Image processing apparatus, method and program

• US 20050046902A1
• Filed: 08/27/2004
• Published: 03/03/2005
• Est. Priority Date: 08/28/2003
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Sugimoto, Yusuke
• Granted Patent: US 7,580,158 B2
• Time in Patent Office: Days
• US Class Current: 358/3.10
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/92 based on global image properties
• CPC Class Codes: H04N 1/4074 using histograms

Abstract

An image analysis unit analyzes an image on which AE processing has been performed and obtains a coefficient for obtaining a gradient of a compression table for compressing a dynamic range of the image. A compression table creation unit creates a compression table. A correction amount calculation unit judges whether the gradient of the compression table is larger than a predetermined threshold value. If the judgment is YES, loss of fine texture in the image by dynamic range compression is significant. Therefore, the correction amount calculation unit calculates a correction amount by using an unsharp image of the image. If the judgment is NO, loss of fine texture in the image is insignificant, the correction amount calculation unit calculates the correction amount by using the image. A compression processing unit compresses the dynamic range of the image by the correction amount and obtains a processed image data set.

Claims

1. An image processing apparatus comprising:

a correction amount calculation means for calculating a correction amount to compress a dynamic range of an image based on an image data set representing the image;

a processing means for obtaining a processed image of which the dynamic range has been compressed by performing image processing on the image, including processing for compressing the dynamic range of the image, by correcting the image data set by the correction amount; and

a judgment means for judging whether a change amount of the image by the image processing is larger than a predetermined threshold value, wherein if the judgment is YES, the correction amount calculation means produces an unsharp image of the image and calculates the correction amount by using the unsharp image or if the judgment is NO, the correction amount calculation means calculates the correction amount by using the image.

2. An image processing apparatus as defined in claim 1, wherein the judgment means makes the judgment by using at least one of a value of a compression rate for compressing the dynamic range, a value of a gradient of a compression table which is used for calculating the correction amount, and if the image processing includes AE (Automatic Exposure) processing, a value of a correction amount of density as the change amount of the image.

3. An image processing method comprising the steps of:

calculating a correction amount to compress a dynamic range of an image based on an image data set representing the image;

obtaining a processed image of which the dynamic range has been compressed by performing image processing on the image, including processing for compressing the dynamic range of the image, by correcting the image data set by the correction amount;

judging whether a change amount of the image by the image processing is larger than a predetermined threshold value; and

if the judgment is YES, producing an unsharp image of the image and calculating the correction amount by using the unsharp image or if the judgment is NO, calculating the correction amount by using the image.

4. A program for causing a computer to execute an image processing method, the program comprising the procedures for:

calculating a correction amount to compress a dynamic range of an image based on an image data set representing the image;

obtaining a processed image of which the dynamic range has been compressed by performing image processing on the image, including processing for compressing the dynamic range of the image, by correcting the image data set by the correction amount;

judging whether a change amount of the image by the image processing is larger than a predetermined threshold value; and

if the judgment is YES, producing an unsharp image of the image and calculating the correction amount by using the unsharp image or if the judgment is NO, calculating the correction amount by using the image.

9. A computer readable medium having the program defined in claim 4 recorded therein.

5. An image processing apparatus for obtaining a processed image of which the dynamic range has been compressed by compressing the dynamic range of an image, the apparatus comprising:

a compression table creation means for creating a first compression table to compress the dynamic range of the image and a second compression table to further compress the dynamic range of the image of which the dynamic range has been compressed by using the first compression table;

a first dynamic range compression processing means for obtaining an intermediate processed image by producing an unsharp image of the image, calculating a first correction amount to compress the dynamic range of the image by using the unsharp image and the first compression table and performing first dynamic range compression processing to compress the dynamic range of the image by the first correction amount; and

a second dynamic range compression processing means for obtaining the processed image by calculating a second correction amount to further compress the dynamic range of the image by using the intermediate processed image and the second compression table and performing second dynamic range compression processing to compress the dynamic range of the image by the second correction amount.

6. An image processing apparatus as defined in claim 5, wherein the compression table creation means judges whether the second compression table should be created, and only if the judgment is YES, the compression table creation means creates the second compression table, wherein if the second compression table is not created, the first dynamic range compression processing means outputs the intermediate processed image obtained by the first dynamic range compression processing means as the processed image.

7. An image processing method for obtaining a processed image of which the dynamic range has been compressed by compressing the dynamic range of an image, the method comprising the steps of:

creating a first compression table to compress the dynamic range of the image and a second compression table to further compress the dynamic range of the image of which the dynamic range has been compressed by using the first compression table;

obtaining an intermediate processed image by producing an unsharp image of the image, calculating a first correction amount to compress the dynamic range of the image by using the unsharp image and the first compression table and performing first dynamic range compression processing to compress the dynamic range of the image by the first correction amount; and

obtaining the processed image by calculating a second correction amount to further compress the dynamic range of the image by using the intermediate processed image and the second compression table and performing second dynamic range compression processing to compress the dynamic range of the image by the second correction amount.

8. A program for causing a computer to execute an image processing method for obtaining a processed image of which the dynamic range has been compressed by compressing the dynamic range of the image, the program comprising the procedures for:

creating a first compression table to compress the dynamic range of the image and a second compression table to further compress the dynamic range of the image of which the dynamic range has been compressed by using the first compression table;

obtaining an intermediate processed image by producing an unsharp image of the image, calculating a first correction amount to compress the dynamic range of the image by using the unsharp image and the first compression table and performing first dynamic range compression processing to compress the dynamic range of the image by the first correction amount; and

obtaining the processed image by calculating a second correction amount to further compress the dynamic range of the image by using the intermediate processed image and the second compression table and performing second dynamic range compression processing to compress the dynamic range of the image by the second correction amount.

10. A computer readable medium having the program defined in claim 8 recorded therein.