# cairo_arc

(PECL cairo >= 0.1.0)

CairoContext::arc -- cairo_arcAdds a circular arc

### Descrizione

Stile orientato agli oggetti (method):

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

Stile procedurale:

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.

### Elenco dei parametri

`context`

A valid CairoContext object

`x`

x position

`y`

y position

`radius`

`angle1`

start angle

`angle2`

end angle

### Valori restituiti

Nessun valore viene restituito.

### Esempi

Example #1 Stile orientato agli oggetti

``` <?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 Stile procedurale

``` <?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');?> ```