function do_upload() {
		
		$config = array(
			'allowed_types' => 'jpg|jpeg|gif|png',
			'upload_path' => $this->gallery_path,
			'max_size' => 2000
		);
		
		$this->load->library('upload', $config);
		$this->upload->do_upload();
		$image_data = $this->upload->data();
		
		$config = array(
			'source_image' => $image_data['full_path'],
			'new_image' => $this->gallery_path . '/thumbs',
			'maintain_ration' => true,
			'width' => 180,
			'height' => 150
		);
		
		$this->load->library('image_lib', $config);
		$this->image_lib->resize();
		
	}

Upload and resize

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