Getting Started

Documentation

Glish

Learn More

Programming

Contact Us

Version 1.9 Build 1488

News	FAQ
Search	Home

regionmanager.wpolygon - Function

	Package	general
	Module	images
	Tool	regionmanager

Create a world polygon region with quantities

Synopsis
wpolygon(x, y, pixelaxes, csys, absrel, comment)

Arguments

x	in	The x vector
		Allowed:	Quantity vector
y	in	The y vector
		Allowed:	Quantity vector
pixelaxes	in	which pixel axes
		Allowed:	Vector of integers or strings
		Default:	[1,2]
csys	in	Coordinate System
		Allowed:	coordinates tool
		Default:	Privaet Coordinate System
absrel	in	Absolute or relative coordinates
		Allowed:	String from 'abs', 'relref' and 'relcen'
		Default:	'abs'
comment	in	A comment stored with the region
		Allowed:	String

Returns
Region tool

Description

This function (short-hand name wpoly) creates a 2D world polygon region. The polygon is specified by an x and a y vector. These must be quantities of a vector (the world box function allows both quantities of vectors and vectors of quantities). This means that the units are common to all elements of each vector. Thus, dq.quantity([1,2,3],'rad') (a quantity of a vector) is different from dq.quantity("1rad 2rad 3rad") (a vector of quantities) although the information that they specify is the same.

You specify which pixel axes in the image the x and y vectors pertain to with the pixelaxes argument. If you don't, it defaults to [1,2]. This specification is an important part of world regions.

You can specify whether the x and y vector coordinates are given as absolute coordinates (absrel='abs') or relative to the reference pixel (absrel='relref') or relative to the center of the image (absrel='relcen'). This argument applies to both the axes of the polygon.

You must also specify the Coordinate System with the csys argument. The Coordinate System is encapsulated in a coordinates tool and can be recovered from an image with the coordsys function. You can also set a default Coordinate System in the Regionmanager with the setcoordinates function.

In the Regionmanager we have defined units `pix' and `frac'; these are then known to the quanta system. This means that you can effectively define a pixel box (except for the stride capability) as a world box with most of the advantages of world regions (can be used for compound regions). However, it is still not very portable to other images because the coordinates are pixel based, not world based.

Note that the need to deal with the pixelaxes and csys is hidden from you when using the gui interface of the Regionmanager.

Example

- im := image('onno')
- cs := im.coordsys()
- im.shape()
[155 178 64]  
- x := dq.quantity([3,6,9,6,5,5,3],'pix')
- y := dq.quantity([3,4,7,9,7,5,5],'pix')
- r1 := drm.wpolygon(x=x, y=y, pixelaxes=[2,3], csys=cs)
- im.statistics(region=r1)
Selected bounding box [1, 3, 3] to [155, 9, 9]
Creating new statistics storage image

Number points = 3875           
Sum           = -9.457746e+01         Mean     = -2.440709e-02  
Variance      = 2.599452e-02          Sigma    = 1.612282e-01   
Rms           = 1.630445e-01   

Minimum value at [50, 7, 5] = -6.885301e-01  
Maximum value at [155, 3, 5] = 6.562161e-01

We applied the 2D polygon, defined in the YZ plane with absolute pixel coordinates, to a 3D image. Therefore, the first (X) axis was automatically extended to the whole image.