1. A medical image display apparatus that displays, on a display screen, a display image having undergone gray level transform of changing a number of gray levels of a medical image, the medical image display apparatus comprising: at least one processor and at least one memory that cooperate to act as units comprising: (a) an obtaining unit configured to obtain, in the medical image, a representative value of pixel values concerning a region of a block, wherein (1) the block corresponds to a partial region in a region designated in the display image and (2) each partial region in the designated region corresponds to a respective block; (b) a setting unit configured to set a specific region in the display screen so as to include the designated region; and (c) a display control unit configured to (i) superimpose and display and (ii) arrange representative values obtained by the obtaining unit on the specific region in correspondence with an arrangement of the partial regions.