A determination image generator of an image processing apparatus compares, in pixel units, sixth image data with seventh image data or second image data. The sixth image data is obtained by selecting, in pixel units, a minimum value of a value of first image data and a value of fifth image data which is edge enhanced data of the first image data. The seventh image data is obtained by performing first processing to second image data. The generator sets in the determination image a third value for pixels where a value of the sixth image data is equal to or less than a value of the seventh image data or the second image data, or is equal to or less than a sum of the value of the seventh image data or the second image data and a first value, and sets a different value for all other pixels.