startActivityForResult(new Intent(Intent.ACTION_PICK,android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI),54);

private byte[] GetFileBytes(Uri uri)
{
    ByteArrayOutputStream bos = new ByteArrayOutputStream(200000);
    InputStream imageStream;
    try {
        imageStream = getContentResolver().openInputStream(uri);
        byte[] buffer;
        buffer = new byte[100000];
        while ((imageStream.read(buffer)) != -1) {
            bos.write(buffer);
        }
    } catch (Throwable e) {
        e.printStackTrace();
    }
    return bos.toByteArray();
}

private MultipartEntity getEntity(byte[] bytes)
{
    MultipartEntity entity = new MultipartEntity();
    InputStream in = new ByteArrayInputStream(bytes);
    ContentBody bin = new InputStreamBody(in, "Image_" + c.getTimeInMillis() + ".jpg");
    entity.addPart("image_query_string_variable_name", bin);
}

private void PostData(MultipartEntity entity)
{
    HttpParams httpParameters = new BasicHttpParams();
    HttpConnectionParams.setConnectionTimeout(httpParameters, 20000);
    HttpConnectionParams.setSoTimeout(httpParameters, 20000);
    DefaultHttpClient client = new DefaultHttpClient(httpParameters);

    HttpPost request = new HttpPost("http://www.you_server_url.com/someFileName.php");
    request.setEntity(entity);

    HttpResponse response = null;
    response = client.execute(request);
    BufferedReader rd = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
    StringBuffer result = new StringBuffer();
    String line = "";
    while ((line = rd.readLine()) != null) {
        result.append(line);
    }
    //
    // Process the returned result from server...
    //
}