Method and system for adjusting image brightness based on color saturation components

• US 7,081,923 B1
• Filed: 03/17/1999
• Issued: 07/25/2006
• Est. Priority Date: 03/17/1998
• Status: Expired due to Fees

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Noguchi, Takafumi
• Primary Examiner(s): Ometz, David
• Assistant Examiner(s): WHIPKEY, JASON T
• Application Number:
  US09/271,259
• Time in Patent Office: 2,687 Days
• Field of Search: 348/222.1, 348/223.1, 348/224.1, 348/241, 348/242, 348/252, 348253-256, 348/272, 348/273, 348/279, 348/280, 348/645, 348/646, 358518-523, 382/162, 382/166, 382/167, 345/589, 345/591, 345/600
• US Class Current: 348/256
• CPC Class Codes: H04N 1/4072 dependent on the contents of the original
• CPC Class Codes: H04N 1/6027 Correction or control of colour gradation or colour contrast H04N1/6058 takes precedence
• CPC Class Codes: H04N 9/77 Circuits for processing the brightness signal and the chrominance signal relative to each other, e.g. adjusting the phase of the brightness signal relative to the colour signal, correcting differential gain or differential phase circuits for matrixing H04N9/67

Abstract

A method for adjusting image brightness is conducted by a system for adjusting image brightness. Digital image data acquired by a data acquisition unit are sent to a lightness computing unit and a color saturation computing unit that compute the lightness L and the color saturation C for every pixel and sends the computed values to a mean value computing unit. The mean value computing unit weights the lightness L by the color saturation C and computes weighted mean values Lm of the lightnesses L. A converter 5 converts the R, G, B color signal components constituting the digital image data S to make the weighted mean values Lm desired values.

Claims

1. A method for adjusting image brightness comprising the steps of:

effecting a computation on color image data represented by a color signal composed of at least three components to obtain pixel lightness components and an average brightness of an image;

adjusting brightness of the image represented by the color image data based on the lightness components; and

adjusting the brightness of the image represented by the color image data based on the average brightness of the image,

wherein the average brightness of the image is adjusted with color saturation components of the pixels, and

wherein the step of adjusting the brightness of the image represented by the color image data based on color saturation components of the pixels is effected by computing weighted lightness components by weighting the lightness components of the pixels by the color saturation components of the pixels, computing mean values of the weighted lightness components, and adjusting the brightness by converting the color image data to make the mean values desired values.

2. The method of claim 1, wherein the average brightness of the image is obtained by any one of the following:

averaging the color saturation components of the pixels to obtain an average color saturation value, adjusting the lightness components of the image based on the average color saturation value to obtain an average lightness value, and designating the average lightness value as the average brightness of the image;

averaging the color saturation components of the pixels to obtain the average color saturation value, selecting pixels to be used to calculate the average lightness value based on the average color saturation value, averaging the lightness values of the selected pixels to obtain the average lightness value, and designating the average lightness value as the average brightness of the image; and

averaging and obtaining a variance of the color saturation components of the pixels to obtain the average color saturation value and the variance, selecting pixels to be used to calculate the average lightness value based on the average color saturation value and the variance, averaging the lightness values of the selected pixels to obtain the average lightness value, and designating the average lightness value as the average brightness of the image.

3. A system for adjusting image brightness comprising an adjuster having an adjustment unit configured for effecting a computation on color image data represented by a color signal composed of at least three components to obtain pixel lightness components and an average brightness of an image and adjusting brightness of the image represented by the color image data based on the lightness components, the system being characterized in that the adjustment unit is further configured for adjusting the brightness of the image represented by the color image data based on the average brightness of the image, wherein the average brightness of the image is adjusted with color saturation components of the pixels,

wherein the adjuster includes weighted lightness component computing means for computing weighted lightness components of the pixels by weighting the lightness components of the pixels by the color saturation components of the pixels, mean value computing means for computing mean values of the weighted lightness components, and conversion means for converting the color image data to make the mean values desired values.

4. The system of claim 3, wherein the adjustment unit is configured to obtain the average brightness of the image is by any one of the following:

averaging the color saturation components of the pixels to obtain an average color saturation value, adjusting the lightness components of the image based on the average color saturation value to obtain an average lightness value, and designating the average lightness value as the average brightness of the image;

averaging the color saturation components of the pixels to obtain the average color saturation value, selecting pixels to be used to calculate the average lightness value based on the average color saturation value, averaging the lightness values of the selected pixels to obtain the average lightness value, and designating the average lightness value as the average brightness of the image; and

averaging and obtaining a variance of the color saturation components of the pixels to obtain the average color saturation value and the variance, selecting pixels to be used to calculate the average lightness value based on the average color saturation value and the variance, averaging the lightness values of the selected pixels to obtain the average lightness value, and designating the average lightness value as the average brightness of the image.

5. A device for adjusting brightness of an image, comprising:

a data acquisition unit configured to acquire image data of the image; and

an adjustment unit configured to adjust a brightness of the image based on an average brightness of the image, wherein the average brightness of the image is adjusted with a color saturation of the image data from said data acquisition unit,

wherein the adjustment unit comprises;

a lightness computing unit configured to compute lightness of the image data;

a color saturation computing unit configured to compute color saturation of the image data;

a mean value computing unit configured to compute mean values of the lightness computed by the lightness computing unit based on the colour saturation computed by the color saturation unit; and

a converting unit configured to convert the brightness of the image data based on the mean values computed by the mean value computing unit.

6. The device of claim 5, wherein:

the lightness computing unit is configured to compute the lightness of the image data on an individual pixel basis;

the color saturation computing unit is configured to compute color saturations of the individual pixels; and

the converting unit is configured to convert the brightness of the image data on individual pixel basis.

7. The device of claim 5, wherein the converting is configured to achieve a predetermined brightness reflectance value.

8. The device of claim 7, wherein the predetermined brightness reflectance value is substantially 18%.

9. The device of claim 5, wherein the lightness computing unit is configured to determine lightness on the basis of at least one of mean values of individual color components, maximum values of individual color components, and brilliance of individual color components.

10. The device of claim 5, wherein the color saturation computing unit is configured to determine color saturation on the basis of at least one of ratios between maximum individual color components and minimum individual color components and the differences between maximum individual color components and the minimum individual color components.

11. The device of claim 5, wherein the mean value computing unit is configured to determine mean values on the basis of at least one of a whole image, a center portion of the image, and one or more specific regions of the image.

12. The system of claim 5, wherein the adjustment unit is configured to obtain the average brightness of the image is by any one of the following:

averaging the color saturation components of the pixels to obtain an average color saturation value, adjusting the lightness components of the image based on the average color saturation value to obtain an average lightness value, and designating the average lightness value as the average brightness of the image;

averaging the color saturation components of the pixels to obtain the average color saturation value, selecting pixels to be used to calculate the average lightness value based on the average color saturation value, averaging the lightness values of the selected pixels to obtain the average lightness value, and designating the average lightness value as the average brightness of the image; and

averaging and obtaining a variance of the color saturation components of the pixels to obtain the average color saturation value and the variance, selecting pixels to be used to calculate the average lightness value based on the average color saturation value and the variance, averaging the lightness values of the selected pixels to obtain the average lightness value, and designating the average lightness value as the average brightness of the image.

13. A method for adjusting brightness of an image, comprising:

acquiring image data of the image; and

adjusting a brightness of the image based on an average brightness of the image, wherein the average brightness of the image is adjusted with a color saturation of the image data, wherein the adjusting step comprises;

computing lightness of the image data;

computing color saturation of the image data;

computing mean values of the lightness of the image data; and

converting the brightness of the image data based on the mean values of the lightness of the image data.

14. The method of claim 13, wherein:

the computing lightness step comprises computing the lightness of the image data on individual pixel basis;

the computing color saturation step comprises computing color saturations of the individual pixels; and

the converting step comprises converting the brightness of the image data on individual pixel basis.

15. The method of claim 13, wherein the converting step comprises converting to achieve a predetermined brightness reflectance value.

16. The method of claim 15, wherein the predetermined brightness reflectance value is substantially 18%.

17. The method of claim 13, wherein the computing the lightness step comprises at least one of:

determining mean values of individual color components;

determining maximum values of individual color components; and

determining brilliance of individual color components.

18. The method of claim 13, wherein the computing color saturation step comprises at least one of:

determining ratios between maximum individual color components and minimum individual color components; and

determining the differences between maximum individual color components and the minimum individual color components.

19. The method of claim 13, wherein the computing the mean values step comprises at least one of:

determining mean values on an entirety of the image;

determining mean values on a center portion of the image; and

determining mean values on one or more specific regions of the image.

20. The method of claim 13, wherein the average brightness of the image is obtained by any one of the following:

averaging the color saturation components of the pixels to obtain an average color saturation value, adjusting the lightness components of the image based on the average color saturation value to obtain an average lightness value, and designating the average lightness value as the average brightness of the image;

averaging the color saturation components of the pixels to obtain the average color saturation value, selecting pixels to be used to calculate the average lightness value based on the average color saturation value, averaging the lightness values of the selected pixels to obtain the average lightness value, and designating the average lightness value as the average brightness of the image; and

averaging and obtaining a variance of the color saturation components of the pixels to obtain the average color saturation value and the variance, selecting pixels to be used to calculate the average lightness value based on the average color saturation value and the variance, averaging the lightness values of the selected pixels to obtain the average lightness value, and designating the average lightness value as the average brightness of the image.