php图像调整大小功能不保留图像质量

Question

我正致力于调整图像大小。上传后，它会通过一个脚本来制作副本，但调整后的副本会以较差的质量返回。我想知道是否有人可以看看我哪里出错了。图像的大小正确，但看起来像素化了。

php表单：

    <form enctype="multipart/form-data" method="post" action="image_upload_script.php">
Choose your file here:
<input name="uploaded_file" type="file"/><br /><br />
<input type="submit" value="Upload It"/>
</form>

image_upload_script：

   <?php
// Access the $_FILES global variable for this specific file being uploaded
// and create local PHP variables from the $_FILES array of information
$fileName = $_FILES["uploaded_file"]["name"]; // The file name
$fileTmpLoc = $_FILES["uploaded_file"]["tmp_name"]; // File in the PHP tmp folder
$fileType = $_FILES["uploaded_file"]["type"]; // The type of file it is
$fileSize = $_FILES["uploaded_file"]["size"]; // File size in bytes
$fileErrorMsg = $_FILES["uploaded_file"]["error"]; // 0 for false... and 1 for true
$kaboom = explode(".", $fileName); // Split file name into an array using the dot
$fileExt = end($kaboom); // Now target the last array element to get the file extension
// START PHP Image Upload Error Handling --------------------------------------------------
if (!$fileTmpLoc) { // if file not chosen
    echo "ERROR: Please browse for a file before clicking the upload button.";
    exit();
} else if($fileSize > 5242880) { // if file size is larger than 5 Megabytes
    echo "ERROR: Your file was larger than 5 Megabytes in size.";
    unlink($fileTmpLoc); // Remove the uploaded file from the PHP temp folder
    exit();
} else if (!preg_match("/.(gif|jpg|png)$/i", $fileName) ) {
     // This condition is only if you wish to allow uploading of specific file types    
     echo "ERROR: Your image was not .gif, .jpg, or .png.";
     unlink($fileTmpLoc); // Remove the uploaded file from the PHP temp folder
     exit();
} else if ($fileErrorMsg == 1) { // if file upload error key is equal to 1
    echo "ERROR: An error occured while processing the file. Try again.";
    exit();
}
// END PHP Image Upload Error Handling ----------------------------------------------------
// Place it into your "uploads" folder mow using the move_uploaded_file() function
$moveResult = move_uploaded_file($fileTmpLoc, "uploads/$fileName");
// Check to make sure the move result is true before continuing
if ($moveResult != true) {
    echo "ERROR: File not uploaded. Try again.";
    unlink($fileTmpLoc); // Remove the uploaded file from the PHP temp folder
    exit();
}
unlink($fileTmpLoc); // Remove the uploaded file from the PHP temp folder
// ---------- Include Universal Image Resizing Function --------
include_once("resize.php");
$target_file = "uploads/$fileName";
$resized_file = "uploads/resized_$fileName";
$wmax = 84;
$hmax = 78;
resize($target_file, $resized_file, $wmax, $hmax, $fileExt);
// ----------- End Universal Image Resizing Function -----------
// Display things to the page so you can see what is happening for testing purposes
echo "The file named <strong>$fileName</strong> uploaded successfuly.<br /><br />";
echo "It is <strong>$fileSize</strong> bytes in size.<br /><br />";
echo "It is an <strong>$fileType</strong> type of file.<br /><br />";
echo "The file extension is <strong>$fileExt</strong><br /><br />";
echo "The Error Message output for this upload is: $fileErrorMsg";
?>

resize.php：

    <?php
// Function for resizing jpg, gif, or png image files
function resize($target, $newcopy, $w, $h, $ext) {
    list($w_orig, $h_orig) = getimagesize($target);
    $scale_ratio = $w_orig / $h_orig;
    if (($w / $h) > $scale_ratio) {
           $w = $h * $scale_ratio;
    } else {
           $h = $w / $scale_ratio;
    }
    $img = "";
    $ext = strtolower($ext);
    if ($ext == "gif"){ 
      $img = imagecreatefromgif($target);
    } else if($ext =="png"){ 
      $img = imagecreatefrompng($target);
    } else { 
      $img = imagecreatefromjpeg($target);
    }
    $tci = imagecreatetruecolor($w, $h);
    // imagecopyresampled(dst_img, src_img, dst_x, dst_y, src_x, src_y, dst_w, dst_h, src_w, src_h)
    imagecopyresampled($tci, $img, 0, 0, 0, 0, $w, $h, $w_orig, $h_orig);
    imagejpeg($tci, $newcopy, 80);
}
?>

欢迎所有反馈，谢谢。