Image processing apparatus and method for allowing the dynamic range of digital image data having a wide dynamic range to be compressed while preserving information of the digital image data

An image processing apparatus comprising:

• low-pass filtering means for removing a high frequency component of an image signal applied;
• a high frequency component extracting circuit for extracting the high frequency component of said image signal applied;
• dividing means for dividing the image signal whose high frequency component is removed by said low pass filtering means into a high luminance image signal and a low luminance image signal using a predetermined threshold value;
• luminance level conversion processing means for separately subjecting said high luminance image signal and said low luminance image signal obtained by the division by said dividing means to luminance level conversion processing so that the lowest luminance level of said high luminance image signal is less than or equal to the highest luminance level of said low luminance image signal;
• and
• image signal generating means for synthesizing said high luminance image signal and said low luminance image signal subjected to the luminance level conversion processing by said luminance level conversion processing means as well as said high frequency component extracted by said high frequency component extracting circuit to generate an image signal corresponding to one frame image.

An image processing apparatus comprising:

• dividing means for dividing digital luminance image data applied into high luminance image data and low luminance image data using a predetermined threshold value;
• luminance level conversion processing means for separately subjecting said high luminance image data and said low luminance image data obtained by the division by said dividing means to luminance level conversion processing such that the lowest luminance level of said high luminance image data is less than or equal to the highest luminance level of said low luminance image data;
• and
• digital luminance image data generating means for synthesizing said high luminance image data and said low luminance image data subjected to the luminance level conversion processing by said luminance level conversion processing means to generate digital luminance image data corresponding to one frame image.

An image processing method comprising the steps of:

• removing a high frequency component of digital luminance image data applied;
• subtracting from said digital luminance image data applied to digital luminance image data whose high frequency component is removed, to generate a signal representing the high frequency component;
• dividing the digital luminance image data whose high frequency component is removed into high luminance image data and low luminance image data using a predetermined threshold value;
• separately subjecting said high luminance image data and said low luminance image data obtained by the division to luminance level conversion processing so that the lowest luminance level of said high luminance image data is less than or equal to the highest luminance level of said low luminance image data;
• synthesizing said high luminance image data and said low luminance image data subjected to the luminance level conversion processing as well as said high frequency component extracted, to generate digital luminance image data corresponding to one frame image;
• and
• generating digital still picture image data from the digital luminance image data generated and digital chrominance component image data concerning a color applied.

An image processing method comprising the steps of:

• removing a high frequency component of an image signal applied;
• subtracting from said image signal applied the image signal whose high frequency component is removed, to generate a signal representing the high frequency component;
• dividing the image signal whose high frequency component is removed into a high luminance image signal and a low luminance image signal using a predetermined threshold value;
• separately subjecting said high luminance image signal and said low luminance image signal obtained by the division to luminance level conversion processing so that the lowest luminance level of said high luminance image signal is less than or equal to the highest luminance level of said low luminance image signal;
• and
• synthesizing said high luminance image signal and said low luminance image signal subjected to the luminance level conversion processing as well as said high frequency component generated, to generate an image signal corresponding to one frame image.

An image processing method comprising the steps of:

• dividing digital luminance image data applied into high luminance image data and low luminance image data using a predetermined threshold value;
• separately subjecting said high luminance image data and said low luminance image data obtained by the division to luminance level conversion processing such that the lowest luminance level of said high luminance image data is less than or equal to the highest luminance level of said low luminance image data;
• and
• synthesizing said high luminance image data and said low luminance image data subjected to the luminance level conversion processing, to generate digital luminance image data corresponding to one frame image.