An image processing circuit for processing at least one jagged edge in an image represented by an input video signal. The image processing circuit includes: a detection module for detecting an edge by labeling a specific portion within input data carried by the input video signal to indicate whether the specific portion corresponds to a specific edge and further generates a detection result; a line buffer for temporarily storing input data carried by the input video signal; and a processing unit, coupled to the detection module and the line buffer, for processing the input data according to the detection result to output an output video signal.