我的'.png'图片无法用于调整php中​​的图像代码

Question

当我将jpg文件传递给imgsize.php?w=100&h=100&img=powered_by.jpg时，它的工作正常 但我将一个png文件传递给imgsize.php?w=100&h=100&img=mengo.png它无法正常工作

我的imgsize.php文件代码是

$extension = pathinfo($_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);
    }
}

任何解决方案吗？当我将它传递出一个png文件时，它显示空白图像

Answer 1

正如您在if else条件中检查扩展名生成标题一样，您必须检查创建$ img2

的方式

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']);
}

我想为您的信息添加的另一件事是检查图像mime类型而不是检查扩展名。为此你可以使用getimagesize函数，它返回一个数组，你可以通过$ retun_array ['mime']检查mime类型。

如果没有正确创建或存储，PNG图像通常会产生问题。损坏的图像也可能导致此问题。希望这对你有用。

Answer 2

我留下了我的缩略图代码，并将它们保存到目标文件夹

    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 );
    }
}