Methods and systems for detecting an object borderline. A first image with respect to the object can be captured by an image-capturing unit without a flash light and borderlines of the object can be detected. If the detection is successful, the detected borderlines can be outputted. Otherwise, a second image with respect to the object can be captured by the image-capturing unit by applying a flash light and the borderlines can be detected in the image. A geometric transformation between the two images can then be estimated. Finally, the border lines in the first image can be determined by transforming the borderlines detected in the second image. Such an approach effectively detects the appliance borderlines and avoids artifacts caused by applying flash.