METHOD FOR BRIGHTNESS EQUALIZATION OF VARIOUS IMAGES

• US 20140341467A1
• Filed: 04/18/2014
• Published: 11/20/2014
• Est. Priority Date: 05/14/2013
• Status: Active Grant

• Current Assignee: Hyundai Mobis Co., Ltd.
• Original Assignee: Hyundai Mobis Co., Ltd.
• Inventors: Seo, Ji Won
• Granted Patent: US 9,135,688 B2
• Time in Patent Office: Days
• US Class Current: 382/167
• CPC Class Codes: G06T 2207/30264 Parking
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 5/94 based on local image properties, e.g. for local contrast enhancement

Abstract

The present invention provides a method for brightness equalization of a plurality of images to equalize brightness when composing, into a single image, a plurality of images acquired from a plurality of cameras.

Claims

1. A method for brightness equalization of a plurality of images, the method comprising:

receiving at least two input images;

composing the at least two input images into a single composite image;

setting a correction area corresponding to each input image in the composite image, and calculating a brightness histogram of each correction area;

calculating a representative value of at least one modal in the brightness histogram, and grouping a modal of each correction area based on the representative value;

calculating a correction target value of each group based on a representative value of modals grouped into each group;

calculating a corrected value by subtracting the representative value of modals of each group of each correction area from the correction target value of each group; and

correcting brightness by adding the corrected value to a pixel value of each group of each correction area.

2. The method of claim 1, wherein, in the composing, a correction and flatness is performed on distortion.

3. The method of claim 1, wherein the brightness histogram is calculated in the entire area corresponding to each input image in the composite image or calculated in an area in which the input images are adjacent to each other in the composite image.

4. The method of claim 3, wherein a quantization level is lowered to simplify a shape of the brightness histogram.

5. The method of claim 1, wherein the modal is a curve in a parabolic shape including at least one peak value between at least two bottom values.

6. The method of claim 1, wherein the representative value of each modal is calculated as any one of an average brightness value and a maximum value of pixels of each modal.

7. The method of claim 6, wherein the average brightness value of pixels of each modal is a value obtained by multiplying each x-axial value of each modal by a y-axial value corresponding to each x-axial value, adding up the multiplication result, and dividing the addition result by all the y-axial values corresponding to x-axial values.

8. The method of claim 1, wherein the correction target value is calculated as any one of an average value of representative values of modals grouped into each group, a representative value of a modal having a widest area, and a representative value of a modal having a highest peak value.

9. A method for brightness equalization of a plurality of images, the method comprising:

receiving at least two input images;

setting a correction area in each input image, and calculating a brightness histogram of each correction area;

calculating a representative value of at least one modal in the brightness histogram, and grouping a modal of each correction area based on the representative value;

calculating a correction target value of each group based on a representative value of modals grouped into each group;

calculating a corrected value by subtracting the representative value of modals of each group of each correction area from the correction target value of each group;

correcting brightness by adding the corrected value to a pixel value of each group of each correction area, and creating at least two corrected images; and

composing the at least two corrected images into a single composite image.

10. The method of claim 9, wherein the brightness histogram is calculated in the entire area of each input image or calculated in an area to be used for composition in each input image.

11. The method of claim 10, wherein a quantization level is lowered to simplify a shape of the brightness histogram.

12. The method of claim 9, wherein the modal is a curve in a parabolic shape including at least one peak value between at least two bottom values.

13. The method of claim 9, wherein the representative value of each modal is calculated as any one of an average brightness value and a maximum value of pixels of each modal.

14. The method of claim 13, wherein the average brightness value of pixels of each modal is a value obtained by multiplying each x-axial value of each modal by a y-axial value corresponding to each x-axial value, adding up the multiplication result, and dividing the addition result by all the y-axial values corresponding to x-axial values.

15. The method of claim 9, wherein the correction target value is calculated as any one of an average value of representative values of modals grouped into each group, a representative value of a modal having a widest area, and a representative value of a modal having a highest peak value.

16. The method of claim 9, wherein, in the composing, a correction and flatness is performed on distortion.