PHP: imagepolygon

Description

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

imagepolygon() creates a polygon in image id. points is a PHP array containing the polygon's vertices, i.e. points[0] = x0, points[1] = y0, points[2] = x1, points[3] = y1, etc. num_points is the total number of points (vertices).

Пример 1. imagepolygon() example

<?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); ?>

imagepolygon

glowell at flash dot net
17-Nov-2005 03:43


Something to be aware of, ImagePolygon appears to convert the array of points passed to it from whatever format they may have been in originally into integers. This means if you pass it an array of floats (after running a rotation routine for example) the floats will be changed to integers INSIDE THE ORIGINAL ARRAY.



An extreme example: if for some reason you had an unit-sized polygon pt-array ( -1<x|y<1 for easy scaling purpose for instance) and for some reason your code calls imagepolygon on it (why? it'd only be a dot anyway) the array would be unusable after that (all either 1s, 0s or -1s). Scaling a unit-sized array, drawing it and then scaling it again will also may have a different result than expected.



Obviously, if the array in its original state is important to your code, it should use a copy of the original array for this call. If your code draws the same polygon multiple times but resizes it for different cases, you should have each size be created off an original template rather than adjusting a single polygon array.

jsnell at networkninja dot com
17-Feb-2001 07:07


Here are some handy routines for rotation and translation of polygons.  Scaling could be added easily as well.





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;


}