Image processing method, image processing apparatus, noise removing method, and noise removing apparatus

An image processing method for extracting a uniform region whose luminance level change is small from an image containing noise, comprising the steps of:

• extracting a high frequency component of a luminance signal of said image over an entire portion of said image within one screen;
• generating a histogram of a luminance level of said luminance signal for one screen on the basis of the extracted output value;
• analyzing said histogram to calculate a predetermined coefficient indicative of likeness of the uniform region every said luminance level;
• and
• establishing a correspondence relationship between said predetermined coefficient and all of the pixel positions on the image in correspondence to the luminance level of said luminance signal from each of said pixel positions.

A noise removing apparatus for removing noise of an image, comprising:

• extracting means for extracting a high frequency component of a luminance signal of said image over an entire portion of said image within one screen;
• histogram generating means for generating a histogram of a luminance level of said luminance signal for one screen on the basis of the output value of said extracting means;
• coefficient calculating means for analyzing said histogram to calculate a predetermined coefficient indicative of likeness of the uniform region every said luminance level;
• pixel-position-depending coefficient producing means for establishing a correspondence relationship between said predetermined coefficient calculated by said coefficient calculating means and all of the pixel positions on the image in correspondence to the luminance level of said luminance signal from each of said pixel position;
• and
• smoothing means for smoothing said luminance signals of all of said pixel positions on said image on the basis of said preselected coefficients made in correspondence with all of said pixel positions on said image.

A noise removing method for removing noise of an image, comprising the steps of:

• extracting a high frequency component of a luminance signal of said image over an entire portion of said image within one screen;
• generating a histogram of a luminance level of said luminance signal for one screen on the basis of the extracted value;
• analyzing said histogram to calculate a predetermined coefficient indicative of likeness of the uniform region every said luminance level;
• establishing a correspondence relationship between said predetermined coefficient and all of the pixel positions on the image in response to the luminance level of said luminance signal from each of said pixel positions;
• and
• smoothing said luminance signals of all of the pixel positions within one screen on the basis of said preselected coefficients made in correspondence to all of said pixel positions on the screen.