I am using CodeIgniter to resize image, but the small image I have resized is low quality. Here is my code:
$config = array(
    'image_library' => 'gd2',
    'quality' => '100',
    'source_image' => $temp_full_path,
    'new_image' => $full_temp_path."img_mobile/",
    'maintain_ratio' => true,
    'create_thumb' => false,
    'width' => 50,
    'height' => 50
);              
$this->image_lib->initialize($config);              
$this->image_lib->resize();
How can make resize image with high quality like it's original image?
Here is original image, image resize generate from php code and image resize generate from codeigniter: Image
 
                        
Looking at the source code, GD2 doesn't use the "quality" parameter.
But some of the other libraries do use it.
Give ImageMagick a try.