Smooth round PNG with transparent background via PHP and GD

Question

I'm trying to use PHP with GD to create a round version of a classic photo (a square one), in PNG with a transparent background... I've succeeded to do it by following some tutorials on the internet (such as http://thedebuggers.com/transparent-circular-crop-using-php-gd/ ), but the circle is not smooth so the quality is not acceptable for my use...

I tried with the following way, but I'm facing a problem: only the top left corner is transparent (and the circle is, during PI/2, totally perfect), but 3/4 of the black background built with GD is still here (the bottom corners and the top right corner).

Could you please help me about this issue?

Thanks in advance,

    //$image_s is a resource (photo loaded to be processed)
    $width = imagesx($image_s);
    $height = imagesy($image_s);
    $newwidth = 500;
    $newheight = 500;
    $image = imagecreatetruecolor($newwidth, $newheight);
    imagealphablending($image, true);
    imagecopyresampled($image, $image_s, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);

    //create masking
    $mask = imagecreatetruecolor($newwidth, $newheight);
    $transparent = imagecolorallocate($mask, 255, 0, 0);
    imagecolortransparent($mask,$transparent);
    imagefilledellipse($mask, $newwidth/2, $newheight/2, $newwidth, $newheight, $transparent);
    $red = imagecolorallocate($mask, 0, 0, 0);
    imagecopymerge($image, $mask, 0, 0, 0, 0, $newwidth, $newheight, 100);
    imagecolortransparent($image,$red);
    imagefill($image, 0, 0, $red);

    $finalImage = imagecreatetruecolor(100, 100);
    $transparentColor = imagecolorallocatealpha($image, 0, 0, 0, 127);
    imagefill($image, 0, 0, $transparentColor);
    imagealphablending($finalImage, false);
    imagesavealpha( $finalImage, true );
    imagecopyresampled($finalImage, $image, 0, 0, 0, 0, 100, 100, $newwidth, $newheight);

    imagepng($finalImage, $markerPicturePath);
    imagedestroy($image);
    imagedestroy($mask);
    imagedestroy($finalImage);

    //$markerPicturePath is now a PNG picture with a round extracted from the photo, with a top left transparent corner and 3 other black corners...

Answer 1

It seems the background needs to be continuous from the top left corner to other corners to allow the transparency everywhere, so I added some space when I build the ellipse.

I edited the imagefilledellipse line to imagefilledellipse($mask, $tempWidth/2, $tempHeight/2, $tempWidth-2, $tempHeight-2, $transparent);

Thanks,