php图片缩放实现方法

<?php
??? /**
??? * image zoom.
??? */
??? function imageZoom($filename, $w, $h) {
??????? /* Arguments meaning */
??????? /* $filename: the source of the name */
??????? /* $w: you want get the image's width */
??????? /* $h: you want get the imgage's height */
??????? $arr = getimagesize($filename);
??????? $src_w = $arr[0];
??????? $src_h = $arr[1];
??????? $src_t = $arr[2];
??????? /*1 = GIF，2 = JPG，3 = PNG，4 = SWF，5 = PSD，6 = BMP，7 = TIFF(intel byte order)，
= TIFF(motorola byte order)，9 = JPC，10 = JP2，11 = JPX，12 = JB2，13 = SWC，
= IFF，15 = WBMP，16 = XBM*/
??????? $src_m = $arr['mime'];

?

??????? $src_img = imagecreatefromjpeg($filename);

??????? if (($w / $src_w) >($h / $src_h)) {
??????????? $bili = $h / $src_h;
??????? } else {
??????????? $bili = $w / $src_h;
??????? }
??????? $dst_w = $src_w * $bili;
??????? $dst_h = $src_h * $bili;
??????? $dst_img = imagecreatetruecolor($dst_w, $dst_h);

??????? imagecopyresampled($dst_img, $src_img, 0, 0, 0, 0, $dst_w, $dst_h, $src_w, $src_h);

??????? header("content-type:{$src_m}");

??????? switch ($src_t) {
??????????? case 1:
??????????????? $imgout = "imagegif";
??????????????? break;
??????????? case 2:
??????????????? $imgout = "imagejpeg";
??????????????? break;
??????????? case 3:
??????????????? $imgout = "imagepng";
??????????????? break;
??????????? default:
??????????????? echo "The type was wrong!";
??????????????? break;
??????? }

??????? $dst_filename = "s_".$filename;
??????? $imgout($dst_img, $dst_filename);

??????? imagedestroy($dst_img);
??? }
??? $filename = 'gg.jpg';
??? imageZoom($filename, 100, 200);