Method and system for calculating a transformed image from a digital image

• US 7,356,198 B2
• Filed: 06/05/2002
• Issued: 04/08/2008
• Est. Priority Date: 07/12/2001
• Status: Expired due to Term

• Current Assignee: Lens Correction Technologies Corporation
• Original Assignee: DXO Labs
• Inventors: Chauville, Benoit, Guichard, Frederic, Lavest, Jean-Marc, Liege, Bruno
• Primary Examiner(s): Ahmed, Samir
• Assistant Examiner(s): Rush, Eric
• Application Number:
  US10/483,252
• Publication Number:
  US 20040247195A1
• Time in Patent Office: 2,134 Days
• Field of Search: 382/297, 382/267, 382/293, 382/254, 382/255, 382/275, 382/283, 348/231.6
• US Class Current: 382/275
• CPC Class Codes: G06T 1/0007 Image acquisition
• CPC Class Codes: H04N 1/387 Composing, repositioning or otherwise geometrically modifying originals
• 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 invention relates to a system and method for calculating a transformed image from a digital image and formatted information related to a geometric transformation, especially formatted information related to the distortion and/or chromatic aberrations of an appliance chain. This calculation is carried out on the basis of an approximation of the said geometric transformation. The invention is applicable to photographic or video image processing, in optical devices, industrial controls, robotics, metrology, etc.

Claims

1. A method for calculating a transformed image from a digital image and formatted information related to a geometric transformation, the formatted information being limited to defects of an appliance chain, the formatted information especially linked to distortions and/or to chromatic aberrations of the appliance chain, wherein the digital image is composed of digital pixels, the transformed image is composed of transformed pixels, and the transformed pixels are characterized by a transformed position and a transformed value, the method comprising:

calculating the transformed image from an approximation of the geometric transformation;

calculating values of the transformed pixels by employing a general algorithm that includes

selecting the transformed pixels, to generate initial transformed pixels,

obtaining blocks of initial digital pixels and initial digital positions by applying the following processes

(a) a process of selecting, within the digital image, from the formatted information, for each transformed position, a block of digital pixels,

(b) a process of calculating, from the formatted information, for each transformed position, a digital position within the block of digital pixels,

(c) a process of calculating, for the transformed position, the value of the transformed pixel as a function of the values of the digital pixels of the block of digital pixels and of the digital position, and

applying an optimized algorithm to each transformed pixel other than the initial transformed pixels, wherein the optimized algorithm includes the following processes

(d) a process of selecting, from the initial digital blocks and/or from each initial transformed position, a block of digital pixels within the digital image,

(e) a process of calculating, from the initial digital blocks and/or from each initial transformed position, a digital position within the block of digital pixels,

(f) a process of calculating the value of the transformed pixel as a function of the values of the digital pixels of the block of digital pixels and of the digital position; and

the formatted information containing parameters, the parameters making it possible to choose at least one mathematical function related to the geometric transformation, the at least one mathematical function making it possible to calculate the block of digital pixels and the digital position from the transformed position.

2. The method according to claim 1, wherein the method is employed with a hardware or a software processor, the optimized algorithm employing exclusively integral or fixed-point data.

3. The method according to claim 1, the method further comprising quantizing the digital positions to obtain quantized digital positions.

4. The method according to claim 3, the method further comprising calculating blocks of coefficients, the processes (c) and (f) being performed by:

using the quantized digital position to select a block of coefficients,

calculating the value of the transformed pixel from the block of coefficients and from the block of digital pixels.

5. The method according to claim 1, wherein the processes (c) and (f) of calculation of the value of the transformed pixel are also applicable to a transformation other than the geometric transformation, and to attenuation of blurring of the image.

6. The method according to claim 1, wherein the digital image is derived from a sensor having a plurality of channels, the channels configured to be combined to produce color planes, the processes (c) and (f) for calculation of the value of the transformed pixel also making it possible to combine the channels to obtain the color planes.

7. The method according to of claim 1, wherein the digital image is composed of color planes, and wherein in the method a different geometric transformation is applied to each color plane to correct chromatic aberrations.

8. The method according to claim 1, the method further comprising combining the geometric transformation with another geometric transformation, especially a zoom effect, that is variable depending on the digital image.

9. The method according to claim 1, wherein the formatted information depends on variable characteristics that depend on the digital image, especially a size of the digital image, the method further comprising:

determining the value of the variable characteristics for the digital image, the processes (a) and (b) using the formatted information depending on the value obtained for the variable characteristics;

wherein employment of the method for the formatted information depending on a variable characteristic reduces to employment of the method for formatted information that does not depend on any variable characteristic.

10. The method according to claim 1, wherein the formatted information is related to distortion defects and/or to chromatic aberrations of the appliance chain, the parameters being related to a measured field.

11. The method according to claim 1, wherein the transformed image exhibits a difference compared with the image obtained by application of the geometric transformation to the digital image, the method further comprising:

choosing a threshold;

choosing the general algorithm and/or the optimized algorithm and/or the initial transformed positions, such that the difference is below the threshold.

12. The method according to claim 3, the transformed image exhibits a difference compared with the image obtained by application of the geometric transformation to the digital image, the method further comprising:

choosing a threshold,

choosing the general algorithm and/or the optimized algorithm and/or the initial transformed positions and/or the quantization of the quantized digital positions, such that the difference is below the threshold.

13. The method according to claim 1, the method further comprising sorting the transformed positions such that the blocks of digital pixels selected by the processes (a) and/or (d) have a specified average number of common digital pixels.

14. A system for calculating a transformed image from a digital image and formatted information related to a geometric transformation, the formatted information being limited to defects of an appliance chain, to distortions and/or to chromatic aberrations of an appliance chain, wherein the digital image is composed of digital pixels, the transformed image is composed of transformed pixels, and the transformed pixels are characterized by a transformed position and a transformed value, the system comprising:

calculating means for calculating the transformed image from an approximation of the geometric transformation,

calculating means for calculating values of the transformed pixels by employing data-processing means provided with a general algorithm, the data-processing means configured

to select the transformed pixels, to generate initial transformed pixels,

to obtain blocks of initial digital pixels and initial digital positions by applying the following processes

(a) a process of selecting, within the digital image, from the formatted information, for each transformed position, a block of digital pixels,

(b) a process of calculating, from the formatted information, for each transformed position, a digital position within the block of digital pixels,

(c) a process of calculating, for the transformed position, the value of the transformed pixel as a function of the values of the digital pixels of the block of digital pixels and of the digital position, and

to apply an optimized algorithm to each transformed pixel other than the initial transformed pixels, wherein the optimized algorithm includes the following processes

(d) a process of selecting, from the initial digital blocks and/or from each initial transformed position, a block of digital pixels within the digital image,

(e) a process of calculating, from the initial digital blocks and/or from each initial transformed position, a digital position within the block of digital pixels,

(f) a process of calculating the value of the transformed pixel as a function of the values of the digital pixels of the block of digital pixels and of the digital position; and

the formatted information containing parameters, the parameters making it possible to choose at least one mathematical function related to the geometric transformation, the at least one mathematical function making it possible to calculate the block of digital pixels and the digital position from the transformed position.

15. The system according to claim 14, wherein the general algorithm or the optimized algorithm is executed by a hardware and/or software processor, the optimized algorithm employing exclusively integral or fixed-point data.

16. The system according to claim 14, wherein the data-processing means quantizes the digital positions to obtain quantized digital positions.

17. The system according to claim 16, the system further comprising calculating means for calculating blocks of coefficients, the processes (c) and (f) being performed by:

using the quantized digital position to select a block of coefficients,

calculating the value of the transformed pixel from the block of coefficients and from the block of digital pixels.

18. The system according to claim 14, wherein the processes (c) and (f) of calculation of the value of the transformed pixel are also applicable to a transformation other than the geometric transformation, and to attenuation of blurring of the image.

19. The system according to claim 14, wherein the digital image is derived from a sensor having a plurality of channels, the channels configured to be combined to produce color planes, the processes (c) and (f) for calculation of the value of the transformed pixel being such that they also make it possible to combine the channels to obtain the color planes.

20. The system according to claim 14, wherein the digital image is composed of color planes, the system being such that the data-processing means is capable of applying a different geometric transformation to each color plane to correct chromatic aberrations.

21. The system according to claim 14, wherein in the system the data-processing means makes it possible to combine the geometric transformation with another geometric transformation, especially a zoom effect, that is variable depending on the digital image.

22. The system according to claim 14, wherein the formatted information depends on variable characteristics that depend on the digital image, especially a size of the digital image, wherein the data-processing means determines the value of the variable characteristics for the digital image, the processes (a) and (b) using the formatted information depending on the value obtained for the variable characteristics.

23. The system according to claim 14, wherein the formatted information is related to distortion defects and/or to chromatic aberrations of the appliance chain, the parameters being related to a measured field.

24. The system according to claim 14, wherein the transformed image exhibits a difference compared with the image obtained by application of the geometric transformation to the digital image, wherein the data-processing means makes it possible to employ the general algorithm and/or the optimized algorithm and/or the initial transformed positions such that the difference is below a chosen threshold.

25. The system according to of claim 16, wherein the transformed image exhibits a difference compared with the image obtained by application of the geometric transformation to the digital image, wherein the data-processing means makes it possible to employ the general algorithm and/or the optimized algorithm and/or the initial transformed positions and/or the quantization of quantized digital positions, such that the difference is below a chosen threshold.

26. The system according to claim 14, wherein the data-processing means sorts the transformed positions such that the blocks of digital pixels selected by the processes (a) and/or (d) have a specified average number of common digital pixels.