After trying and trying, it is the solution: imagecopymerge() Explain me someone, why?

<?php

$image  =  http://content.wuala.com/contents/mike.walker/sharing/10891.png?dl=1 ;

// ---------------------------------------- Prepare

$scale = 1;

// Get meta for image
$info = getimagesize($image);
$info = array(
     width   => $info[ 0 ],
     height  => $info[ 1 ],
     bits    => $info[  bits  ],
     mime    => $info[  mime  ]
);

// Get res for image
$image = imagecreatefrompng($image);

$width  = $info[  width  ] * $scale;
$height = $info[  height  ] * $scale;

$new_width  = (int)($info[  width  ] * $scale);
$new_height = (int)($info[  height  ] * $scale);
$xpos       = (int)(($width - $new_width) / 2);
$ypos       = (int)(($height - $new_height) / 2);

$image_old = $image;
$image     = imagecreatetruecolor($width, $height);
$image2     = imagecreatetruecolor($width, $height);

//imagetruecolortopalette($image, FALSE, 255);
imagealphablending($image, true);
imagesavealpha($image, true);
$background = imagecolorallocatealpha($image, 255, 255, 255, 0);
//$background = imagecolortransparent($image, imagecolorexact($image, 254, 0, 254));
//$background = imagecolorallocate($image, 254, 0, 3);
imagecolortransparent($image2, $background);

imagefilledrectangle($image, 0, 0, $width, $height, $background);
//imagefilledrectangle($image2, 0, 0, $width, $height, $background);
imagecopymerge($image, $image_old, 0, 0, 0, 0, $new_width, $new_height, 100);
imagecopyresampled($image2, $image, $xpos, $ypos, 0, 0, $new_width, $new_height, $info[  width  ], $info[  height  ]);
//imagecopyresampled($image2, $image_old, $xpos, $ypos, 0, 0, $new_width, $new_height, $info[  width  ], $info[  height  ]);

// ------------------------------------------------ Convert

$scale = .9;

$width  = $info[  width  ] * $scale;
$height = $info[  height  ] * $scale;

$new_width  = (int)($info[  width  ] * $scale);
$new_height = (int)($info[  height  ] * $scale);
$xpos       = (int)(($width - $new_width) / 2);
$ypos       = (int)(($height - $new_height) / 2);

$image_old = $image2;
$image     = imagecreatetruecolor($width, $height);

//imagetruecolortopalette($image, FALSE, 255);
imagealphablending($image, true);
imagesavealpha($image, true);
$background = imagecolorallocatealpha($image, 255, 0, 255, 0);
//$background = imagecolortransparent($image, imagecolorexact($image, 254, 0, 254));
//$background = imagecolorallocate($image, 254, 0, 3);
imagecolortransparent($image2, $background);

//imagefilledrectangle($image2, 0, 0, $width, $height, $background);
//imagefilledrectangle($image2, 0, 0, $width, $height, $background);
//imagecopymerge($image, $image_old, 0, 0, 0, 0, $new_width, $new_height, 100);
//imagecopyresampled($image2, $image, $xpos, $ypos, 0, 0, $new_width, $new_height, $info[  width  ], $info[  height  ]);
imagecopyresampled($image, $image_old, $xpos, $ypos, 0, 0, $new_width, $new_height, $info[  width  ], $info[  height  ]);

header( Content-type: image/png );
imagepng($image);
//imagepng($image2, __DIR__ .  /resized.png );