Image processing apparatus and image processing method

An image processing apparatus which corrects a gray scale by extending part of a luminance level range of an input video luminance signal to a dynamic range of a processing system, comprising:

• maximum value detecting means which detects a maximum value of the input video luminance signal;
• histogram detecting means which detects luminance distribution information of the input video luminance signal;
• maximum value correcting means which obtains a corrected maximum value by correcting the maximum value detected by the maximum value detecting means based on the luminance distribution information detected by the histogram detecting means;
• and
• luminance signal correcting means which extends the input video luminance signal so that the corrected maximum value obtained by the maximum value correcting means becomes a maximum value of the dynamic range of the processing system.

An image processing apparatus which corrects a gray scale by extending part of a luminance level range of an input video luminance signal to a dynamic range of a processing system, comprising:

• minimum value detecting means which detects a minimum value of the input video luminance signal;
• maximum value detecting means which detects a maximum value of the input video luminance signal;
• histogram detecting means which detects luminance distribution information of the input video luminance signal;
• minimum value correcting means which obtains a corrected minimum value by correcting the minimum value detected by the minimum value detecting means based on the luminance distribution information detected by the histogram detecting means;
• maximum value correcting means which obtains a corrected maximum value by correcting the maximum value detected by the maximum value detecting means based on the luminance distribution information detected by the histogram detecting means;
• and
• luminance signal correcting means which extends the input video luminance signal so that the corrected minimum value obtained by the minimum value correcting means and the corrected maximum value obtained by the maximum value correcting means respectively become a minimum value and a maximum value of the dynamic range of the processing system.

An image processing apparatus which corrects a gray scale of a displayed image by correcting an input video luminance signal, comprising:

• luminance signal correcting means which corrects the input video luminance signal and outputs a video luminance signal after correction;
• color-difference signal level detecting means supplied with a video color-difference signal corresponding to the input video luminance signal for detecting a level of the video color-difference signal;
• and
• correction degree limiting means which limits a degree of correction of the input video luminance signal in the luminance signal correcting means based on the level of the video color-difference signal detected by the color-difference signal level detecting means, and produces an output as an output video luminance signal.

An image processing method of correcting a gray scale by extending part of a luminance level range of an input video luminance signal to a dynamic range of a processing system, comprising:

• a minimum value detecting step of detecting a minimum value of the input video luminance signal;
• a histogram detecting step of detecting luminance distribution information of the input video luminance signal;
• a minimum value correcting step of obtaining a corrected minimum value by correcting the minimum value detected in the minimum value detecting step based on the luminance distribution information detected in the histogram detecting step;
• and
• a luminance signal correcting step of extending the input video luminance signal so that the corrected minimum value obtained in the minimum value correcting step becomes a minimum value of the dynamic range of the processing system.

An image processing method of correcting gray scale by extending part of a luminance level range of an input video luminance signal to a dynamic range of a processing system, comprising:

• a maximum value detecting step of detecting a maximum value of the input video luminance signal;
• a histogram detecting step of detecting luminance distribution information of the input video luminance signal;
• a maximum value correcting step of obtaining a corrected maximum value by correcting the maximum value detected in the maximum value detecting step based on the luminance distribution information detected in the histogram detecting step;
• and
• a luminance signal correcting step of extending the input video luminance signal so that the corrected maximum value obtained in the maximum value correcting step becomes a maximum value of the dynamic range of the processing system.

An image processing method of correcting a gray scale by extending part of a luminance level range of an input video luminance signal to a dynamic range of a processing system, comprising:

• a minimum value detecting step of detecting a minimum value of the input video luminance signal;
• a maximum value detecting step of detecting a maximum value of the input video luminance signal;
• a histogram detecting step of detecting luminance distribution information of the input video luminance signal;
• a minimum value correcting step of obtaining a corrected minimum value by correcting the minimum value detected in the minimum value detecting step based on the luminance distribution information detected in the histogram detecting step;
• a maximum value correcting step of obtaining a corrected maximum value by correcting the maximum value detected in the maximum value detecting step based on the luminance distribution information detected in the histogram detecting step;
• and
• a luminance signal correcting step of correcting the input video luminance signal so that the corrected minimum value obtained in the minimum value correcting step and the corrected maximum value obtained in the maximum value correcting step respectively become a minimum value and a maximum value of the dynamic range of the processing system.

An image processing method of correcting a gray scale by extending part of a luminance level range of an input video luminance signal to a dynamic range of a processing system, comprising:

• a video luminance signal correcting step of correcting the input video luminance signal and outputting a video luminance signal after correction;
• a color-difference signal level detecting step of detecting a level of video color-difference signal that is supplied corresponding to the input video luminance signal;
• and
• a correction degree limiting step of limiting a degree of correction of the input video luminance signal in the luminance signal correcting step based on the level of the video colordifference signal detected in the color-difference signal level detecting step, and producing an output as an output video luminance signal.

An image processing apparatus which detects a maximum luminance level of an original image in an input video luminance signal, comprising:

• first maximum value detecting means which detects in the input video luminance signal a maximum luminance level in a display area;
• histogram detecting means which detects an amount of distribution of the input video luminance signal at each luminance level in a luminance level range including the maximum luminance level detected by the first maximum value detecting means and a luminance level adjacent thereto;
• comparing means which determines, based on the amount of distribution detected by the histogram detecting means, whether the luminance level range includes information which is located at a luminance level away from the original image and is unrelated to the original image;
• replacing means which replaces, when the comparing means determines that the information unrelated to the original image is included, a luminance level with respect to the unrelated information in the input video luminance signal by a luminance level which unaffects detection of the maximum luminance level of the original image;
• and
• second maximum value detecting means which detects a maximum luminance level in an input video signal obtained after the luminance level with respect to the unrelated information is replaced by the replacing means.

An image processing apparatus which detects in an input video luminance signal a minimum luminance level of an original image, comprising:

• first minimum value detecting means which detects in the input video luminance signal a minimum luminance level in a display area;
• histogram detecting means which detects an amount of distribution of the input video luminance signal at each luminance level in a luminance level range including the minimum luminance level detected by the first minimum value detecting means and a luminance level adjacent thereto;
• comparing means which determines, based on the amount of distribution detected by the histogram detecting means, whether the luminance level range includes information which is located at a luminance level away from the original image and is unrelated to the original image;
• replacing means which replaces, when the comparing means determines that the information unrelated to the original image is included, a luminance level with respect to the unrelated information in the input video luminance signal by a luminance level which unaffects detection of the minimum luminance level of the original image;
• and
• second minimum value detecting means which detects a minimum luminance level in an input video signal obtained after the luminance level with respect to the unrelated information is replaced by the replacing means.

An image processing apparatus for obtaining a maximum value signal suitable for dynamic gray-scale correction in motion pictures, comprising:

• APL detecting means which detects an average luminance level in a display area of an input video luminance signal;
• APL varied value detecting means which detects a varied value at the average luminance level detected by the APL detecting means;
• maximum value detecting means which detects a maximum luminance level in the display area of the input video luminance signal;
• and
• filter means which controls the maximum luminance level detected by the maximum value detecting means in accordance with the varied value at the average luminance level detected by the APL varied value detecting means, and produces an output as the maximum value signal, wherein
• the filter means outputs the maximum luminance level as it is when the varied value is larger than a first predetermined value, fixedly outputs a maximum luminance level that is an immediately previous output when the varied value is smaller than a second predetermined value, and outputs the maximum luminance level that follows in accordance with the varied value when the varied value is larger than the second predetermined value and smaller than the first predetermined value.

An image processing apparatus for obtaining a minimum value signal suitable for dynamic gray-scale correction in motion pictures, comprising:

• APL detecting means which detects an average luminance level in a display area of an input video luminance signal;
• APL varied value detecting means which detects a varied value at the average luminance level detected by the APL detecting means;
• minimum value detecting means which detects a minimum luminance level in the display area of the input video luminance signal;
• and
• filter means which controls the minimum luminance level detected by the minimum value detecting means in accordance with the varied value at the average luminance level detected by the APL varied value detecting means, and produces an output as the minimum value signal, wherein
• the filter means outputs the minimum luminance level as it is when the varied value is larger than a first predetermined value, fixedly outputs a minimum luminance level that is an immediately previous output when the varied value is smaller than a second predetermined value, and outputs the minimum luminance level that follows in accordance with the varied value when the varied value is larger than the second predetermined value and smaller than the first predetermined value.

An image processing method of detecting a maximum luminance level of an original image in an input video luminance signal, comprising:

• a first maximum value detecting step of detecting in the input video luminance signal a maximum luminance level in a display area;
• a histogram detecting step of detecting an amount of distribution of the input video luminance signal at each luminance level in a luminance level range including the maximum luminance level detected in the first maximum value detecting step and a luminance level adjacent thereto;
• a comparing step of determining, based on the amount of distribution detected in the histogram detecting step, whether the luminance level range includes information which is located at a luminance level away from the original image and is unrelated to the original image;
• a replacing step of replacing, when it is determined in the comparing step that the information unrelated to the original image is included, a luminance level with respect to the unrelated information in the input video luminance signal by a luminance level which unaffects detection of the maximum luminance level of the original image;
• and
• a second maximum value detecting step of detecting a maximum luminance level in an input video signal obtained after the luminance level with respect to the unrelated information is replaced in the replacing step.

An image processing method of detecting a minimum luminance level of an original image in an input video luminance signal, comprising:

• a first minimum value detecting step of detecting in the input video luminance signal a minimum luminance level in a display area;
• a histogram detecting step of detecting an amount of distribution of the input video luminance signal at each luminance level in a luminance level range including the minimum luminance level detected in the first minimum value detecting step and a luminance level adjacent thereto;
• a comparing step of determining, based on the amount of distribution detected in the histogram detecting step, whether the luminance level range includes information which is located at a luminance level away from the original image and is unrelated to the original image;
• a replacing step of replacing, when it is determined in the comparing step that the information unrelated to the original image is included, a luminance level with respect to the unrelated information in the input video luminance signal by a luminance level which unaffects detection of the minimum luminance level of the original image;
• and
• a second minimum value detecting step of detecting a minimum luminance level in an input video signal obtained after the luminance level with respect to the unrelated information is replaced in the replacing step.

An image processing method for obtaining a maximum value signal suitable for dynamic gray-scale correction in motion pictures, comprising:

• an APL detecting step of detecting an average luminance level in a display area of an input video luminance signal;
• an APL varied value detecting step of detecting a varied value at the average luminance level detected in the APL detecting step;
• a maximum value detecting step of detecting a maximum luminance level in the display area of the input video luminance signal;
• and
• a filter step of controlling the maximum luminance level detected in the maximum value detecting step in accordance with the varied value at the average luminance level detected in the AFL varied value detecting step, and producing an output as the maximum value signal, wherein
• the filter step outputs the maximum luminance level as it is when the varied value is larger than a first predetermined value, fixedly outputs a maximum luminance level that is an immediately previous output when the varied value is smaller than a second predetermined value, and outputs the maximum luminance level that follows in accordance with the varied value when the varied value is larger than the second predetermined value and smaller than the first predetermined value.

An image processing method for obtaining a minimum value signal suitable for dynamic gray-scale correction in motion pictures, comprising:

• an APL detecting step of detecting an average luminance level in a display area of an input video luminance signal;
• an APL varied value detecting step of detecting a varied value at the average luminance level detected in the APL detecting step;
• a minimum value detecting step of detecting a minimum luminance level in the display area of the input video luminance signal;
• and
• a filter step of controlling the minimum luminance level detected in the minimum value detecting step in accordance with the varied value at the average luminance level detected in the APL varied value detecting step, and producing an output as the minimum value signal, wherein
• the filter step outputs the minimum luminance level as it is when the varied value is larger than a first predetermined value, fixedly outputs a minimum luminance level that is an immediately previous output when the varied value is smaller than a second predetermined value, and outputs the minimum luminance level that follows in accordance with the varied value when the varied value is larger than the second predetermined value and smaller than the first predetermined value.