Method and system for real-time equirectangular projection

• US 9,984,436 B1
• Filed: 03/04/2016
• Issued: 05/29/2018
• Est. Priority Date: 03/04/2016
• Status: Expired due to Fees

• Current Assignee: Scott Zhihao Chen
• Original Assignee: Scott Zhihao Chen
• Inventors: Chen, Scott Zhihao
• Primary Examiner(s): Villecco, John
• Application Number:
  US15/061,900
• Time in Patent Office: 816 Days
• CPC Class Codes: G06T 1/60 Memory management
• CPC Class Codes: G06T 2207/20021 Dividing image into blocks, subimages or windows
• CPC Class Codes: G06T 3/047 Fisheye or wide-angle transformations
• CPC Class Codes: G06T 3/08 Projecting images onto non-planar surfaces, e.g. geodetic screens
• CPC Class Codes: G06T 3/18 Image warping, e.g. rearranging pixels individually
• CPC Class Codes: G06V 10/20 Image preprocessing
• CPC Class Codes: G06V 10/247 by affine transforms, e.g. correction due to perspective effects; Quadrilaterals, e.g. trapezoids
• CPC Class Codes: H04N 23/63 by using electronic viewfinders
• CPC Class Codes: H04N 23/698 for achieving an enlarged field of view, e.g. panoramic image capture

Abstract

A system and machine-implemented method of real-time equirectangular projection are provided. A first macro-block in an equirectangular projection lookup table is retrieved. A second macro-block of pixels corresponding to the first macro-block determined by pixel mapping information of the first macro-block is retrieved. Destination coordinates of the pixels in the second macro-block by the pixel mapping information is determined. Pixel values of the pixels in the second macro-block to the corresponding destination coordinates are provided for output.

Claims

1. A machine-implemented method for real-time equirectangular projection, comprising:

retrieving a macro-block in an equirectangular projection lookup table;

retrieving a block of pixels corresponding to the macro-block determined by pixel mapping information of the macro-block;

determining destination coordinates of the pixels in the block by the pixel mapping information; and

providing for output pixel values of the pixels in the block to the corresponding destination coordinates.

2. The machine-implemented method of claim 1, further comprising:

dividing a frame of a flat image into a plurality of the blocks of pixels prior to the retrieving the block of pixels; and

storing the plurality of the blocks of pixels in a storage unit.

3. The machine-implemented method of claim 2, further comprising:

retrieving a plurality of the macro-blocks in the equirectangular projection lookup table;

determining an index address of the block of pixels; and

retrieving the block of pixels from the storage unit.

4. The machine-implemented method of claim 3, wherein the pixel mapping information comprises:

an identification of coordinates of the pixels in the block;

original coordinates of the pixels in the block;

coordinates of the block in the frame of the flat image; and

destination coordinates of the pixels in the block.

5. The machine-implemented method of claim 4, further comprising:

confirming whether the identification of coordinates of the pixels in the block is valid;

retrieving the destination coordinates corresponding to the original coordinates determined by the pixel mapping information.

6. The machine-implemented method of claim 5, wherein the providing for output pixel values of the pixels comprises:

calculating a pixel index address for each of the pixels in the block based on the original coordinates of the pixels in the block and coordinates of the block;

retrieving a pixel value from the pixel index address; and

providing for output the pixel value to the destination coordinates.

7. The machine-implemented method of claim 5, wherein the determining the index address of the block of pixels is determined as [(m−

1)*A/a+n−

1]*a*b, and wherein the calculating a pixel index address is determined as a*get_mod(y,a)+x−

a*(n−

1), and wherein m is a x-coordinate of the block in the frame of the flat image, A is a number of pixels in a transverse direction of the frame of the flat image, a is a number of pixels in a transverse direction of the block, n is a y-coordinate of the block in the frame of the flat image, b is a number of pixels in a longitudinal direction of the frame of the flat image, (x,y) is an original coordinate of a pixel in the block, get_mod(y,a) is a modulus operation.

8. A real-time equirectangular projection system comprising:

at least one processor that is configured to;

retrieve a macro-block in an equirectangular projection lookup table, and a block of pixels corresponding to the macro-block determined by pixel mapping information of the macro-block;

map original coordinates of the pixels in the block to destination coordinates of the pixels in the block determined by the pixel mapping information; and

output pixel values of the pixels in the block to the corresponding destination coordinates.

9. The real-time equirectangular projection system of claim 8, further comprising:

a storage unit configured to divide a frame of a flat image into a plurality of the blocks of pixels and store the plurality of the blocks of pixels in a storage unit.

10. The real-time equirectangular projection system of claim 9, wherein the at least one processor is further configured to:

confirm a block index address of the block of pixels corresponding to the macro-block determined by pixel mapping information of the macro-block; and

retrieve the block of pixels from the storage unit based on the block index address.

11. The real-time equirectangular projection system of claim 10, wherein the pixel mapping information comprises:

an identification of coordinates of the pixels in the block;

original coordinates of the pixels in the block;

coordinates of the block in the frame of the flat image; and

destination coordinates of the pixels in the block.

12. The real-time equirectangular projection system of claim 11, wherein the at least one processor is further configured to:

confirm the identification of coordinates of the pixels in the block is valid;

retrieve the destination coordinates of the pixels in the block corresponding to the original coordinates of the pixels in the block determined by the pixel mapping information of the macro-block.

13. The real-time equirectangular projection system of claim 11, wherein the at least one processor is further configured to:

calculate a pixel index address corresponding to a pixel in the block based on the original coordinate of the pixel and the coordinates of the block;

retrieve a pixel value from the pixel index address; and

output the pixel value to the destination coordinates of the pixel.

14. The real-time equirectangular projection system of claim 13, wherein the determining the index address of the block of pixels is determined as [(m−

1)*A/a+n−

1]*a*b, and wherein the calculating a pixel index address is determined as a*get_mod(y,a)+x−

a*(n−

1), and wherein m is a x-coordinate of the block in the frame of the flat image, A is a number of pixels in a transverse direction of the frame of the flat image, a is a number of pixels in a transverse direction of the block, n is a y-coordinate of the block in the frame of the flat image, b is a number of pixels in a longitudinal direction of the frame of the flat image, (x,y) is an original coordinate of a pixel in the block, get_mod(y,a) is a modulus operation.