gen_radial_distortion_map — Generate a projection map that describes the mapping of images corresponding to a changing radial distortion.
gen_radial_distortion_map computes the mapping of images corresponding to a changing radial distortion in accordance to the internal camera parameters CamParamIn and CamParamOut which can be obtained, e.g., using the operator calibrate_cameras. CamParamIn and CamParamOut contain the old and the new camera parameters including the old and the new radial distortion, respectively (also see write_cam_par for the sequence of the parameters and the underlying camera model). Each pixel of the potential output image is transformed into the image plane using CamParamOut and subsequently projected into a subpixel position of the potential input image using CamParamIn. Note that gen_radial_distortion_map can only be used with area-scan cameras.
The mapping function is stored in the output image Map. The size of Map is given by the camera parameters CamParamOut and therefore defines the size of the resulting mapped images using map_image. The size of the images to be mapped with map_image is determined by the camera parameters CamParamIn. MapType is used to specify the type of the output Map. If 'nearest_neighbor' is chosen, Map consists of one image containing one channel, in which for each pixel of the resulting image the linearized coordinate of the pixel of the input image is stored that is the nearest neighbor to the transformed coordinates. If 'bilinear' interpolation is chosen, Map consists of one image containing five channels. In the first channel for each pixel in the resulting image the linearized coordinates of the pixel in the input image is stored that is in the upper left position relative to the transformed coordinates. The four other channels contain the weights of the four neighboring pixels of the transformed coordinates which are used for the bilinear interpolation, in the following order:
+---+---+ | 2 | 3 | +---+---+ | 4 | 5 | +---+---+
The second channel, for example, contains the weights of the pixels that lie to the upper left relative to the transformed coordinates. If 'coordinate_map_sub_pix' is chosen, Map consists of one vector field image of the semantic type 'vector_field_absolute', in which for each pixel of the resulting image the subpixel precise coordinates in the input image are stored.
If CamParamOut was computed via change_radial_distortion_cam_par, the mapping describes the effect of a lens with a modified radial distortion. If Kappa is 0 , the mapping corresponds to a rectification.
If several images have to be mapped using the same camera parameters, gen_radial_distortion_map in combination with map_image is much more efficient than the operator change_radial_distortion_image because the transformation must be computed only once.
If you want to re-use the created map in another program, you can save it as a multi-channel image with the operator write_image, using the format 'tiff'.
Image containing the mapping data.
Old camera parameters.
Number of elements: (CamParamIn == 8) || (CamParamIn == 12)
New camera parameters.
Number of elements: (CamParamOut == 8) || (CamParamOut == 12)
Type of the mapping.
Default value: 'bilinear'
List of values: 'nearest_neighbor', 'bilinear', 'coord_map_sub_pix'
gen_radial_distortion_map returns 2 (H_MSG_TRUE) if all parameter values are correct. If necessary, an exception is raised.
change_radial_distortion_cam_par, camera_calibration, hand_eye_calibration