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image.getregion - Function

1.1.1 Get pixels or mask from a region-of-interest of the image


Description

This function recovers the image pixel or pixel mask values in the given region-of-interest. Regardless of the shape of the region you have specified, the shape of the pixels and pixelmask arrays must necessarily be the bounding box of the specified region. If the region extends beyond the image, it is truncated.

Recall that the recovered pixel mask will reflect both the pixel mask stored in the image, and the region-of-interest (their masks are ‘anded’) – see the discussion in the introduction about this.

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.

This function differs in three ways from getchunk. First, the region can be much more complex (e.g. a union of polygons) than the simple blc, trc, and inc of getchunk (although such a region can be created of course). Second, it can be used to recover the pixel mask or the pixels. Third, it is less efficient than getchunk for doing the same thing as getchunk. So if you are interested in say, iterating through an image, getting a regular hyper-cube of pixels and doing something with them, then getchunk will be faster. This would be especially noticeable if you iterated line by line through a large image.

Arguments





Inputs

region

Region selection. See ”help par.region” for details. Default is to use the full image.

allowed:

any

Default:

variant

axes

Axes to average over. Default is none.

allowed:

intArray

Default:

-1

mask

Mask to use. See help par.mask. Default is none.

allowed:

variant

Default:

list

List the bounding box to the logger

allowed:

bool

Default:

false

dropdeg

Drop degenerate axes

allowed:

bool

Default:

false

getmask

Get the pixel mask rather than pixel values

allowed:

bool

Default:

false

stretch

Stretch the mask if necessary and possible? See help par.stretch. Default False

allowed:

bool

Default:

false

Returns
variant

Example

 
Suppose that we have a 3-dimensional image called {\sff cube} and wish  
to recover the pixel from a simple regular region.  
 
"""  
#  
print "\t----\t getregion Ex 1 \t----"  
ia.fromshape(’cube’, [64,64,64], overwrite=true)  
#r1=rg.box(blc=[10,10,10],trc=[30,40]) # Create region  
r1=rg.box([10,10,10],[30,40,40]) # Create region  
pixels=ia.getregion(r1)  
ia.close()  
#  
"""  
 

Example

 
 
"""  
#  
print "\t----\t getregion Ex 2 \t----"  
ia.fromshape(’cube’, [64,64,64], overwrite=true)  
pixels = ia.getregion()  
pixelmask = ia.getregion(getmask=T)  
#  
"""  
 
In this example we recover first the pixels and then the pixel mask.  

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