imagecopyresampled png包含正方形图像

Question

I have a landscape PNG image which I want to convert to a square image but with the whole image visable (in css-terms: contain).

I have managed that, and the transparency behind the image is preserved, but above and below the image it is black. How do I manage to get that transparent too?

                move_uploaded_file($uploadedFile,$targetFile);
                $image = ($fileExtension == 'png') ? imagecreatefrompng($targetFile) : imagecreatefromjpeg($targetFile);
                unlink($targetFile);
                $filename = $targetFile;        
                $width = imagesx($image);
                $height = imagesy($image);
                $thumb_width = 400;
                $thumb_height = 400;

                $thumb = imagecreatetruecolor( $thumb_width, $thumb_height );
                $dst_image = $thumb;
                $src_image = $image;
                $dst_w = $thumb_width;
                $dst_h = $thumb_height;
                $y = $width > $height ? ($width-$height)/2 : 0;
                $x = $width > $height ? 0 : ($height-$width)/2;
                $size = $width > $height ? $width : $height;
                $src_w = $size;
                $src_h = $size;
                $src_x = -$x;
                $src_y = -$y;

                imagealphablending($thumb, false);
                imagesavealpha($thumb, true);  
                imagealphablending($image, false);
                imagesavealpha($image, true);           

                imagecopyresampled($dst_image,$src_image,$dst_x,$dst_y,$src_x,$src_y,$dst_w,$dst_h,$src_w,$src_h);
                $blobName = 'icon.png';
                putBlobImage($storageClient,$storageContainer,$thumb,$blobName,$fileExtension);

---

UPDATE

I did manage to remove the black boxes, but now also the black from my image disappeared (most of it though). How do I preserve the black from the original picture? See example and code below.

                    move_uploaded_file($uploadedFile,$targetFile);
                $image = ($fileExtension == 'png') ? imagecreatefrompng($targetFile) : imagecreatefromjpeg($targetFile);
                unlink($targetFile);
                $filename = $targetFile;        
                $width = imagesx($image);
                $height = imagesy($image);
                $thumb_width = 400;
                $thumb_height = 400;

                $thumb = imagecreatetruecolor( $thumb_width, $thumb_height );

                $black = imagecolorallocate($thumb, 0, 0, 0);
                imagecolortransparent($thumb,$black);

                $dst_image = $thumb;
                $src_image = $image;
                $sc = $width/$thumb_width;
                $dst_w = $width/$sc;
                $dst_h = $height/$sc;
                $y = $width > $height ? (400-$dst_h)/2 : 0;
                $x = $width > $height ? 0 : (400-$dst_w)/2;
                $size = $width > $height ? $width : $height;
                $src_w = $width;
                $src_h = $height;
                $position = array(0,0,$x,$y);
                list($src_x,$src_y,$dst_x,$dst_y) = $position;


                //imagealphablending($src_image, false);
                //imagesavealpha($src_image, true);  
                //imagealphablending($dst_image, true);
                //imagesavealpha($dst_image, true);             


                imagecopyresampled($dst_image,$src_image,$dst_x,$dst_y,$src_x,$src_y,$dst_w,$dst_h,$src_w,$src_h);
                $blobName = 'icon.png';
                putBlobImage($storageClient,$storageContainer,$thumb,$blobName,$fileExtension);
                $data = $blobName.'@@'.$uploadedFileName.'@@'.$fileExtension;
                $return .= $data;

Answer 1

I finally managed to fix it!

move_uploaded_file($uploadedFile,$targetFile);
$image = ($fileExtension == 'png') ? imagecreatefrompng($targetFile) : imagecreatefromjpeg($targetFile);
unlink($targetFile);
$filename = $targetFile;        
$width = imagesx($image);
$height = imagesy($image);
$thumb_width = 400;
$thumb_height = 400;
$thumb = imagecreatetruecolor( $thumb_width, $thumb_height );

$color = imagecolorallocatealpha($thumb, 255, 0, 0, 127);
imagefill($thumb, 0, 0, $color);
// THE LINE ABOVE DID THE TRICK


imagecolortransparent($thumb,$color);

$dst_image = $thumb;
$src_image = $image;
$sc = $width/$thumb_width;
$dst_w = $width/$sc;
$dst_h = $height/$sc;
$y = $width > $height ? (400-$dst_h)/2 : 0;
$x = $width > $height ? 0 : (400-$dst_w)/2;
$size = $width > $height ? $width : $height;
$src_w = $width;
$src_h = $height;
$position = array(0,0,$x,$y);
list($src_x,$src_y,$dst_x,$dst_y) = $position;


//imagealphablending($src_image, false);
//imagesavealpha($src_image, true);  
//imagealphablending($dst_image, false);
//imagesavealpha($dst_image, true);


imagecopyresampled($dst_image,$src_image,$dst_x,$dst_y,$src_x,$src_y,$dst_w,$dst_h,$src_w,$src_h);
$blobName = 'icon.png';
putBlobImage($storageClient,$storageContainer,$thumb,$blobName,$fileExtension);