Operator Reference
gen_arbitrary_distortion_map (Operator)
gen_arbitrary_distortion_map — Generate a projection map that describes the mapping between an arbitrarily
distorted image and the rectified image.
Signature
gen_arbitrary_distortion_map( : Map : GridSpacing, Row, Column, GridWidth, ImageWidth, ImageHeight, MapType : )
Description
gen_arbitrary_distortion_map computes the mapping Map
between an arbitrarily distorted image and the rectified image.
The coordinates Row and Column describe a distorted grid,
which will be mapped onto a regular grid in the rectified image.
The coordinates of the (distorted) grid points must be passed line by line
in Row and Column. GridWidth is the width of the
point grid in grid points. GridSpacing is the distance between
two adjacent grid points in the rectified image. Because the grid points
are always mapped to the centers of their corresponding pixels a grid cell
requires (GridSpacing+1) x (GridSpacing+1) pixels in the
rectified image. Note however, that, of course, adjacent grid cells
overlap by one pixel.
To compute the mapping Map, additionally the width
ImageWidth and height ImageHeight of the images to be
rectified must be passed.
MapType is used to specify the type of the output Map.
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 'coord_map_sub_pix' is chosen, Map consists of
one vector field image, in which for each pixel of the resulting image
the subpixel precise coordinates in the input image are stored.
As mentioned above, four adjacent pixels in the distorted image are required
to interpolate the gray value of one pixel in the mapped image. If at
least one of these pixels is located outside of the distorted image the
gray value can not be calculated. The domain of the resulting Map
domain is reduced accordingly.
In contrary to gen_grid_rectification_map,
gen_arbitrary_distortion_map is used when the coordinates
(Row,Column) of the grid points in the distorted image are
already known or the relevant part of the image consist of regular grid
structures, which the coordinates can be derived from.
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'.
Execution Information
- Multithreading type: reentrant (runs in parallel with non-exclusive operators).
- Multithreading scope: global (may be called from any thread).
- Processed without parallelization.
Parameters
Map (output_object) multichannel-image → object (int4 / uint2 / vector_field)
Image containing the mapping data.
GridSpacing (input_control) integer → (integer)
Distance of the grid points in the rectified image.
Restriction:
GridSpacing > 0
Row (input_control) point.y-array → (real)
Row coordinates of the grid points in the distorted image.
Column (input_control) point.x-array → (real)
Column coordinates of the grid points in the distorted image.
Restriction:
number(Row) == number(Column)
GridWidth (input_control) integer → (integer)
Width of the point grid (number of grid points).
ImageWidth (input_control) extent.x → (integer)
Width of the images to be rectified.
Restriction:
ImageWidth > 0
ImageHeight (input_control) extent.y → (integer)
Height of the images to be rectified.
Restriction:
ImageHeight > 0
MapType (input_control) string → (string)
Type of mapping.
Default: 'bilinear'
List of values: 'bilinear', 'coord_map_sub_pix'
Result
gen_arbitrary_distortion_map returns 2 (
H_MSG_TRUE)
if all parameter values
are correct. If necessary, an exception is raised.
Possible Successors
See also
create_rectification_grid,
find_rectification_grid,
connect_grid_points,
gen_grid_rectification_map
Module
Calibration