Apparatus and a method for obtaining a registration error map representing a level of sharpness of an image
The present invention generally relates to an apparatus and a method for obtaining a registration error map representing a level of sharpness of an image. Many methods are known which allow determining the position of a camera with respect to an object, based on the knowledge of a 3D model of the object and the intrinsic parameters of the camera. However, regardless of the visual servoing technique used, there is no control in the image space and the object may get out of the camera field of view during servoing. It is proposed to obtain a registration error map relating to an image of the object of interest generated by computing an intersection of a re-focusing surface obtained from a 3D model of said object of interest and a focal stack based on acquired four-dimensional light-field data relating to said object of interest.
1. An apparatus comprising:
a processor configured to:
receiving an image having an object of interest;
obtaining a registration error map relating to the image of the object of interest generated by determining a refocusing surface obtained from a distance map of a three-dimensional model of said object of interest when set in a reference position and a focal stack generated from acquired four-dimensional light-field data relating to said object of interest; and
generating a map representing a level of sharpness of at least a plurality of pixels in said image using said registration error map.
2. The apparatus according to claim 1 wherein the processor is configured to compute an intersection of the refocusing surface and the focal stack by determining for each pixel of the image to be re-focused a re-focusing distance corresponding to one of the images constituting the focal stack from the predefined refocusing surface.
3. The apparatus according claim 2 , wherein the processor is configured to generate an appearance of the registration error map to be displayed based on information relating to a level of sharpness of the pixels of the re-focused image.
4. The apparatus according to claim 1 , wherein the processor is configured to display the obtained registration error map on a display device of the apparatus.
5. A method comprising:
receiving an image having an object of interest;
obtaining a registration error map relating to the image of the object of interest generated by determining a refocusing surface obtained from a distance map of a three-dimensional model of said object of interest when set in a reference position and a focal stack generated from acquired four-dimensional light-field data relating to said object of interest; and
generating a map representing a level of sharpness of at least a plurality of pixels in said image using said registration error map.
6. The method according to claim 5 wherein determining an intersection of the distance map and the focal stack comprises determining for each pixel of the image to be re-focused a re-focusing distance corresponding to one of the images constituting the focal stack from the re-focusing-surface.
7. The method according to claim 6 further comprising generating an appearance of the registration error map to be displayed based on information relating to a level of sharpness of the pixels of the re-focused image.
8. The method according to any one of claim 7 comprising displaying the obtained registration error map on a display device.
9. A computer program characterized in that it comprises program code instructions for the implementation of the method for obtaining a registration error map representing a level of sharpness of an image according to claim 5 when the program is executed by a processor.
10. A processor readable medium having stored therein instructions for causing a processor to perform the method for obtaining a registration error map representing a level of sharpness of an image according to claim 5 .
11. Non-transitory storage medium carrying instructions of program code for executing the method for obtaining a registration error map representing a level of sharpness of an image according to claim 5 , when said program is executed on a determining device,
shifting the point of view of said four-dimensional light-field data relating to said object of interest until the pixels of an image of an object of interest are sharp.