the code
would ignore the extents for radial gradients.  Linear gradients
now use _cairo_linear_pattern_box_to_parameter() allowing us
to remove the superfluous _extents_to_linear_parameter().

Reviewed-by: M Joonas Pihlaja <jpihlaja@cc.helsinki.fi>
This commit is contained in:
Andrea Canciani 2010-11-23 19:31:40 +01:00
parent 790837ac68
commit 08cb6db520
1 changed files with 46 additions and 53 deletions
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99
src/cairo-pattern.c
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@ -1728,38 +1728,6 @@ _cairo_pattern_reset_solid_surface_cache (void)
CAIRO_MUTEX_UNLOCK (_cairo_pattern_solid_surface_cache_lock);
}
static void
_extents_to_linear_parameter (const cairo_linear_pattern_t *linear,
const cairo_rectangle_int_t *extents,
double t[2])
{
double t0, tdx, tdy;
double p1x, p1y, pdx, pdy, invsqnorm;
p1x = _cairo_fixed_to_double (linear->p1.x);
p1y = _cairo_fixed_to_double (linear->p1.y);
pdx = _cairo_fixed_to_double (linear->p2.x) - p1x;
pdy = _cairo_fixed_to_double (linear->p2.y) - p1y;
invsqnorm = 1.0 / (pdx * pdx + pdy * pdy);
pdx *= invsqnorm;
pdy *= invsqnorm;
t0 = (extents->x - p1x) * pdx + (extents->y - p1y) * pdy;
tdx = extents->width * pdx;
tdy = extents->height * pdy;
t[0] = t[1] = t0;
if (tdx < 0)
t[0] += tdx;
else
t[1] += tdx;
if (tdy < 0)
t[0] += tdy;
else
t[1] += tdy;
}
static cairo_bool_t
_linear_pattern_is_degenerate (const cairo_linear_pattern_t *linear)
{
@ -2249,27 +2217,40 @@ _gradient_is_clear (const cairo_gradient_pattern_t *gradient,
gradient->stops[0].offset == gradient->stops[gradient->n_stops - 1].offset))
return TRUE;
/* Check if the extents intersect the drawn part of the pattern. */
if (gradient->base.type == CAIRO_PATTERN_TYPE_LINEAR) {
if (gradient->base.extend == CAIRO_EXTEND_NONE) {
cairo_linear_pattern_t *linear = (cairo_linear_pattern_t *) gradient;
/* EXTEND_NONE degenerate linear gradients are clear */
if (_linear_pattern_is_degenerate (linear))
return TRUE;
if (extents != NULL) {
double t[2];
_extents_to_linear_parameter (linear, extents, t);
if ((t[0] <= 0.0 && t[1] <= 0.0) || (t[0] >= 1.0 && t[1] >= 1.0))
return TRUE;
}
}
} else {
cairo_radial_pattern_t *radial = (cairo_radial_pattern_t *) gradient;
if (gradient->base.type == CAIRO_PATTERN_TYPE_RADIAL) {
/* degenerate radial gradients are clear */
if (_radial_pattern_is_degenerate (radial))
if (_radial_pattern_is_degenerate ((cairo_radial_pattern_t *) gradient))
return TRUE;
} else if (gradient->base.extend == CAIRO_EXTEND_NONE) {
/* EXTEND_NONE degenerate linear gradients are clear */
if (_linear_pattern_is_degenerate ((cairo_linear_pattern_t *) gradient))
return TRUE;
}
/* Check if the extents intersect the drawn part of the pattern. */
if (extents != NULL &&
(gradient->base.extend == CAIRO_EXTEND_NONE ||
gradient->base.type == CAIRO_PATTERN_TYPE_RADIAL))
{
double t[2];
_cairo_gradient_pattern_box_to_parameter (gradient,
extents->x,
extents->y,
extents->x + extents->width,
extents->y + extents->height,
DBL_EPSILON,
t);
if (gradient->base.extend == CAIRO_EXTEND_NONE &&
(t[0] >= gradient->stops[gradient->n_stops - 1].offset ||
t[1] <= gradient->stops[0].offset))
{
return TRUE;
}
if (t[0] == t[1])
return TRUE;
/* TODO: check actual intersection */
}
for (i = 0; i < gradient->n_stops; i++)
@ -2487,7 +2468,13 @@ _cairo_gradient_pattern_is_solid (const cairo_gradient_pattern_t *gradient,
if (extents == NULL)
return FALSE;
_extents_to_linear_parameter (linear, extents, t);
_cairo_linear_pattern_box_to_parameter (linear,
extents->x,
extents->y,
extents->x + extents->width,
extents->y + extents->height,
t);
if (t[0] < 0.0 || t[1] > 1.0)
return FALSE;
}
@ -2599,7 +2586,13 @@ _gradient_is_opaque (const cairo_gradient_pattern_t *gradient,
if (extents == NULL)
return FALSE;
_extents_to_linear_parameter (linear, extents, t);
_cairo_linear_pattern_box_to_parameter (linear,
extents->x,
extents->y,
extents->x + extents->width,
extents->y + extents->height,
t);
if (t[0] < 0.0 || t[1] > 1.0)
return FALSE;
}