我的'.png'图片无法用于调整php中​​的图像代码

Question

when i pass a jpg file to imgsize.php?w=100&h=100&img=powered_by.jpg then its work well but i pass a png file to imgsize.php?w=100&h=100&img=mengo.png it's not working

my imgsize.php file code is

$extension = pathinfo($_GET['img']);
$extension = $extension[extension];
if ($extension == "jpg" || $extension == "jpeg" || $extension == "JPG") {
    header("Content-type: image/jpeg");
}
if ($extension == "png") {
    header("Content-type: image/png");
}
if ($extension == "gif") {
    header("Content-type: image/gif");
}
$img     = $_GET['img'];
$nwidth  = $_GET['w'];
$nheight = $_GET['h'];
$img2    = imagecreatefromjpeg($_GET['img']);
$width   = imagesx($img2);
$height  = imagesy($img2);
$ratio   = $width / $height;
$new_nwidth  = $nwidth;
$new_nheight = floor($height * ($nwidth / $width));
$im = imagecreatefromjpeg($img) or $im = imagecreatefrompng($img) or $im = imagecreatefromgif($img) or $im = false;
if (!$im) {
} else {
    $thumb = imagecreatetruecolor($new_nwidth, $new_nheight);
    imagealphablending($thumb, false);
    imagesavealpha($thumb, true);
    $transparent = imagecolorallocatealpha($thumb, 255, 255, 255, 127);
    imagefilledrectangle($thumb, 0, 0, $new_nwidth, $new_nheight, $transparent);
    imagecopyresized($thumb, $im, 0, 0, 0, 0, $new_nwidth, $new_nheight, $width, $height);
    if ($extension == "jpg" || $extension == "jpeg" || $extension == "JPG") {
        imagejpeg($thumb, null, 100);
    }
    if ($extension == "png") {
        imagepng($thumb, null, 9);
    }
    if ($extension == "gif") {
        imagegif($thumb, null, 100);
    }
}

any solution for it ? its display blank image when i pass it out a png file

Answer 1

As you have checked for the extension in if else condition to generate header the same way you would have to check for creating $img2 like

if ($extension == "jpg" || $extension == "jpeg" || $extension == "JPG") {
    $img2    = imagecreatefromjpeg($_GET['img']);
}
if ($extension == "png") {
    $img2    = imagecreatefrompng($_GET['img']);
}
if ($extension == "gif") {
    $img2    = imagecreatefromgif($_GET['img']);
}

One another thing i would like to add for your info is that check for image mime type rather that checking extension. for that you can user getimagesize function, which return an array and you can check for mime type by $retun_array['mime'].

PNG images often creates problem if not created or stored properly. Corrupt images may cause this problem too. Hope this may work for you.

Answer 2

I leave you my code for thumbnail images and save them into a destination folder

    function thumbail($forcedwidth, $forcedheight, $sourcefile, $destfile){
    $fw = $forcedwidth;
    $fh = $forcedheight;
    $is = getimagesize( $sourcefile );
    $ancho = $is[0];
    $alto = $is[1];
    if($ancho > $forcedwidth) { 
        $ancho2 = $forcedwidth;
        $por = (100 * $forcedwidth)/$ancho;
        $alto2 = ($alto * $por)/100;
        $t = 1;
    }else{
        $ancho2 = $ancho;
        $alto2 = $alto;
        $t = 2;
    }

    if($alto > $forcedheight) { 
        $alto2 = $forcedheight;
        $por = (100 * $forcedheight)/$alto;
        $ancho2 = ($ancho * $por)/100;
        $t = 1;
    }else{
        $ancho2 = $ancho;
        $alto2 = $alto;
    }
    if ($t == 1){
        $img_src = imagecreatefromjpeg( $sourcefile );
        $img_dst = imagecreatetruecolor( $ancho2, $alto2 );
        imagecopyresampled( $img_dst, $img_src, 0, 0, 0, 0, $ancho2, $alto2, $is[0], $is[1] );
        if(!imagejpeg($img_dst, $destfile, 90 )){
            exit();
        }
    }else if ($t == 2){
        copy( $sourcefile, $destfile );
    }
}