PURPOSE:To generate a binary picture provided with feature of sketch fashion by sampling a main contour line and shading information from a natural picture, and generating a sketch-fashion picture from sampled contour line and shading information. CONSTITUTION:A contour line sampling means 4 performs the quantitative determination of local gradients in four adjacent directions from an inputted multilevel original picture 217, and generates a contour line picture 213 set as a value which means the contour line when a quantitative determination value exceeds a first threshold value, and a value which means a background in the case other than that. A shading sampling means 102 generates a shading picture 215 depending on shading expression set as a value in which a part where the pixel value of the original picture is smaller than a second threshold value means shade, and a value which means the background in the case other than that. A picture synthesizing means 103 inputs the contour line picture 213 and the shading picture 215, and outputs by generating the sketch-fashion picture 218 set as a value which means the value of the background when both picture element values of those pictures at the same coordinate position means the background, and a value which means a diagram in the case other than that.
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