[php-src] Issue #13379: imagearc bug

Issue: https://github.com/php/php-src/issues/13379 Author: erroneum When using imagearc along with imagesetthickness for a thickness value larger than 1, there are graphical anomalies, most notably at the locations 45° off axis. I've verified this to still be an issue as recently as PHP version 8.1.2 and GD version 2.3.0 I suspect that the issue stems from the algorithm being used to plot the circular arcs (I suspect derived from the midpoint circle algorithm) failing to correctly fill in as it reaches the terminal case. I do not know if that would put it as something the PHP module handles or something implemented in libGD itself. Here is an image showing what I'm talking about  And the code which generated the issue: ```php <?php $x = $y = 2000; $i = imagecreatetruecolor ( $x, $y ); $white = imagecolorallocate ( $i, 255, 255, 255 ); imagefill ( $i, 0, 0, $white ); imagesetthickness ( $i, $x * 0.025 ); $c = imagecolorallocate ( $i, 0xC4, 0xC4, 0xC4 ); imagearc ( $i, $x / 2, $y / 2, $x * 0.8, $y * 0.8, 0, 360, $c ); imagepng ( $i, 'gdarc.png' ); ```