get_greyval__ ( Image : : Row, Column : Greyval )

Access the gray values of an image object.

The operator Greyval is a tuple of floating point numbers orintegers, respectively, which returns the gray values of several pixels of Image. The line coordinates of the pixels are in the tuple Row, the columns in Column.


Attention

The type of the values of Greyval depends on the type of the gray values.

Gray values which do not belong to the image can also be accessed; the state of these gray values is not ascertained.

The operator get_greyval__ involves a lot of work. It is not suitable for programming image processing operations such as filters. In this case it is more useful to use the procedure get_image_pointer__ or to directly use the C interface for integrating own procedures.


Parameters

Image (input_object)
image -> object
Image whose gray value is to be accessed.

Row (input_control)
point.y(-array) -> integer
Line numbers of pixels to be viewed.
Default value: 0
Suggested values: 0, 64, 128, 256
Range of values: 0 <= Row <= 511 (lin)
Minimum increment: 1
Recommended increment: 1

Column (input_control)
point.x(-array) -> integer
Column numbers of pixels to be viewed.
Default value: 0
Suggested values: 0, 64, 128, 256
Range of values: 0 <= Column <= 511 (lin)
Minimum increment: 1
Recommended increment: 1
Number of elements: Column == Row

Greyval (output_control)
greyval(-array) -> real / integer
Gray values of indicated pixels.
Number of elements: Greyval == Row


Result

If the state of the parameters is correct the operator get_greyval__ returns the value 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

read_image, read_picture


Alternatives

get_image_pointer__


See also

set_greyval__



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