1. An image processing apparatus which emphasizes an image data, said apparatus comprising: a smoothing unit configured to smooth the image data by using a filter; a difference generation unit configured to calculate a difference between the image data and smoothed image data obtained by said smoothing unit; a multiplying unit configured to generate a product to multiply said difference generated by said difference generation unit by an emphasis coefficient based on a value of said difference; and a combining unit configured to combine said image data and said product, wherein said multiplying unit multiplies a larger emphasis coefficient as a larger value of said difference.