CairoContext
PHP Manual

CairoContext::arc

cairo_arc

Adds a circular arc

Description

Object oriented style (method):

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

Procedural style:

void cairo_arc ( CairoContext $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.

Parameters

context

A valid CairoContext object

x

x position

y

y position

radius

Radius of the arc

angle1

start angle

angle2

end angle

Return Values

No value is returned.

Examples

Example #1 Object oriented style

<?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 Procedural style

<?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');
?>

See Also

  • CairoContext::arcNegative