1. An OSD apparatus for displaying an image using first and second video input signals and a blend coefficient value, the apparatus comprising: a region search device for generating an output signal, wherein the output signal is responsive to Human Visual System (HVS) characteristic elements and the first and second video input signals; an &agr; controller responsive to the blend coefficient value and the output signal from the region search device, wherein the &agr; controller outputs a controlled blend coefficient; a first combining unit for combining the controlled blend coefficient with the first video input signal; a subtractor for outputting a difference between a predetermined value and the controlled blend coefficient; a second combining unit for combining an output from the subtractor with the second video input signal; an adder for adding output values of the first combining unit and the second combining unit; and a rounding/limiting unit for controlling an output from the adder within a predetermined contrast range.