使用codeigniter上传和调整图像大小

Question

以下是codeigniter中upload和resize的代码。 upload一切正常，但resize一直给我错误：

  

您的服务器不支持GD功能来处理此图像类型。

function do_upload()
{
    $config['upload_path'] = './gallery/gallery_big/';
    $config['allowed_types'] = 'jpg|jpeg|png|gif';
    $config['max_size'] = '900000 * 50';
    $config['max_width']  = '21024 * 50';
    $config['max_height']  = '21068 * 50';
    $config['remove_spaces']= TRUE;
    $config['upload_url']=site_url()."gallery/gallery_big/";

    $this->load->library('upload', $config);
    $this->upload->initialize($config);
    $field_name ="upfiles";
    $upload_data = $this->upload->data(); 
    $file_name =   $upload_data['file_name'];

    if(!$this->upload->do_upload($field_name))
    {
        $error = $this->upload->display_errors();

        ?>
            <script type="text/javascript">
                alert("<?php echo $error; ?>");
            </script>
        <?php
    }
    else
    {
        $success ='File Successfully Uploaded !!';

        ?>
            <script type="text/javascript">   
                alert("<?php echo $success; ?>");
            </script>
        <?php
    }

    $this->resize_img();
    //$this->resize_img1();
    //$this->resize_img2();
} 

function resize_img()
{
    $config1['image_library'] = 'gd2';
    $config1['source_image']='./gallery/gallery_big/';
    $config1['maintain_ratio'] = TRUE;
    $config1['quality'] = 100;
    $config1['new_image']='./gallery/thumbnails/';
    $config1['width']= 100;
    $config1['height']= 100;      

    $this->image_lib->initialize($config1);
    if(!$this->image_lib->resize())
    {        
        $error = $this->image_lib->display_errors();

        ?>  
            <script type="text/javascript">
                alert("<?php echo $error; ?>");
            </script>
        <?php
    }

    //$this->image_lib->clear();
}