1. An image processing apparatus comprising a controller configured to perform: acquiring target image data representative of a target image, the target image data including a plurality of pixel values for a plurality of pixels in the target image data; determining whether or not a ratio of a number of first type pixels relative to a number of the plurality of pixels in the target image data is greater than or equal to a prescribed value, the first type pixels being the pixels in the target image data whose pixel values are within a first range, the first range being defined based on a color value indicative of a background color of the target image; executing a first correction on the target image data when the ratio is determined to be greater than or equal to the prescribed value, the first correction correcting, among pixel values in the target image data, both of internal pixel values which are within a second range and external pixel values which are out of the second range, the second range containing the color value of the background color; executing a second correction on the target image data when the ratio is determined to be smaller than the prescribed value, the second correction correcting the internal pixel values and not correcting the external pixel values; and outputting corrected target image data that is obtained by executing the first correction or the second correction on the target image data.