How to post an image file to the rails server

Hi guys, I am trying to post an image file to my rails backend server. But unfortunately I could not save the file to my server. Here is my code.

btnUploadFile.addEventListener("click", function(e){        
        var postData={
            "send_message":{
                "id":pickerValue,
                "message": textArea1.value,
                 "photo": uploadImgView.image,
                "user_id": user_id
            }
        };      
        var url = APPLICATION_URL+"/url.json?auth_token="+auth_token;       
        var ajaxCall = Ti.Network.createHTTPClient({
            onload: function(e) {
                Ti.API.info(this.responseText);
            },
            onerror: function(e) {
                // this function is called when an error occurs, including a timeout                
                Ti.API.info(e.error);
                Ti.API.info(this.responseText);
            }
        });
 
        ajaxCall.setRequestHeader("Content-Type", "application/json");
        //ajaxCall.setRequestHeader("Content-Type", "multipart/form-data");             
        ajaxCall.setRequestHeader('Accept','application/json');
        ajaxCall.setRequestHeader('charset','utf-8');
        ajaxCall.open("POST", url);
        ajaxCall.send(JSON.stringify(postData));        
    });

Processing by FeedbackController#create as JSON
  Parameters: {"{\"send_message\":{\"id\":\"3\",\"message\":\"Test image upload. \",\"photo\":{\"file\":{\"hidden\":false,\"nativePath\":\"content://media/extern
al/images/media/1921\",\"writable\":false,\"executable\":false,\"parent\":null,\"readonly\":true,\"directoryListing\":null,\"size\":0,\"apiName\":\"Ti.Proxy\",\"name\
":\"tia-1595633997.jpg\",\"symbolicLink\":false,\"bubbleParent\":true},\"nativePath\":\"file:///storage/emulated/0/Pictures/image/tia-1595633997.jpg\",\
"height\":2592,\"length\":574092,\"width\":1456,\"mimeType\":\"image/jpeg\",\"apiName\":\"Ti.Blob\",\"text\":null,\"type\":1,\"bubbleParent\":true},\"user_id\":13}}"=
>nil, "auth_token"=>"VnFQWwQPkiPqMXHzjCLi"}

But when I try to save the image files along with the message from the text area. Null values for the image is getting saved in the table.

Thanks,

Varun Krishna. P