The following is potentially useful. It extracts the central largest circle of an image into a square of specified size, and optionally rotates it. The rest of the square is made transparent, so useful for drawing over other images. I've named it after binocular effect because on some old TV shows whenever they show someone looking through binoculars the screen shows a big circular image with black edges.
<?php
function image_binocular_effect($src, $bearing, $out_square) {
$out = imagecreatetruecolor($out_square, $out_square);
$width=imagesx($src);
$height=imagesy($src);
$square=min($width, $height);
imagecopyresampled($out, $src, 0, 0, ($width - $square)/2 , ($height - $square)/2, $out_square, $out_square, $square, $square);
$mask = imagecreatetruecolor($out_square, $out_square);
$black = ImageColorAllocate ($mask, 0, 0, 0);
$white = ImageColorAllocate ($mask, 255, 255, 255);
imagefilledrectangle($mask , 0, 0, $out_square, $out_square, $white);
$centrexy=$out_square / 2;
imagefilledellipse($mask, $centrexy, $centrexy, $out_square, $out_square, $black);
ImageColorTransparent($mask, $black);
imagecopymerge($out, $mask, 0, 0, 0, 0, $out_square, $out_square, 100);
if ($bearing != 0) {
$rotated_img=imagerotate($out , 360-$bearing, $white);
$rotated_map_width = imagesx($rotated_img);
$rotated_map_height = imagesy($rotated_img);
imagecopy($out, $rotated_img, 0, 0, ($rotated_map_width - $out_square) / 2, ($rotated_map_height - $out_square) / 2, $out_square, $out_square);
}
ImageColorTransparent($out, $white);
return $out;
}
$src = imagecreatetruecolor(200, 50);
imagefilledrectangle($src, 0, 0, 200, 50, imagecolorallocate($src, 255, 255, 255));
ImageString($src, 3, 10, 10, "This is a sample image to illustrate the binocular effect", imagecolorallocate($im, 192, 0, 0));
$img=image_binocular_effect($src, 72, 50);
ImagePNG($img,"test.png");
?>
