TONE CORRECTING APPARATUS PROVIDING IMPROVED TONE CORRECTION ON IMAGE

• US 20090060379A1
• Filed: 08/27/2008
• Published: 03/05/2009
• Est. Priority Date: 08/31/2007
• Status: Active Grant

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: MANABE, Yoshitsugu
• Granted Patent: US 8,009,927 B2
• Time in Patent Office: Days
• US Class Current: 382/274
• CPC Class Codes: H04N 23/611 where the recognised objects include parts of the human body
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation

Abstract

A tone correcting apparatus includes: a first acquiring unit that acquires first brightness information indicating brightness of each of a plurality of block regions that are set to cover an entire area of an image; a face detecting unit that detects a face portion where a human face is positioned in the image; a second acquiring unit that acquires second brightness information indicating brightness of the face portion detected by the face detecting unit; and a correction unit that corrects brightness of the image based on the first brightness information and the second brightness information.

Claims

1. A tone correcting apparatus for correcting a tone of an image, the apparatus comprising:

a first acquiring unit that acquires first brightness information indicating brightness of each of a plurality of block regions that are set to cover an entire area of the image;

a face detecting unit that detects a face portion where a human face is positioned in the image;

a second acquiring unit that acquires second brightness information indicating brightness of the face portion detected by the face detecting unit; and

a correction unit that corrects brightness of the image based on the first brightness information and the second brightness information.

2. The apparatus according to claim 1 further comprising a characteristic setting unit that sets a correction characteristic for each of pixels in the image based on the first brightness information and the second brightness information,

wherein the correction unit corrects the brightness of each of the pixels in accordance with the correction characteristic set for the respective pixels by the characteristic setting unit.

3. The apparatus according to claim 2, wherein the correction characteristic setting unit sets, as the correction characteristic, an adjustment characteristic of a correction coefficient with respect to a change in brightness of the respective pixels, and

wherein the correction characteristic setting unit adjusts a maximum value of the adjustment characteristic for the respective pixels in accordance with second brightness information.

4. The apparatus according to claim 3 further comprising a calculation unit that calculates the correction coefficient with a correction function,

wherein the characteristic setting unit sets the correction characteristic for the respective pixels by setting a variable of the correction function based on the first brightness information and the second brightness information.

5. The apparatus according to claim 2, wherein the characteristic setting unit includes:

a first characteristic setting unit that sets a first correction characteristic for a given block region selected from among the block regions, the first correction characteristic being selected from among a plurality of correction characteristics in accordance with the first brightness information for the respective block regions;

a second characteristic setting unit that sets a second correction characteristic for the respective block regions except the given block region, the second correction characteristic being obtained based on the first brightness information and the second brightness information; and

a third characteristic setting unit that sets a third correction characteristic for each of the pixels based on the first correction characteristic and the second correction characteristic.

6. The apparatus according to claim 5, wherein the third characteristic setting unit sets the first correction characteristic for a center pixel in each of the respective block regions and sets a fourth correction characteristic for the pixels except the center pixel, the fourth correction characteristic being obtained by interpolating the first correction characteristic set for at least one of the center pixel that is adjacent to the respective pixels.

7. The apparatus according to claim 1, wherein the first acquiring unit acquires the first brightness information for the respective block regions based on a V value, in an HSV color space, of the pixels included in the respective block regions, and

wherein the second acquiring unit acquires the second brightness information for the face portion based on a Y value, in a YUV color space, of the pixels included in the face portion.

8. The apparatus according to claim 1, wherein the correction unit corrects the brightness of each of the pixels included in a face block, which includes at least one of the block regions that overlaps the face portion, based on the first brightness information and the second brightness information.

9. The apparatus according to claim 8, wherein each of the first brightness information and the second brightness information indicate a brightness level of the respective block regions and the face portion,

wherein the apparatus further comprises a third acquiring unit that acquires an average level by averaging the brightness levels of the block regions that belong to the face block based on pixel information indicating information of the pixels in the image,

wherein the correction unit includes a comparing unit that compares the brightness level acquired by the second acquiring unit and the average level acquired by the third acquiring unit, and

wherein the correction unit corrects the brightness of each of the pixels included in the face block based on a result of the comparison by the correction unit.

10. The apparatus according to claim 9, wherein the correction unit includes an adjustment unit that operates to:

increase the brightness of the block regions that belong to the face block when the comparing unit compares that the brightness level acquired by the second acquiring unit is higher than the average level acquired by the third acquiring unit; and

decrease the brightness of the block regions that belong to the face block when the comparing unit compares that the brightness level acquired by the second acquiring unit is lower than the average level acquired by the third acquiring unit.

11. The apparatus according to claim 8, the first acquiring unit acquires the first brightness information for the respective block regions based on a V value, in an HSV color space, of the pixels included in the respective block regions, and

wherein the second acquiring unit acquires the second brightness information for the face portion based on a Y value, in a YUV color space, of the pixels included in the face portion.

12. The apparatus according to claim 1 further comprising a determination unit that determines whether or not the face portion is detected in the image by the detecting unit,

wherein the correction unit corrects brightness of the image based on the first brightness information and the second brightness information when the determination unit determines that the face portion is detected by the detecting unit.

13. The apparatus according to claim 1 further comprising:

a first determination unit that determines which one of first brightness levels that are previously defined a focused region corresponds to, the focused region being selected from among the block regions; and

a second determination unit that determines which one of second brightness levels that are previously defined an adjacent block region corresponds to, the adjacent block region being at least one of the block regions that is adjacent to the focused region,

wherein the first acquiring unit acquires the brightness of the focused region based on a combination of the first brightness level determined by the first determination unit and the second brightness level determined by the second determination unit.

14. A method for correcting a tone of an image, the method comprising:

acquiring first brightness information indicating brightness of each of a plurality of block regions that are set to cover an entire area of the image;

detecting a face portion where a human face is positioned in the image;

acquiring second brightness information indicating brightness of the face portion; and

correcting brightness of the image based on the first brightness information and the second brightness information.

15. A computer-readable storage medium containing a sequence of instructions for a program executable by a computer for correcting a tone of an image, the program comprising:

instructions for acquiring first brightness information indicating brightness of each of a plurality of block regions that are set to cover an entire area of the image;

instructions for detecting a face portion where a human face is positioned in the image;

instructions for acquiring second brightness information indicating brightness of the face portion; and

instructions for correcting brightness of the image based on the first brightness information and the second brightness information.