GDでサムネイル生成

<?php

$dir  = 'test/';     //画像格納フォルダ
$file = 'test.png';  //画像ファイル名
$max  = 200;         //サムネイルのサイズ

if (preg_match('/\.gif$/i', $file)) {
    $image = imagecreatefromgif($dir . $file);
} elseif (preg_match('/\.(jpeg|jpg|jpe)$/i', $file)) {
    $image = imagecreatefromjpeg($dir . $file);
} elseif (preg_match('/\.png$/i', $file)) {
    $image = imagecreatefrompng($dir . $file);
}

$width  = imagesx($image);
$height = imagesy($image);

if ($width > $height) {
    if ($width > $max) {
    $new_width  = $max;
    $new_height = ($new_width / $width) * $height;
    } else {
    $new_width  = $width;
    $new_height = $height;
    }
} else {
    if ($height > $max) {
    $new_height = $max;
    $new_width  = ($new_height / $height) * $width;
    } else {
    $new_width  = $width;
    $new_height = $height;
    }
}

$new_image = imagecreatetruecolor($new_width, $new_height);

imagecopyresized($new_image, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);      //アンチエイリアスなし
//imagecopyresampled($new_image, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);  //アンチエイリアスあり

if (preg_match('/\.gif$/i', $file)) {
    imagegif($new_image, $dir . 'copy_of_' . $file);
} elseif (preg_match('/\.(jpeg|jpg|jpe)$/i', $file)) {
    imagejpeg($new_image, $dir . 'copy_of_' . $file, 70);
} elseif (preg_match('/\.png$/i', $file)) {
    imagepng($new_image, $dir . 'copy_of_' . $file);
}

imagedestroy($image);
imagedestroy($new_image);

?>

[/php]