CairoContext::arc()

(PECL cairo >= 0.1.0)

Adds a circular arc

说明

面向对象风格(method):

publicCairoContext::arc(float $x,float $y,float $radius,float $angle1,float $angle2): void

过程化风格:

cairo_arc(CairoContext$context,float $x,float $y,float $radius,float $angle1,float $angle2): void

Adds a circular arc of the given radius to the current path. The arc is centered at($x,$y), begins at$angle1and proceeds in the direction of increasing angles to end at$angle2. If$angle2is less than$angle1it 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.

参数

$context: A valid CairoContext object
$x: x position
$y: y position
$radius: Radius of the arc
$angle1: start angle
$angle2: end angle

返回值

没有返回值。

范例

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');
?>

参见

CairoContext::arcNegative() Adds a negative arc