Determining target luminance value of an image using predicted noise amount

• US 8,035,871 B2
• Filed: 01/30/2009
• Issued: 10/11/2011
• Est. Priority Date: 06/17/2004
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Kameyama, Hirokazu
• Primary Examiner(s): Tieu; Benny
• Assistant Examiner(s): Rust; Eric A
• Application Number:
  US12/362,759
• Publication Number:
  US 20090136152A1
• Time in Patent Office: 984 Days
• Field of Search: 358/3.23, 358/520, 358/500, 348/234, 382/167
• US Class Current: 358/520
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence

Abstract

A bright luminance value, a dark luminance value, and an average luminance value relating to a face image portion included in an image represented by fed image data are calculated in calculating circuits. Further, a target bright luminance value and a target dark luminance value are calculated in a calculating circuit on the basis of a target average luminance value and a dynamic range that are inputted from an input device and the calculated bright luminance value, dark luminance value, and average luminance value. Interpolation processing based on a correspondence between the calculated bright luminance value, dark luminance value, and average luminance value relating to the face image portion and the target bright luminance value, the target dark luminance value, and the target average luminance value respectively corresponding thereto is performed in a corrected value calculating circuit, to create a look-up table.

Claims

1. An image correcting apparatus comprising:

representative luminance value calculation circuit for calculating a representative luminance value in a particular image included in an image represented by fed image data;

noise amount calculation circuit for calculating a noise amount included in particular image data representing the particular image;

target luminance value determination circuit for determining a target luminance value depending on the noise amount calculated by the noise amount calculation circuit;

circuit for producing data representing a luminance conversion straight line or a luminance conversion curve such that the represented luminance value calculated by the representative luminance value calculation circuit is corrected to the target luminance value determined by the target luminance value determination circuit; and

luminance correction circuit for correcting the luminance of at least the particular image data representing the particular image on the basis of the produced data representing the luminance conversion straight line or the luminance conversion curve; and

comprising

desired target luminance value input circuit for accepting input of a desired target luminance value, and

predicted noise amount calculation circuit for calculating a predicted noise amount that may be included in the particular image data after luminance correction on the basis of the representative luminance value calculated by the representative luminance value calculation circuit, the desired target luminance value inputted by the target luminance value input circuit and the noise amount calculated by the noise amount calculation circuit,

the target luminance value determination circuit determining the target luminance value depending on the predicted noise amount calculated by the predicted noise amount calculation circuit.

2. The image correcting apparatus according to claim 1, wherein

the target luminance value determination circuit determines, on the basis of an allowable noise amount for noise that may be included in the particular image data after luminance correction and the calculated noise amount or the calculated predicted noise amount, that are previously set or inputted, the target luminance value such that the noise amount or the predicted noise amount is not more than the allowable noise amount.

3. The image correcting apparatus according to claim 2, wherein

the target luminance value determination circuit

determines the desirable target luminance value inputted from the desirable target luminance value input circuit as the target luminance value when the calculated predicted noise amount is not more than the allowable noise amount, and

calculates, when the calculated predicted noise amount exceeds the allowable noise amount, such a new target luminance value that the predicted noise amount is the same as the allowable noise amount on the basis of the representative luminance value, the allowable noise amount, and the noise amount, and determines the calculated new target luminance value as the target luminance value.

4. The image correcting apparatus according to claim 1, wherein said particular image is an image representing the face of a character.

5. The image correcting apparatus according to claim 1, wherein the representative luminance value is the average luminance value in the particular image.

6. An image correcting method comprising the steps of:

using at least one processor for performing;

calculating a representative luminance value in a particular image included in an image represented by fed image data;

calculating a noise amount included in particular image data representing the particular image;

determining a target luminance value depending on the calculated noise amount;

producing data representing a luminance conversion straight line or a luminance conversion curve such that the calculated representative luminance value is corrected to the determined target luminance value; and

correcting the luminance of at least the particular image data representing the particular image on the basis of the produced data representing the luminance conversion straight line or the luminance conversion curve; and

further comprising

accepting input of a desired target luminance value, and

calculating a predicted noise amount that may be included in the particular image data after luminance correction on the basis of the representative luminance value calculated by the representative luminance value calculation means, the desired target luminance value inputted by the target luminance value input means, and the noise amount calculated by the noise amount calculation means,

determining the target luminance value depending on the predicted noise amount calculated by the predicted noise amount calculation.

7. A non-transitory computer-readable storage medium for causing a computer to carry out the procedures for:

calculating a representative luminance value in a particular image included in an image represented by fed image data;

calculating a noise amount included in particular image data representing the particular image;

determining a target luminance value depending on the calculated noise amount;

producing data representing a luminance conversion straight line or a luminance conversion curve such that the calculated representative luminance value is corrected to the determined target luminance value; and

correcting the luminance of at least the particular image data representing the particular image on the basis of the produced data representing the luminance conversion straight line or the luminance conversion curve; and

accepting input of a desired target luminance value, and

calculating a predicted noise amount that may be included in the particular image data after luminance correction on the basis of the representative luminance value calculated by the representative luminance value calculation means, the desired target luminance value inputted by the target luminance value input means, and the noise amount calculated by the noise amount calculation means,

determining the target luminance value depending on the predicted noise amount calculated by the predicted noise amount calculation means.