An electronic device may include a display and an optical sensor formed underneath the display. The electronic device may include a plurality of transparent windows that overlap the optical sensor. The resolution of the display panel may be reduced in some areas due to the presence of the transparent windows. To prevent a visible border between the reduced resolution areas of the display and full resolution areas of the display, uniformity compensation circuitry may be used to compensate pixel data. The uniformity compensation circuitry may output compensated pixel data for the display using one or more compensation maps that include compensation factors associated with pixel locations. The uniformity compensation circuitry may also use region-specific gamma look-up tables to apply different gamma curves to pixels in different regions of the display. The uniformity compensation circuitry may also be used to form a transition region between different regions of the display.