A portable electronic device with camera function and an image capture method with auto exposure control. The disclosed method comprises the following steps: obtaining a pre-view frame from a camera module; dividing the pre-view frame into a plurality of blocks and calculating representative brightness values of the blocks; assigning weight values to the blocks according to the representative brightness values; obtaining a weighted brightness value by performing a weighted operation on the representative brightness values based on the weight values of the blocks; setting an auto exposure parameter of the camera module based on the weighted brightness value; and controlling the camera module for capturing images based on the auto exposure parameter.