Resize image according to width only & crop Extra Height , Codeigniter

I need to resize my images according to width only , not height :( since i am using ** $config['maintain_ratio'] = TRUE;** , codeigniter solves it automatically (thats the problem) sometimes i get a black solid as an extra width or height ,

i have looked at all of the questions relating to codegniter's image library and i couldn't find anything related to my problem :(

Here is a description on the final result...

After uploading am having this ...

$this->load->library('md_image');
        $source='assets/img/hotellist/'.$data1['hotel_pictures'];
        $width=746;
        $height=400;
        $dest = FALSE;
        //$this->md_image->resize_image($source, $width, $height, $source);
            $config['image_library'] = 'gd2';//imagemagik
            $config['source_image'] = 'assets/img/hotellist/'.$data1['hotel_pictures'];
            //$config['image_library'] = 'imagemagick';
            //$config['library_path'] = '/usr/X11R6/bin/';
            $config['create_thumb'] = FALSE;
            $config['maintain_ratio'] = TRUE;
            $config['width']     = 746;
            $config['height']   = 400;
            $config['quality']   = 75;
            $config['encrypt_name'] = TRUE;
            $config['remove_spaces'] = TRUE;
            //$config['x_axis'] = 100;
            //$config['y_axis'] = 300;
            $img =$config['source_image'];
            //var_dump('check problem',$config['source_image']);

            $this->load->library('image_lib', $config);

            $this->image_lib->resize();

Then i am take caring of the cropping part

$new_img =$this->md_image->crop_to_ratio($source, $width, $height, $x = 17, $y = 9, $dest = FALSE);

to sum up , Someone uploads an image , it gets resized to according to width only and then it gets cropped

PS: incase someone needed it md_image

$this->load->library('md_image');
        $source='assets/img/hotellist/'.$data1['hotel_pictures'];
        $width=746;
        $height=400;
        $size = getimagesize($source);
        $resize_height=($size[1]*746)/$size[0];
        $dest = FALSE;
        //$this->md_image->resize_image($source, $width, $height, $source);
            $config['image_library'] = 'gd2';//imagemagik
            $config['source_image'] = 'assets/img/hotellist/'.$data1['hotel_pictures'];
            //$config['image_library'] = 'imagemagick';
            //$config['library_path'] = '/usr/X11R6/bin/';
            $config['create_thumb'] = FALSE;
            $config['maintain_ratio'] = TRUE;
            $config['width']     = 746;
            $config['height']   = $resize_height;
            $config['quality']   = 75;
            $config['encrypt_name'] = TRUE;
            $config['remove_spaces'] = TRUE;
            //$config['x_axis'] = 100;
            //$config['y_axis'] = 300;
            $img =$config['source_image'];
            //var_dump('check problem',$config['source_image']);

            $this->load->library('image_lib', $config);

            $this->image_lib->resize();