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Date: Sat, 21 Jan 2017 18:42:07 +0100
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Subject: =?UTF-8?Q?imagepolygon=28=29_=e2=80=93_number_of_points?=
From: cmbecker69@gmx.de ("Christoph M. Becker")

Hi!

This issue has been filed to our bugtracker years ago[1], but didn't
deserve much attention, so I'm forwarding to the list.

imagepolygon(), imagefilledpolygon() and imageopenpolygon() have the
following signature:

  image*polygon(resource $im, array $points, int $num_points, int $col)

Note the third parameter, $num_points, which doesn't make much sense for
PHP, and has most likely being directly ported from the underlying libgd
implementation of gdImage*Polygon[2].

Even worse, while the common implementation[3] checks that $points
(which would better have been called $coordinate, by the way) has at
least 6 elements, $num_points can be smaller than 3, what will cause
gdImage*Polygon() to be called with only so many points.  That is not an
issue per se, as gdImage*Polygon() is capable of handling monogons and
digons, but of course it doesn't make sense to force the programmer to
construct a larger array with unused values to do so.  Furthermore the
imagefilledpolygon() man page[4] states that $num_points must be greater
than or equal to 3, but neither of the other man pages document this.

In the long run (i.e. for PHP 8) I'd suggest to purge the $num_points
parameter altogether, relying solely on the number of $points given.

For PHP 7.2 I propose to weaken the constraint on count($points) so that
2 would be sufficient instead of the 6 required now.

Would the proposed change for PHP 7.2 require an RFC, or would a PR suffice?

[1] <https://bugs.php.net/bug.php?id=55005>
[2] <http://libgd.github.io/manuals/2.2.4/files/gd-c.html#gdImagePolygon>
[3] <https://github.com/php/php-src/blob/PHP-7.1.1/ext/gd/gd.c#L3355-L3413>
[4] <http://php.net/manual/en/function.imagefilledpolygon.php>

-- 
Christoph M. Becker