(PECL cairo >= 0.1.0)
CairoContext::arc -- cairo_arc — Adds a circular arc
面向对象风格 (method):
$x
, float $y
, float $radius
, float $angle1
, float $angle2
)过程化风格:
$context
, float $x
, float $y
, float $radius
, float $angle1
, float $angle2
)
Adds a circular arc of the given radius to the current path.
The arc is centered at (x, y), begins at
angle1 and proceeds in the direction of increasing angles to end at
angle2.
If angle2 is less than angle1 it will be
progressively increased by 2*M_PI until it is greater than angle1.
If there is a current point, an initial line segment will be added to the path to connect the
current point to the beginning of the arc. If this initial line is undesired,
it can be avoided by calling CairoContext::newSubPath() or procedural
cairo_new_sub_path() before calling CairoContext::arc()
or cairo_arc().
Angles are measured in radians. An angle of 0.0 is in the direction of the positive X axis
(in user space). An angle of M_PI/2.0 radians (90 degrees) is in the direction of the positive
Y axis (in user space). Angles increase in the direction from the positive X axis toward the
positive Y axis. So with the default transformation matrix, angles increase in a clockwise direction.
(To convert from degrees to radians, use degrees * (M_PI / 180.).)
This function gives the arc in the direction of increasing angles; see
CairoContext::arcNegative() or cairo_arc_negative()
to get the arc in the direction of decreasing angles.
contextA valid CairoContext object
xx position
yy position
radiusRadius of the arc
angle1start angle
angle2end angle
没有返回值。
Example #1 面向对象风格
<?php
$s = new CairoImageSurface(CairoFormat::ARGB32, 100, 100);
$c = new CairoContext($s);
$c->setSourceRgb(0, 0, 0);
$c->paint();
$c->setLineWidth(1);
$c->setSourceRgb(1, 1, 1);
for ($r = 50; $r > 0; $r -= 10) {
$c->arc(50, 50, $r, 0, 2 * M_PI);
$c->stroke();
$c->fill();
}
$s->writeToPng(dirname(__FILE__) . '/CairoContext__arc.png');
?>
Example #2 过程化风格
<?php
$s = cairo_image_surface_create(CAIRO_SURFACE_TYPE_IMAGE, 100, 100);
$c = cairo_create($s);
cairo_set_source_rgb($c, 0, 0, 0);
cairo_paint($c);
cairo_set_source_rgb($c, 1, 1, 1);
cairo_set_line_width($c, 1);
for ($r = 50; $r > 0; $r -= 10) {
cairo_arc($c, 50, 50, $r, 0, 2 * M_PI);
cairo_stroke($c);
cairo_fill($c);
}
cairo_surface_write_to_png($s, dirname(__FILE__) . '/cairo_arc.png');
?>