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    /*  Convert image size. true color*/
    //$src        來源檔案
    //$dest        目的檔案
    //$maxWidth    縮圖寬度
    //$maxHeight    縮圖高度
    //$quality    JPEG品質
    function ImageCopyResizedTrue($src,$dest,$maxWidth,$maxHeight,$quality=100) {
        //檢查檔案是否存在
        if (file_exists($src)  && isset($dest)) {
            $destInfo  = pathInfo($dest);
            $srcSize   = getImageSize($src); //圖檔大小
            $srcRatio  = $srcSize[0]/$srcSize[1]; // 計算寬/高
            $destRatio = $maxWidth/$maxHeight;
            if ($destRatio > $srcRatio) {
                $destSize[1] = $maxHeight;
                $destSize[0] = $maxHeight*$srcRatio;
            }
            else {
                $destSize[0] = $maxWidth;
                $destSize[1] = $maxWidth/$srcRatio;
            }
            //GIF 檔不支援輸出，因此將GIF轉成JPEG
            if ($destInfo['extension'] == "gif") $dest = substr_replace($dest, 'jpg', -3);
            //建立一個 True Color 的影像
            $destImage = imageCreateTrueColor($destSize[0],$destSize[1]);
            //根據副檔名讀取圖檔
            switch ($srcSize[2]) {
                case 1: $srcImage = imageCreateFromGif($src); break;
                case 2: $srcImage = imageCreateFromJpeg($src); break;
                case 3: $srcImage = imageCreateFromPng($src); break;
                default: return false; break;
            }
            //取樣縮圖
            ImageCopyResampled($destImage, $srcImage, 0, 0, 0, 0,$destSize[0],$destSize[1],
                                $srcSize[0],$srcSize[1]);
            //輸出圖檔
            switch ($srcSize[2]) {
                case 1: case 2: imageJpeg($destImage,$dest,$quality); break;
                case 3: imagePng($destImage,$dest); break;
            }
            return true;
        }
        else {
            return false;
        }
    }
?>

<?
    //呼叫縮圖函式
    ImageCopyResizedTrue("pict1.jpg","pict1s.jpg",400,300);
?>