Operator Reference
get_grayval (Operator)
get_grayval — Access the gray values of an image object.
Signature
Description
The parameter Grayval is a tuple of floating point numbers
or integer numbers which returns the gray values of several pixels
of Image. For a multi-channel image, a group of elements,
in particular one value for each channel (or two values for each
channel for complex or vector field images), is returned for each
pixel. The row coordinates of the pixels are specified in the tuple
Row, the column coordinates are specified in the tuple
Column.
Note that get_grayval 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.
Attention
The type of the values of Grayval depends on the type of
the gray values of the channels of the image Image. The
operator get_grayval produces quite some overhead.
Typically, it is used to get single gray values of an image (e.g.,
get_mposition followed by get_grayval). It is not
suitable for programming image processing operations such as
filters. In this case it is more useful to use the operator
get_image_pointer1 and to directly use the C or C++
interface for integrating own procedures.
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) (multichannel-)image → object (byte / direction / cyclic / int1 / int2 / uint2 / int4 / int8 / real / complex / vector_field)
Image whose gray value is to be accessed.
Row (input_control) point.y(-array) → (integer)
Row coordinates of pixels to be viewed.
Default: 0
Suggested values: 0, 64, 128, 256, 512, 1024
Value range:
0
≤
Row
≤
32767 (lin)
Minimum increment: 1
Recommended increment: 1
Restriction:
0 <= Row && Row < height(Image)
Column (input_control) point.x(-array) → (integer)
Column coordinates of pixels to be viewed.
Number of elements: Column == Row
Default: 0
Suggested values: 0, 64, 128, 256, 512, 1024
Value range:
0
≤
Column
≤
32767 (lin)
Minimum increment: 1
Recommended increment: 1
Restriction:
0 <= Column && Column < width(Image)
Grayval (output_control) grayval-array → (real / integer)
Gray values of indicated pixels.
Result
If the state of the parameters is correct, the operator
get_grayval returns the value 2 (
H_MSG_TRUE)
. The behavior in case of
empty input (no input images available) is set via the operator
set_system('no_object_result',<Result>). If necessary, an
exception is raised.
Possible Predecessors
Alternatives
get_image_pointer1,
get_grayval_interpolated,
get_grayval_contour_xld
See also
Module
Foundation