1.1.1.0 image.getchunk

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image.getchunk - Function

1.1.1 Get the pixel values from a regular region of the image into an array

Description

This function returns the pixels (or optionally the pixel mask) from the image file between blc and trc inclusively. Both float and complex valued images are supported. An increment may be specified with inc. Note that if you retrieve too many pixels, you might cause swapping since the pixels are kept in memory.

Any illegal blc values are set to zero. Any illegal trc values are set to the end of the image. If any trc < blc, you get the whole image for that axis. Any illegal inc values are set to unity.

The argument axes can be used to reduce the dimensionality of the output array. It specifies which pixel axes of the image to average the data over. For example, consider a 3-D image. With axes=[0,1] and all other arguments left at their defaults, the result would be a 1-D vector, a profile along the third axis, with the data averaged over the first two axes.

A related function is getregion which retrieves the pixels or pixel mask from a potentially more complex region-of-interest. Function getchunk is retained because it is faster and therefore preferable for repeated operation in loops if the pixel mask is not required and the region is a simple box.

If you set getmask=True, the return value is the ’pixelmask’ rather than the ’pixel’ image.

Arguments


Inputs
blc	Bottom-Left-Corner (beginning) of pixel section. Default is start of image.
	allowed:	intArray
	Default:	-1
trc	Top-Right-Corner (end) of pixel section. Default is end of image.
	allowed:	intArray
	Default:	-1
inc	increment (stride) along axes
	allowed:	intArray
	Default:	1
axes	Axes to average over. Default is none.
	allowed:	intArray
	Default:	-1
list	List bounding box to logger?
	allowed:	bool
	Default:	false
dropdeg	Drop degenerate axes?
	allowed:	bool
	Default:	false
getmask	Get the pixel mask rather than the pixel values
	allowed:	bool
	Default:	false

Returns
anyvariant

Example

Suppose that we have a 3-dimensional image called {\sff im}. Then:

"""
#
print "\t----\t getchunk Ex 1 \t----"
ia.fromshape(shape=[64,64,128])
pix = ia.getchunk()                      # all pixels
ia.calcmask(’T’)                         # give image a mask
pix = ia.getchunk([1,1,1], [10,10,1])    # 10 by 10 section of plane # 1
pix = ia.getchunk([1,1], [1,1])          # first spectrum
pix = ia.getchunk(inc=[1,5])             # all planes, decimated by 5 in y
mask = ia.getchunk(getmask=True)            # Get pixelmask
ia.close()
#
"""

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