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"Creating filled polygons with PHP"

Hi. I ripped and edited this code from the PHP.net site to make a filled polygon from a set of variables posted through a form:

$values = array(
0 => $a_x, // x1
1 => $a_y, // y1
2 => $b_x, // x2
3 => $b_y, // y2
4 => $c_x, // x3
5 => $c_y, // y3
6 => $d_x, // x4
7 => $d_y, // y4
);
$im = imagecreate(500, 500);
$bg = imagecolorallocate($im, 255, 255, 255);
$blue = imagecolorallocate($im, 0, 0, 255);
imagefilledpolygon($im, $values, 4, $blue );
?>

But surprise, surprise, it doesn't work for me. I don't get any error messages though. Any ideas?

Yeah, that makes sense! I'm such a duuuur brain.

monkey_man wrote:
> Yeah, I changed the colours around on purpose just to make sure that
> the imagecreate was working. It doesn't matter about that for now.
> When assigning the variables, can it be done straight from the posted
> form, or do I need to post to another variable and then use that
> within the array?

Well, you need to post the variables to image.php, something like


(of course with all your vars)

just checking and the array does work with my own numbers, just not the posted variables...

I don't need to "print" the variables, do I?

Yeah, I changed the colours around on purpose just to make sure that the imagecreate was working. It doesn't matter about that for now. When assigning the variables, can it be done straight from the posted form, or do I need to post to another variable and then use that within the array?

Well, first thing, I notice you've inverted your colours, ie blue background and filling the polygon with white, which is why you have a blue box and nothing in it. But besides the point at present.

In your image.php file how are the values in the array being assigned? At the moment, they map to variables, $a_x, $a_y etc. but you're not showing any assignment of them. The array itself is fine, and you are using it in the right manner with ImageFilledPolygon. If you replace $a_x etc. with your own numbers, it does work so presumably your variables aren't being assigned.

Hmmm. Now I have this for image.php:

Header ("Content-type: image/png");
$values = array(
0 => $a_x,
1 => $a_y,
2 => $b_x,
3 => $b_y,
4 => $c_x,
5 => $c_y,
6 => $d_x,
7 => $d_y, );
$im = Imagecreate(500, 500);
$bg = ImageColorAllocate($im, 0, 0, 255);
$blue = ImageColorAllocate($im, 255, 255, 255);
ImageFilledPolygon($im, $values, 4, $blue );
ImagePng ($im);
ImageDestroy ($im); ?>

Then a php file that has the content "".

But I still get just a blue box, which leads me to deduce, with my Columbo-esque superpowers that it's something to do with how the variables are being fed through. Can anyone see a problem with what I'm doing for the array?

OK, I've done as you've suggested and it actually creates an image! But the polygon doesn't appear at all. It's just a blank white image.

Make sure there are no spaces at the top or bottom of your source, outside of the php tags.

Hm, ok..

The code to create the image should be in a separate file called image.php or whatever, which should then be called via an image link in the page you want it displayed on e.g.

OK, now I have this:

$values = array(
0 => $a_x,
1 => $a_y,
2 => $b_x,
3 => $b_y,
4 => $c_x,
5 => $c_y,
6 => $d_x,
7 => $d_y, );
$im = Imagecreate(500, 500);
$bg = ImageColorAllocate($im, 255, 255, 255);
$blue = ImageColorAllocate($im, 0, 0, 255);
ImageFilledPolygon($im, $values, 4, $blue );
ImagePng ($im);
ImageDestroy ($im);
?>
">

All the breaks are taken out in the uploaded code, so it's one big line of text. I get a broken image and still gibberish underneath. Is there anything wrong with the fundamentals of this, or is it something secret that only FREEOLA would know?