PHP中的图像调整大小问题-gd创建难看的调整大小图像

Question

I am creating thumbnails of fixed height and width from my PHP script using the following function

/*creates thumbnail of required dimensions*/
function createThumbnailofSize($sourcefilepath,$destdir,$reqwidth,$reqheight,$aspectratio=false)
{
    /*
     * $sourcefilepath =  absolute source file path of jpeg
     * $destdir =  absolute path of destination directory of thumbnail ending with "/"
     */
    $thumbWidth = $reqwidth; /*pixels*/
    $filename = split("[/\\]",$sourcefilepath);
    $filename = $filename[count($filename)-1];
    $thumbnail_path = $destdir.$filename;
    $image_file = $sourcefilepath;

    $img = imagecreatefromjpeg($image_file);
    $width = imagesx( $img );
    $height = imagesy( $img );

    // calculate thumbnail size
    $new_width = $thumbWidth;
    if($aspectratio==true)
    {
        $new_height = floor( $height * ( $thumbWidth / $width ) );
    }
    else
    {
        $new_height = $reqheight;
    }

    // create a new temporary image
    $tmp_img = imagecreatetruecolor( $new_width, $new_height );

    // copy and resize old image into new image
    imagecopyresized( $tmp_img, $img, 0, 0, 0, 0, $new_width, $new_height, $width, $height );

    // save thumbnail into a file

    $returnvalue = imagejpeg($tmp_img,$thumbnail_path);
    imagedestroy($img);
    return $returnvalue;
}

and I call this function with following parameters

createThumbnailofSize($sourcefilepath,$destdir,48,48,false);

but the problem is the resulting image is of very poor quality, when I perform the same operation with Adobe Photo shop, it performs a good conversion.. why it is so? I am unable to find any quality parameter, through which I change the quality of output image..

Answer 1

使用imagecopyresampled()代替imagecopyresized() 。

Answer 2

if it is image quality you are after you need to give the quality parameter when you save the image using imagejpeg($tmp_img,$thumbnail_path,100) //default value is 75

/*creates thumbnail of required dimensions*/
function 
createThumbnailofSize($sourcefilepath,$destdir,$reqwidth,$reqheight,$aspectratio=false)
{
    /*
     * $sourcefilepath =  absolute source file path of jpeg
     * $destdir =  absolute path of destination directory of thumbnail ending with "/"
     */
    $thumbWidth = $reqwidth; /*pixels*/
    $filename = split("[/\\]",$sourcefilepath);
    $filename = $filename[count($filename)-1];
    $thumbnail_path = $destdir.$filename;
    $image_file = $sourcefilepath;

$img = imagecreatefromjpeg($image_file);
$width = imagesx( $img );
$height = imagesy( $img );

// calculate thumbnail size
$new_width = $thumbWidth;
if($aspectratio==true)
{
    $new_height = floor( $height * ( $thumbWidth / $width ) );
}
else
{
    $new_height = $reqheight;
}

// create a new temporary image
$tmp_img = imagecreatetruecolor( $new_width, $new_height );

// copy and resize old image into new image
imagecopyresized( $tmp_img, $img, 0, 0, 0, 0, $new_width, $new_height, $width, $height );

// save thumbnail into a file

$returnvalue = imagejpeg($tmp_img,$thumbnail_path,100);
imagedestroy($img);
return $returnvalue;

}

Answer 3

You could also consider using ImageMagick ( http://us3.php.net/manual/en/book.imagick.php ) instead of Gd. I had the same problem just a couple of days ago with Java. Going for ImageMagick instead of Java Advanced Images resultet in a huge quality difference.

Answer 4

You might also want to take a look at the Image_Transform PEAR package . It takes care of a lot of the low-level details for you and makes creating and maniuplating images painless. It also lets you use either GD or ImageMagick libraries. I've used it with great success on several projects.

Answer 5

tried using the php.Thumbnailer ?

$thumb=new Thumbnailer("photo.jpg");
$thumb->thumbSquare(48)->save("thumb.jpg");

Result photo will be 48x48px. Easy right? :)