Operator Reference
get_grayval_interpolated (Operator)
get_grayval_interpolated — Return gray values of an image at the positions given by tuples of
rows and columns.
Signature
get_grayval_interpolated(Image : : Row, Column, Interpolation : Grayval)
Description
The operator get_grayval_interpolated returns interpolated
gray values at several subpixel positions of an Image. The
coordinates of the row positions are given in the tuple
Row, the coordinates of column positions are given in the
tuple Column. The gray values are returned in
Grayval as a tuple of floating point numbers.
The interpolation method can be selected via the parameter
Interpolation. The following interpolation methods are
supported:
- 'bilinear':
-
The parameter
Grayvalis computed using a bilinear interpolation of the four neighboring gray values of the selected coordinates. Note: 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. 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. 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_interpolated 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.
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.
Row (input_control) point.y(-array) → (real / integer)
Row coordinates of positions.
Default: 0
Suggested values: 0, 64, 128, 256, 512, 1024
Value range:
-0.5
≤
Row
Restriction:
-0.5 <= Row && Row < height(Image) - 0.5
Column (input_control) point.x(-array) → (real / integer)
Column coordinates of positions.
Number of elements: Column == Row
Default: 0
Suggested values: 0, 64, 128, 256, 512, 1024
Value range:
-0.5
≤
Column
Restriction:
-0.5 <= Column && Column < width(Image) - 0.5
Interpolation (input_control) string → (string)
Interpolation method.
Default: 'bilinear'
List of values: 'bicubic', 'bicubic_clipped', 'bilinear'
Grayval (output_control) grayval(-array) → (real)
Gray values of the selected image coordinates.
Result
If the parameters are valid, the operator
get_grayval_interpolated returns the value 2 (
H_MSG_TRUE)
. If
necessary, an exception is raised.
Possible Predecessors
Alternatives
get_grayval_contour_xld,
get_grayval
Module
Foundation