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image.pixelvalue - Function

	Package	general
	Module	images
	Tool	image

Get value of image and mask at specified pixel coordinate

Synopsis
pixelvalue(pixel)

Arguments

pixel	in	Pixel coordinate
		Allowed:	Vector of integer
		Default:	Reference pixel

Returns
Glish record, unset, or fail

Description

This function gets the value of the image and the mask at the specified pixel coordinate. The values are returned in a Glish record with fields 'value', 'mask' and 'pixel'. The value is returned as a quantity, the mask as a Bool (T is good). The 'pixel' field holds the actual pixel coordinate used.

If the specified pixel coordinate is off the image, unset is returned.

Excessive elements in pixel are silently discarded. Missing elements are given the (nearest integer) value of the reference pixel. This is reflected in the output record 'pixel' field.

Example

- im := imagemaketestimage();
- im.pixelvalue()
[mask=T, value=[value=2.50643158, unit=Jy/beam], pixel=[56 38] ] 
-
- im.pixelvalue([0,0])
[i_am_unset=i_am_unset] 
-
- im.pixelvalue([10])
[mask=T, value=[value=0.140122071, unit=Jy/beam], pixel=[10 38] ] 
-
- im.pixelvalue([10,10,10])
[mask=T, value=[value=-0.452527285, unit=Jy/beam], pixel=[10 10] ]