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(PECL cairo >= 0.1.0)
CairoContext::curveTo -- cairo_curve_to — Adds a curve
面向对象风格 (method):
$x1 
   ,  float $y1 
   ,  float $x2 
   ,  float $y2 
   ,  float $x3 
   ,  float $y3 
    )过程化风格:
$context 
   ,  float $x1 
   ,  float $y1 
   ,  float $x2 
   ,  float $y2 
   ,  float $x3 
   ,  float $y3 
   )
   Adds a cubic Bezier spline to the path from the current point to position x3
   ,y3 in user-space coordinates, using x1,
   y1 and x2, y2 as the control
   points. After this call the current point will be x3, y3.
  
    If there is no current point before the call to  CairoContext::curveTo() 
    this function will behave as if preceded by a call to  CairoContext::moveTo() 
    (x1, y1).
  
context A valid CairoContext object created with CairoContext::__construct() or cairo_create()
x1 First control point in the x axis for the curve
y1 First control point in the y axis for the curve
x2 Second control point in x axis for the curve
y2 Second control point in y axis for the curve
x3 Final point in the x axis for the curve
y3 Final point in the y axis for the curve
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 -> moveTo ( 10 ,  50 ); 
 $c -> setLineWidth ( 5 );
 $c -> setSourceRgb ( .1 ,  0 ,  1 );
 $c -> curveTo ( 20 ,  80 ,  80 ,  20 ,  90 ,  50 ); 
 $c -> stroke ();
 $s -> writeToPng ( dirname ( __FILE__ ) .  '/curveTo.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_move_to ( $c ,  10 ,  50 );
 cairo_set_line_width ( $c ,  5 );
 cairo_set_source_rgb ( $c ,  .1 ,  0 ,  1 );
 cairo_curve_to ( $c ,  20 ,  80 ,  80 ,  20 ,  90 ,  50 );
 cairo_stroke ( $c );
 cairo_surface_write_to_png ( $s ,  dirname ( __FILE__ ) .  '/curve_to.png' );
 ?>