function of add logo to image
public function overlay()
{
$this->load->library('image_lib');
$config['image_library'] = 'gd2';
$config['source_image'] = 'uploads/5a6b7412ec441hh2.jpg';
$config['wm_type'] = 'overlay';
$config['wm_overlay_path'] = 'assets/img/logo-blanc.png';
$config['new_image'] = 'uploads//output.jpg';
//the overlay image
$config['wm_opacity'] =70; # 1 not transparent - 100 fully transparent
# coordinates of the pixel color on the overlay to make transparent
$config['wm_x_transp'] =100;
$config['wm_y_transp'] = 100;
$config['wm_vrt_alignment'] = 'middle';
$config['wm_hor_alignment'] = 'center';
$config['wm_padding'] = '20';
$this->image_lib->initialize($config);
if (!$this->image_lib->watermark()) {
echo $this->image_lib->display_errors();
} else {
echo 'Successfully updated image with watermark';
}
}