PHP 縮圖

原文：http://webcache.googleusercontent.com/search?q=cache:EeR-EeFI5pUJ:blog.longwin.com.tw/2007/08/php_image_resize_2007/+&cd=1&hl=zh-TW&ct=clnk

/*
 * 抓取要縮圖的比例, 下述只處理 jpeg
 * $from_filename : 來源路徑, 檔名, ex: /tmp/xxx.jpg
 * $save_filename : 縮圖完要存的路徑, 檔名, ex: /tmp/ooo.jpg
 * $in_width : 縮圖預定寬度
 * $in_height: 縮圖預定高度
 * $quality  : 縮圖品質(1~100)
 *
 * Usage:
 *   ImageResize('ram/xxx.jpg', 'ram/ooo.jpg');
 */
function ImageResize($from_filename, $save_filename, $in_width, $in_height, $quality)
{
    $allow_format = array('jpeg', 'png', 'gif');
    $sub_name = $t = '';
    
    // Get new dimensions
    $img_info = getimagesize($from_filename);
    $width    = $img_info['0'];
    $height   = $img_info['1'];
    $imgtype  = $img_info['2'];
    $imgtag   = $img_info['3'];
    $bits     = $img_info['bits'];
    $channels = $img_info['channels'];
    $mime     = $img_info['mime'];

    $in_width = ($in_width == '') ? $width : $in_width;
    $in_height = ($in_height == '') ? $height : $in_height;
    $quality = ($quality == '') ? 100 : $quality;
    
    list($t, $sub_name) = split('/', $mime);
    if ($sub_name == 'jpg') {
        $sub_name = 'jpeg';
    }

    if (!in_array($sub_name, $allow_format)) {
        return false;
    }

    // 取得縮在此範圍內的比例
    $percent = getResizePercent($width, $height, $in_width, $in_height);
    $new_width  = $width * $percent;
    $new_height = $height * $percent;
    /*
     * echo "from_filename = ".$from_filename."
";
     * echo "width = ".$width."
";
     * echo "height = ".$height."
";
     * echo "in_width = ".$in_width."
";
     * echo "in_height = ".$in_height."
";
     * echo "percent = ".$percent."
";
     */
    // Resample
    $image_new = imagecreatetruecolor($new_width, $new_height);

    // $function_name: set function name
    //   => imagecreatefromjpeg, imagecreatefrompng, imagecreatefromgif
    /*
    // $sub_name = jpeg, png, gif
    $function_name = 'imagecreatefrom' . $sub_name;

    if ($sub_name=='png')
        return $function_name($image_new, $save_filename, intval($quality / 10 - 1));

    $image = $function_name($filename); //$image = imagecreatefromjpeg($filename);
    */
    $image = imagecreatefromjpeg($from_filename);

    imagecopyresampled($image_new, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);

    return imagejpeg($image_new, $save_filename, $quality);
}

/**
 * 抓取要縮圖的比例
 * $source_w : 來源圖片寬度
 * $source_h : 來源圖片高度
 * $inside_w : 縮圖預定寬度
 * $inside_h : 縮圖預定高度
 *
 * Test:
 *   $v = (getResizePercent(1024, 768, 400, 300));
 *   echo 1024 * $v . "\n";
 *   echo  768 * $v . "\n";
 */
function getResizePercent($source_w, $source_h, $inside_w, $inside_h)
{
    if ($source_w < $inside_w && $source_h < $inside_h) {
        return 1; // Percent = 1, 如果都比預計縮圖的小就不用縮
    }

    $w_percent = $inside_w / $source_w;
    $h_percent = $inside_h / $source_h;

    return ($w_percent > $h_percent) ? $h_percent : $w_percent;
}
?>