To display the images of excellent visibility for emphasizing the contrast of a target area.
For a photographed image, a density transformation function for transforming the entire gradation level is calculated from the gradation histogram (b) of a target interested area A201. For image data repeatedly inputted by a frame unit, the target interested area is decided before photographing and a transformation function is continuously calculated from the gradation histogram of repeatedly inputted respective picture elements inside the interested area. The transformation function is the linear transformation of the histogram inside the interested area, and turned to simply the constant multiple of an original picture element value for a picture element gradation other than the target interested area. Thus, the linear transformation is performed so as to attain histogram distribution like the figure (c) and the contrast of the area under consideration is optimally improved.
SATO NORIO
NAKANISHI KUNIO
SHIBUKAWA SHIGERU
YODA HARUO
