Here's a little function I wrote to resize images to a maximum dimension - based on what facebook does in the galleries. You put in a source, destination and a maximum dimension in pixels (eg 300), and for example if the image is long and thin, the longest edge will be 300px, yet the image retains proportions. A square image will become 300x300, a 6x4 (landscape) will become 300x200, a 4x6 (portrait) - 200x300 etc.
It works on jpg images, but other formats can easily be added.
<?php
function createThumb($spath, $dpath, $maxd) {
$src=@imagecreatefromjpeg($spath);
if (!$src) {return false;} else {
$srcw=imagesx($src);
$srch=imagesy($src);
if ($srcw<$srch) {$height=$maxd;$width=floor($srcw*$height/$srch);}
else {$width=$maxd;$height=floor($srch*$width/$srcw);}
if ($width>$srcw && $height>$srch) {$width=$srcw;$height=$srch;} $thumb=imagecreatetruecolor($width, $height);
if ($height<100) {imagecopyresized($thumb, $src, 0, 0, 0, 0, $width, $height, imagesx($src), imagesy($src));}
else {imagecopyresampled($thumb, $src, 0, 0, 0, 0, $width, $height, imagesx($src), imagesy($src));}
imagejpeg($thumb, $dpath);
return true;
}
}
?>
