The present invention provides an image processing circuit for compensating image data for a display panel used for displaying first and second image patterns respectively having first and second current loadings. The image processing circuit is used for: receiving a first original image data of the first image pattern and a second original image data of the second image pattern having the same brightness value for a pixel at the same location; converting the first original image data into a first final image data to compensate for an IR drop according to the first current loading; and converting the second original image data into a second final image data to compensate for the IR drop according to the second current loading. The first final image data and the second final image data have substantially the same brightness value for the pixel at the same location.