registerImportOperation example

YourPlugin.php

// Register special hook for Markdown processing
function registerImportOperation(&$data, $handle) {
	    
    // Get field info
    $field = craft()->fields->getFieldByHandle($handle);
    
    // If it's a field ofcourse
    if(!is_null($field)) {
        
        // For some fieldtypes the're special rules
        switch($field->type) {
        
            case ImportModel::FieldTypeRichText:
            
                // Replace br's with newlines
                $data = str_replace(' <br> ', '<br>', $data);
                $data = str_replace('<br>', "\r\n", $data);
                
                // Fix links
                $data = str_replace('] (http://', '](http://', $data);
                
                // Parse markdown
                $data = StringHelper::parseMarkdown($data);
            
            break;
            
        }
        
    }
    
    return $data;
    	
}