6 Image Analysis

NRAO Home > CASA > CASA Cookbook and User Reference Manual

Chapter 6
Image Analysis

Inside the Toolkit:

Image analysis is handled in the ia tool. Many functions exist there, including region statistics and image math. See § 6.17 below for more information.

Once data has been calibrated (and imaged in the case of synthesis data), the resulting image or image cube must be displayed or analyzed in order to extract quantitative information, such as statistics or moment images. In addition, there need to be facilities for the coordinate conversion of images for direct comparison.

The image analysis tasks are:

imhead — summarize and manipulate the “header” information in a CASA image (§ 6.2)
imcontsub — perform continuum subtraction on a spectral-line image cube (§ 6.3)
imfit — image plane Gaussian component fitting (§ 6.4)
immath — perform mathematical operations on or between images (§ 6.5)
immoments — compute the moments of an image cube (§ 6.6)
imstat — calculate statistics on an image or part of an image (§ 6.7)
imval — extract the data and mask values from a pixel or region of an image (§ 6.8)
imtrans — reorder the axes of an image or cube (§ 6.9)
imcollapse — collapse image along one or more axes by aggregating pixel values along that axis (§ 6.10)
imregrid — regrid an image onto the coordinate system of another image (§ 6.11)
imsmooth — smooth images in the spectral and angular directions (§ 6.12)
specfit — fit 1-dimensional Gaussians, polynomial, and/or Lorentzians models to an image or image region (§ 6.13)
slsearch — query a subset of the Splatalogue spectral line catalog (§ 6.14)
splattotable — convert a file exported from Splatalogue to a CASA table (§ 6.15)
importfits — import a FITS image into a CASA image format table (§ 6.16.2)
exportfits — write out an image in FITS format (§ 6.16.1)

There are other tasks which are useful during image analysis. These include:

viewer — there are useful region statistics and image cube slice and profile capabilities in the viewer (§ 7)

We also give some examples of using the CASA Toolkit to aid in image analysis (§ 6.17).

6.1 Common Image Analysis Task Parameters
  6.1.1 Region Selection (box)
  6.1.2 Plane Selection (chans, stokes)
  6.1.3 Lattice Expressions (expr)
  6.1.4 Masks (mask)
  6.1.5 Regions (region)
6.2 Image Header Manipulation (imhead)
  6.2.1 Examples for imhead
6.3 Continuum Subtraction on an Image Cube (imcontsub)
  6.3.1 Examples for imcontsub)
6.4 Image-plane Component Fitting (imfit)
  6.4.1 Examples for imfit
6.5 Mathematical Operations on an Image (immath)
  6.5.1 Examples for immath
  6.5.2 Using masks in immath
6.6 Computing the Moments of an Image Cube (immoments)
  6.6.1 Hints for using (immoments)
  6.6.2 Examples using (immoments)
6.7 Computing image statistics (imstat)
  6.7.1 Using the task return value
  6.7.2 Examples for imstat
6.8 Extracting data from an image (imval)
6.9 Reordering the Axes of an Image Cube (imtrans)
6.10 Collapsing an Image Along an Axis (imcollapse)
6.11 Regridding an Image (imregrid)
6.12 Image Convolution(imsmooth)
6.13 Spectral Line fitting with specfit
  6.13.1 Polynomial Fits
  6.13.2 Lorentzian and Gaussian Fits
  6.13.3 Pixel-by-pixel fits
6.14 Search for Spectral Line Rest Frequencies (slsearch)
6.15 Convert Exported Splatalogue Catalogs to CASA Tables (splattotable)
6.16 Image Import/Export to FITS
  6.16.1 FITS Image Export (exportfits)
  6.16.2 FITS Image Import (importfits)
6.17 Using the CASA Toolkit for Image Analysis
6.18 Examples of CASA Image Analysis

[next] [prev] [prev-tail] [front] [up]

More information about CASA may be found at the CASA web page

This code is available under the terms of the GNU General Public Lincense

Chapter 6Image Analysis

Chapter 6
Image Analysis