PHP　GDでリサイズした時の背景色

GDでリサイズした時に背景が黒になってしまいます
これを透明にできますか？
いろいろ調べてみてもわかりませんでした

php
1
2if (isset($_POST["send"])) {
3    $file = $_FILES['fname']['tmp_name'];
4
5    
6    $date= getimagesize($file);
7
8    
9    list($width, $hight)=$date;
10
11    if ($width <= 100 && $hight <= 200) {
12        $nw = $width;
13        $nh = $hight;
14    }
15    else{
16        $w = $width / 100;
17        $h = $hight / 200;
18
19        if ($w > $h) {
20            $nw = $width / $w;
21            $nh = $hight / $w;
22        } elseif ($w < $h) {
23            $nw = $width / $h;
24            $nh = $hight / $h;
25        }
26    
27        var_dump($nw);
28        var_dump($nh);
29        $nx = (100-$nw) / 2;
30        $ny = (200-$nh) / 2;
31    }
32   
33
34    //JPG
35    if ($date[2] == 2) {
36    $img_in = imagecreatefromjpeg($file);
37    $img_out = imagecreatetruecolor(100, 200);
38
39    imagealphablending($img_out, false);
40    imagesavealpha($img_out, true);
41
42
43    
44    imagecopyresampled($img_out, $img_in, $nx, $ny, 0, 0, $nw, $nh, $width, $hight);
45    
46    $filename = 'jpeg';
47
48    imagejpeg($img_out, "images/new.jpeg");
49    }
50    
51//PNG
52    elseif ($date[2] == 3) {
53
54        $img_in = imagecreatefrompng($file);
55        $img_out = imagecreatetruecolor(100, 200);
56
57
58
59        imagealphablending($img_out, false);
60        imagesavealpha($img_out, true);
61        
62
63
64        imagecopyresampled($img_out, $img_in, $nx, $ny, 0, 0, $nw, $nh, $width, $hight);
65
66        
67 
68    
69        $filename = 'png';
70        
71        imagepng($img_out, 'images/new.png');
72    }
73
74
75    //GIF
76    elseif($date[2] == 1){
77        $img_in = imagecreatefromgif($file);
78        $img_out = imagecreatetruecolor(100, 200);
79
80        imagealphablending($img_out, false);
81        imagesavealpha($img_out, true);
82    
83    
84        imagecopyresampled($img_out, $img_in, $nx, $ny, 0, 0, $nw, $nh, $width, $hight);
85    
86
87        $filename = 'gif';
88        imagegif($img_out, "images/new.gif");
89    }
90
91
92        
93    imagedestroy($img_in);
94    imagedestroy($img_out);

html
1<form action="" method="post" enctype="multipart/form-data">
2  <input type="file" name="fname">
3  <input type="submit" value="アップロード" name="send">
4</form>
5<?php if(isset($img_out) && $filename == 'jpeg'){
6    echo '<p><img src="images/new.jpeg" alt=""></p>';
7    } ?>
8
9<?php if(isset($img_out) && $filename == 'png'){
10    echo '<p><img src="images/new.png" alt=""></p>';
11    } ?>
12<?php if(isset($img_out) && $filename == 'gif'){
13    echo '<p><img src="images/new.gif" alt=""></p>';
14    } ?>