Image processing method and apparatus

• US 6,415,053 B1
• Filed: 04/20/1999
• Issued: 07/02/2002
• Est. Priority Date: 04/20/1998
• Status: Expired due to Fees

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Norimatsu, Masashi
• Primary Examiner(s): Couso, Jose L.
• Assistant Examiner(s): DESIRE, GREGORY M
• Application Number:
  US09/294,996
• Time in Patent Office: 1,169 Days
• Field of Search: 382/132, 382/154, 382/199, 382/260-267, 382/162, 382/190, 382/197, 382/204, 382/266, 382/274, 348/607, 348/625
• US Class Current: 382/199
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/20012 Locally adaptive
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 2207/20204 Removing film grain; Adding simulated film grain
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: G06T 5/73 Deblurring; Sharpening
• CPC Class Codes: G06T 7/12 Edge-based segmentation
• CPC Class Codes: H04N 1/4092 Edge or detail enhancement
• CPC Class Codes: H04N 1/58 Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction H04N1/62 takes precedence

Abstract

The image processing method and apparatus calculate and store gradients representing directions and intensities of a pixel of interest and its surrounding pixels from pixel values of the pixel of interest and its surrounding pixels of image composed of the color image signals that are to be subjected to image processing, calculate connectivity of the pixel of interest with its surrounding pixels from the directions of the stored gradients, calculate directivities of respective R, G and B of the pixel of interest by calculating gradients of respective R, G and B channels of the pixel of interest and decide whether the pixel of interest is an edge portion or not from the calculated connectivity and directivities of respective R, G and B to extract the edge portion. As a result, the method and the apparatus can raise extraction precision of the edge portion, accurately perform the edge portion extraction and increase image quality. Moreover, the method and apparatus calculate correction-amounts of degree of sharpness enhancement and granularities of a plurality of the specified regions formed by dividing the image data based on the extraction result of the edge portion and correct the image data based on these correction amounts. Accordingly, careful and minute corrections of granularity and degree of sharpness enhancement can be performed on the image recorded in one frame.

Claims

1. An image processing method for subjecting digital image data of color image signals to specified image processing, comprising the steps of:

calculating gradients representing directions and intensities of a pixel of interest and its surrounding pixels from pixel values of said pixel of interest and its surrounding pixels of image composed of said color image signals that are to be subjected to image processing;

storing the calculated gradients;

calculating connectivity of said pixel of interest with its surrounding pixels from the directions of said stored gradients;

calculating directivities of respective R, G and B of said pixel of interest by calculating gradients of respective R, G and B channels of said pixel of interest; and

deciding whether said pixel of interest is an edge portion or not from said connectivity and said directivities of respective R, G and B to extract said edge portion.

2. The image processing method according to claim 1, wherein, when said connectivity of said pixel of interest with its surrounding pixels is calculated, a direction of gradient of said pixel of interest and directions of gradients of nearby pixels of said pixel of interest are compared, and thereby, if the directions of a specified number of said nearby pixels agree with a specified condition, it is decided that the connectivity exists.

3. The image processing method according to claim 2, wherein said specified condition with which the directions of the specified number of said nearby pixels agree is a condition that 50% or more of the directions of said nearby pixels are within 45 degrees from the direction of said pixel of interest.

4. The image processing method according to claim 2, wherein said nearby pixels are referred to any one of 1×

3 pixels, 1×

5 pixels, 3×

5 pixels and 3×

7 pixels excluding the pixel of interest placed in center of each of above pixel configurations where more pixels are arranged in the direction perpendicular to the direction of gradient of said pixel of interest than the direction of gradient.

5. The image processing method according to claim 2, wherein deciding conditions of the connectivity of the pixel including a way of selecting said nearby pixels, said specified number of said nearby pixels whose directions agree with said specified condition and said specified condition with which the directions of said specified number of the adjacent pixels agree are determined in accordance with at least one of an original kind, an original size, a print magnification, a camera kind and an exposure condition.

6. The image processing method according to claim 1, wherein, when said connectivity of said pixel of interest with its surrounding pixels is calculated, if the directions of gradient of the adjacent pixels that are located on opposite sides of said pixel of interest in a direction of 90 degrees from the direction of gradient of said pixel of interest are within 45 degrees , it is decided that the connectivity exists.

7. The image processing method according to claim 1, wherein said gradients of said pixel of interest and its surrounding pixels based on said color image signals are calculated based on a luminance signal of said color image signals.

8. The image processing apparatus according to claim 1, further comprising the steps of:

calculating at least one correction amount of a degree of sharpness enhancement and a granularity in each of a plurality of specified regions based on whether said plurality of the specified regions formed by dividing said image data include said edge portion or not;

correcting at least one of said degree of the sharpness enhancement and said granularity of said image data based on the calculated correction amount of each specified region; and

subjecting said image data to specified image processing including correction of at least one of said degree of the sharpness enhancement and said granularity to produce output image data.

9. The image processing apparatus according to claim 8, further comprising the step of calculating a correction amount of said granularity in each of a plurality of specified regions based on each density of said plurality of the specified regions formed by dividing said image data.

10. An image processing apparatus for subjecting digital image data of color image signals to specified image processing, comprising:

calculating means for calculating gradients of a pixel of interest and its surrounding pixels that represent directions and intensities of an edge from pixel values of said pixel of interest and its surrounding pixels of image composed of said color image signals that are to be subjected to image processing;

storing means for storing said calculated gradients;

calculating means for calculating connectivity of said pixel of interest with its surrounding pixel from the directions of said stored gradients;

calculating means for calculating directivities of respective R, G and B of said pixel of interest by calculating gradients of respective R, G and B channels of said pixel of interest; and

deciding means for deciding whether said pixel of interest is an edge portion or not from said connectivity and the directivities of respective R, G and B, thereby edge portion extraction is performed.

11. The image processing apparatus according to claim 10, wherein said calculating means for calculating the connectivity of the pixel of interest with its surrounding pixel is to compare a direction of gradient of said pixel of interest and directions of gradients of nearby pixels, and wherein, if the directions of a specified number of said nearby pixels agree with a specified condition, it is decided that the connectivity exists.

12. The image processing apparatus according to claim 11, wherein said specified condition with which the directions of the specified number of said nearby pixels agree is a condition that 50% or more of the directions of said nearby pixels are within 45 degrees from the direction of said pixel of interest.

13. The image processing apparatus according to claim 11, wherein said nearby pixels are referred to any one of 1×

3 pixels, 1×

5 pixels, 3×

5 pixels and 3×

7 pixels excluding the pixel of interest placed in center of each of above pixel configurations where more pixels are arranged in the direction perpendicular to the direction of gradient of said pixel of interest than the direction of gradient.

14. The image processing apparatus according to claim 11, wherein deciding conditions of the connectivity of the pixel including a way of selecting said nearby pixels, said specified number of said nearby pixels whose directions agree with said specified condition and said specified condition with which the directions of said specified number of the nearby pixels agree are determined in accordance with at least one of an original kind, an original size, a print magnification, a camera kind and an exposure condition.

15. The image processing apparatus according to claim 10, wherein said calculating means for calculating the connectivity of the pixel of interest with its surrounding pixels decides that the connectivity exists, if the directions of gradients of the adjacent pixels that are located on opposite sides of said pixel of interest in a direction of 90 degrees from the direction of the gradient of said pixel of interest are both within 45 degrees from the direction of the gradient of said pixel of interest.

16. The image processing apparatus according to claim 10, wherein said gradients of said pixel of interest and its surrounding pixels based on said color image signals are calculated based on a luminance signal of said color image signals.

17. The image processing apparatus according to claim 10, further comprising:

sharpness enhancement degree correction amount calculating means for calculating a correction amount of a degree of sharpness enhancement in each specified region, based on whether a plurality of specified regions formed by dividing said image data include said edge portion or not; and

sharpness enhancement degree correction means for correcting said degree of the sharpness enhancement of said image data based on the calculated correction amount of each specified region by said sharpness enhancement degree correction amount calculating means, wherein said image data is subjected to specified image processing including correction of said degree of the sharpness enhancement to produce output image data.

18. The image processing apparatus according to claim 17, further comprising:

granularity correction amount calculating means for calculating a correction amount of a granularity in each specified region based on each density of said plurality of the specified regions; and

granularity correction means for correcting the granularity of said image data based on the correction amount of each specified region calculated by said granularity correction amount calculating means.

19. The image processing apparatus according to claim 18, wherein said granularity correction amount calculating means further calculates a correction amount of the granularity in each specified region based on whether said plurality of said specified regions include the edge portion or not.

20. The image processing apparatus according to claim 10, further comprising:

granularity correction amount calculating means for calculating a correction amount of a granularity in each specified region based on whether a plurality of specified regions formed by dividing said image data include the edge portion or not; and

granularity correction means for correcting the granularity of said image data based on the correction amount of each specified region calculated by said granularity correction amount calculating means.