Operator Reference
get_grayval_contour_xld (Operator)
get_grayval_contour_xld — Return gray values of an image at the positions of an XLD contour.
Signature
get_grayval_contour_xld(Image, Contour : : Interpolation : Grayval)
Description
The operator get_grayval_contour_xld returns interpolated
gray values at several subpixel positions of the Image.
The coordinates of the positions are specified via one XLD contour
Contour. The gray values are returned in Grayval.
The interpolation method can be selected via the parameter
Interpolation:
- 'nearest_neighbor':
-
The results are the gray values of the nearest pixels to the selected coordinates. For images of type byte, direction, cyclic, uint2, int1, int2, int4, and int8, the parameter
Grayvalis a tuple of integer numbers. For images of type real and complex, the parameterGrayvalis a tuple of floating point numbers. - 'bilinear':
-
The parameter
Grayvalis computed using a bilinear interpolation of the four neighboring gray values of the selected coordinates. The result is a tuple of floating point numbers. The runtime increases significantly compared to 'nearest_neighbor'. Direction and cyclic images are treated like byte images. - 'bicubic':
-
The parameter
Grayvalis computed using a bicubic interpolation of sixteen neighboring gray values of the selected coordinates. The result is a tuple of floating point numbers. The runtime increases significantly compared to 'bilinear'. Direction and cyclic images are treated like byte images. In this mode, the resulting gray values may contain values that lie outside of the range of numbers that can be represented by the input image type. - 'bicubic_clipped':
-
The parameter
Grayvalis computed using a bicubic interpolation of sixteen neighboring gray values of the selected coordinates. The result is a tuple of floating point numbers. The runtime increases significantly compared to 'bilinear'. Direction and cyclic images are treated like byte images. In this mode, resulting gray values that lie outside of the range of numbers that can be represented by the input image type are clipped to that range.
Note that get_grayval_contour_xld does not take the domain of
the image into account, i.e., if the domain has been reduced, e.g.,
with reduce_domain, gray values are returned even for points
that lie outside the domain.
Please note also that each point of the XLD contour must be in the
range -0.5 <= row coordinate <
height(Image)-0.5 and -0.5 <= column
coordinate < width(Image)-0.5.
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
Image (input_object) singlechannelimage → object (byte / direction / cyclic / int1 / int2 / uint2 / int4 / real / complex)
Image whose gray values are to be accessed.
Contour (input_object) xld_cont → object
Input XLD contour with the coordinates of the positions.
Interpolation (input_control) string → (string)
Interpolation method.
Default: 'nearest_neighbor'
List of values: 'bicubic', 'bicubic_clipped', 'bilinear', 'nearest_neighbor'
Grayval (output_control) grayval(-array) → (real / integer)
Gray values of the selected image coordinates.
Result
If the parameters are valid, the operator
get_grayval_contour_xld returns the value 2 (
H_MSG_TRUE)
. If
necessary, an exception is raised.
Possible Predecessors
read_image,
draw_xld,
gen_contour_polygon_xld,
edges_sub_pix
Alternatives
Module
Foundation