imagepolygon()

(PHP 4, PHP 5, PHP 7)

画一个多边形

说明

imagepolygon(resource $image,array $points,int $num_points,int $color): bool

imagepolygon()在图像中创建一个多边形。$points是一个 PHP 数组，包含了多边形的各个顶点坐标，即 points[0]= x0，points[1]= y0，points[2]= x1，points[3]= y1，以此类推。$num_points是顶点的总数。

imagepolygon()例子

<?php
// create a blank image
$image = imagecreatetruecolor(400, 300);
// fill the background color
$bg = imagecolorallocate($image, 0, 0, 0);
// choose a color for the polygon
$col_poly = imagecolorallocate($image, 255, 255, 255);
// draw the polygon
imagepolygon($image,
             array (
                    0, 0,
                    100, 200,
                    300, 200
             ),
             3,
             $col_poly);
// output the picture
header("Content-type: image/png");
imagepng($image);
?>

参见imagecreate()和imagecreatetruecolor()。

Function to get 5-sided polygon (pentagon) or star (pentagram) co-ords. 
<?php
function _makeFiveSidedStar( $x, $y, $radius, $shape='polygon', $spiky=NULL ) {
  $point = array() ; // new array                                                          
  $angle = 360 / 5 ;                                                          
  $point[0]['x'] = $x ;                                                         
  $point[0]['y'] = $y - $radius ;                                                    
  $point[2]['x'] = $x + ( $radius * cos( deg2rad( 90 - $angle ) ) ) ; 
  $point[2]['y'] = $y - ( $radius * sin( deg2rad( 90 - $angle ) ) ) ;
  $point[4]['x'] = $x + ( $radius * sin( deg2rad( 180 - ( $angle*2 ) ) ) ) ;
  $point[4]['y'] = $y + ( $radius * cos( deg2rad( 180 - ( $angle*2 ) ) ) ) ;
  $point[6]['x'] = $x - ( $radius * sin( deg2rad( 180 - ( $angle*2 ) ) ) ) ;                              
  $point[6]['y'] = $y + ( $radius * cos( deg2rad( 180 - ( $angle*2 ) ) ) ) ;
  $point[8]['x'] = $x - ( $radius * cos( deg2rad( 90 - $angle ) ) ) ;                                  
  $point[8]['y'] = $y - ( $radius * sin( deg2rad( 90 - $angle ) ) ) ;
  if( $shape == 'star' ) {
    if( $spiky == NULL ) $spiky = 0.5 ; // degree of spikiness, default to 0.5
    $indent = $radius * $spiky ;
    $point[1]['x'] = $x + ( $indent * cos( deg2rad( 90 - $angle/2 ) ) ) ;                               
    $point[1]['y'] = $y - ( $indent * sin( deg2rad( 90 - $angle/2 ) ) ) ;                           
    $point[3]['x'] = $x + ( $indent * sin( deg2rad( 180 - $angle ) ) ) ;                               
    $point[3]['y'] = $y - ( $indent * cos( deg2rad( 180 - $angle ) ) ) ;
    $point[5]['x'] = $x ;                                                       
    $point[5]['y'] = $y + ( $indent * sin( deg2rad( 180 - $angle ) ) ) ;
    $point[7]['x'] = $x - ( $indent * sin( deg2rad( 180 - $angle ) ) ) ;                               
    $point[7]['y'] = $y - ( $indent * cos( deg2rad( 180 - $angle ) ) ) ;                               
    $point[9]['x'] = $x - ( $indent * cos( deg2rad( 90 - $angle/2 ) ) ) ;                               
    $point[9]['y'] = $y - ( $indent * sin( deg2rad( 90 - $angle/2 ) ) ) ;
  }
  ksort( $point ) ;
  $coords = array() ; // new array                                                         
  foreach( $point as $pKey=>$pVal ) {                                                  
    if( is_array( $pVal ) ) {                                                     
      foreach( $pVal as $pSubKey=>$pSubVal ) {                                           
        if( !empty( $pSubVal ) ) array_push( $coords, $pSubVal ) ;                                
      }                                                               
    }                                                                 
  }
  return $coords ;
}
$values = _makeFiveSidedStar( 100, 100, 50, 'star' ) ;
?>

Function to draw a n-sided regular polygon
<?php
$img = imagecreatetruecolor(1360,768);
function regularPolygon($img,$x,$y,$radius,$sides,$color)
{
  $points = array();
  for($a = 0;$a <= 360; $a += 360/$sides)
  {
    $points[] = $x + $radius * cos(deg2rad($a));
    $points[] = $y + $radius * sin(deg2rad($a));
  }
  return imagepolygon($img,$points,$sides,$color);
}
regularPolygon($img,1360/2,768/2,300,8,0xffffff);//Test draw
header('Content-type: image/png');
imagepng($img);
imagedestroy($img);
?>

Here are some handy routines for rotation and translation of polygons. Scaling could be added easily as well.
<?php
function translate_point(&$x,&$y,$angle,$about_x,$about_y,$shift_x,$shift_y)
{
  $x -= $about_x;
  $y -= $about_y;
  $angle = ($angle / 180) * M_PI;
/* math:
[x2,y2] = [x, * [[cos(a),-sin(a)],
      y]   [sin(a),cos(a)]]
==>
x = x * cos(a) + y*sin(a) 
y = x*-sin(a) + y*cos(a)
*/
  $new_x = $x * cos($angle) - $y * sin($angle);
  $new_y = $x * sin($angle) + $y * cos($angle);
  $x = $new_x+ $about_x + $shift_x ;
  $y = $new_y + $about_y + $shift_y;
}
function translate_poly($point_array, $angle, $about_x, $about_y,$shift_x,$shift_y)
{
  $translated_poly = Array();
  while(count($point_array) > 1)
  {
    $temp_x = array_shift($point_array);
    $temp_y = array_shift($point_array);
    translate_point($temp_x, $temp_y, $angle, $about_x, $about_y,$shift_x, $shift_y);
    array_push($translated_poly, $temp_x);
    array_push($translated_poly, $temp_y);
  }
  return $translated_poly;
}
?>

Here's a function to draw a n-sided star:
<?php
function drawStar($img,$x,$y,$radius,$sides,$color,$spikness=0.5)
{
  $point =array();
  $t = 0;
  for($a = 0;$a <= 360;$a += 360/($sides*2))
  {
    $t++;
    if($t % 2 == 0)
    {
      $point[] = $x + ($radius * $spikness) * cos(deg2rad($a));
      $point[] = $y + ($radius * $spikness) * sin(deg2rad($a));
    }else{
      $point[] = $x + $radius * cos(deg2rad($a));
      $point[] = $y + $radius * sin(deg2rad($a));
    }
  }
  return imagepolygon($img,$point,$sides*2,$color);
}
?>