Method for object size and rotation estimation based on log-polar space

• US 20190333243A1
• Filed: 12/27/2017
• Published: 10/31/2019
• Est. Priority Date: 08/11/2017
• Status: Active Grant

• Current Assignee: Zhejiang University
• Original Assignee: Zhejiang University
• Inventors: Zhu, Jianke, Li, Yang
• Granted Patent: US 10,818,032 B2
• Time in Patent Office: Days
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/20056 Discrete and fast Fourier transform, [DFT, FFT]
• CPC Class Codes: G06T 7/248 involving reference images or patches
• CPC Class Codes: G06T 7/60 Analysis of geometric attributes
• CPC Class Codes: G06T 7/62 of area, perimeter, diameter or volume
• CPC Class Codes: G06T 7/73 using feature-based methods
• CPC Class Codes: G06T 7/74 involving reference images or patches

Abstract

The present invention discloses a method which comprises the following steps: inputting the image waiting for test and the template; log-polar transforming the image waiting for test; performing feature extraction on transformed image object; capturing an image feature; achieving a response map of scale and rotation of the image object corresponding to a template through a phase correlation by using features extracted from the image features; calculating a relative displacement by using a response value and coordinates of the response value in a surround area of a maximum value of the response pattern; calculating the scale and the rotation of an object in the image waiting for test corresponding to the template through the relative displacement. The present invention adopts the log-polar space as the image operating space to estimate the change in size and rotation of the object and provide a fast and robust select for upper applications.

Claims

1. A method estimating scale and rotation changes of a visual object in a sequence based on a log-polar space, comprising steps of:

1) inputting an image waiting for test and an image template, log-polar transforming the image waiting for test;

2) performing feature extraction on a transformed image;

capturing an image feature;

3) achieving a response map of a scale and a rotation of the image object corresponding to a template through a phase correlation by using features extracted from the image feature;

4) calculating a relative displacement by using a response value and coordinates of the response value in a surround area of a maximum value of the response map; and

5) calculating the scale and the rotation of an object in the image waiting for test corresponding to the template through the relative displacement.

2. The method estimating the scale and rotation changes of the visual object in the sequence based on log-polar space, as recited in claim 1, wherein an origin of a log-polar transform in the step 1) is a geometric center of an object in an image.

3. The method estimating the scale and rotation changes of the visual object in the sequence based on log-polar space, as recited in claim 1, wherein the image feature in the step 2) is image gradients.

4. The method estimating the scale and rotation changes of the visual object in sequence based on log-polar space, as recited in claim 1, wherein the step 3) further comprises the following sub-steps of:

3.1) calculating with a following formula;

5. The method estimating scale and rotation changes of the visual object in sequence based on log-polar space, as recited in claim 1, wherein the template is a certain image feature or an average of a series of image features.

6. The method estimating the scale and rotation changes of the visual object in sequence based on log-polar space, as recited in claim 1, wherein the step 4) further comprises the following steps:

adopting the response value of the surround area of the maximum value as a weight of coordinates in the surround area of the maximum value;

weighting the coordinates before subtracting the coordinates of the origin in the response map; and

interpolating the coordinates to estimate the relative displacement with floating points by following processing formulas;

7. The method estimating the scale and rotation changes of the visual object in sequence based on log-polar space, as recited in claim 1, wherein the step 5) calculates a relative change of the scale and rotation of the object achieved by normalizing a displacement of the vertical and horizontal coordinates.

8. The method estimating the scale and rotation changes of the visual object in sequence based on log-polar space, as recited in claim 1, wherein the step 5) further comprises the following sub-steps:

normalizing the relative displacement achieved in the step

     4);

calculating a variation of a relative scale and a relative rotation of the object by adopting following formulas;