DOCHighLevel_utils

#Utility Classes

The idea of this document is to show how to create a utility type class in chimera.

##Introduction

We describe how to write a utility using chimera framework.

• This kind of program does not need chimera objects.

• It does not need the chimera daemon to be running.

• It is basically like any other python class.

However, it does use chimera classes and is written to be used by other chimera objects, particularly while chimera is running.

I show here the implementation of the astrometrynet class used to call solve-field (from astrometry.net) to find the WCS for a given image.

##Details

from subprocess import Popen
from chimera.util.sextractor import SExtractor
from chimera.core.exceptions import ChimeraException
from chimera.util.image import Image

import os
import shutil
from pyraf import iraf

import logging
import chimera.core.log
log = logging.getLogger(__name__)

• Note some of these are chimera classes, some are standard python classes.
• The astrometrynet class starts down here. The goal is to run the solve-field program from astrometrynet (as a system call) on a given image and to create a copy of the original image with a modified header reflecting the WCS found by solve-field:

class AstrometryNet:
    
    # staticmethod allows to use a single method of a class
    @staticmethod
    def solveField(fullfilename, findstarmethod="astrometry.net"):
        """
        @param: fullfilename entire path to image
        @type: str

        @param: findstarmethod (astrometry.net, sex) 
        @type: str

        Does astrometry to image=fullfilename
        Uses either astrometry.net or sex(tractor) as its star finder

        """

        pathname, filename = os.path.split(fullfilename)
        pathname = pathname + "/"
        basefilename,file_xtn = os.path.splitext(filename)
        # *** enforce .fits extension
        if (file_xtn != ".fits"):
            raise ValueError("File extension must be .fits it was = %s\n" %file_xtn)

        # *** check whether the file exists or not
        if ( os.path.exists(fullfilename) == False ):
            raise IOError("You selected image %s  It does not exist\n" %fullfilename)

        # version 0.23 changed behavior of --overwrite
        # I need to specify an output filename with -o
        outfilename = basefilename + "-out"

• Here I use a chimera class for the first time. I am using the image class : *

        image = Image.fromFile(fullfilename)
        try:
            ra = image["CRVAL1"]    # expects to see this in image
        except:
            raise AstrometryNetException("Need CRVAL1 and CRVAL2 and CD1_1 on header")
        try:
            dec = image["CRVAL2"]
        except:
            raise AstrometryNetException("Need CRVAL1 and CRVAL2 and CD1_1 on header")
        width = image["NAXIS1"]
        height = image["NAXIS2"] 
        radius = 5.0 * abs(image["CD1_1"]) * width

• Now, I ask whether I am using astrometrynet internal star finder or sextractor. I build a command line to run solve-field based on this information:

        if findstarmethod == "astrometry.net":
            #line = "solve-field --guess-scale %s --overwrite -o %s" %(fullfilename, outfilename)
            line = "solve-field %s --overwrite -o %s --ra %f --dec %f --radius %f"  %(fullfilename, outfilename, ra, dec, radius)
            print line

        elif findstarmethod == "sex":
            sexoutfilename = pathname + outfilename + ".xyls"
            line = "solve-field %s --overwrite -o %s --x-column X_IMAGE --y-column Y_IMAGE --sort-column MAG_ISO --sort-ascending --width %d --height %d --ra %f --dec %f --radius %f"  %(sexoutfilename, outfilename, width, height, ra, dec, radius)
            print "Sextractor command line %s" %line
            # using --guess-scale
            # line = "solve-field %s --overwrite -o %s --x-column X_IMAGE --y-column Y_IMAGE --sort-column MAG_ISO --sort-ascending --width %d --height %d --guess-scale"  %(sexoutfilename, outfilename, width, height)

            sex = SExtractor()
            sex.config['BACK_TYPE']   = "AUTO"
            sex.config['DETECT_THRESH'] = 3.0
            sex.config['DETECT_MINAREA'] = 18.0
            sex.config['VERBOSE_TYPE'] = "QUIET"
            sex.config['CATALOG_TYPE'] = "FITS_1.0"
            #sex.config['CATALOG_TYPE'] = "ASCII"
            sex.config['CATALOG_NAME'] = sexoutfilename
            sex.config['PARAMETERS_LIST'] = ["X_IMAGE","Y_IMAGE","MAG_ISO"]
            sex.run(fullfilename)

        else:
            log.error("Unknown option used in astrometry.net")

• check to see if astrometry.net found a solution:

        # when there is a solution astrometry.net creates a file with .solved
        # added as extension.  
        is_solved = pathname + outfilename + ".solved"
        # if it is already there, make sure to delete it 
        if ( os.path.exists(is_solved)):
            os.remove(is_solved)
	print "SOLVE"  , line
        solve = Popen(line.split()) # ,env=os.environ)
        solve.wait()
        # if solution failed, there will be no file .solved
        if ( os.path.exists(is_solved) == False ):
            raise NoSolutionAstrometryNetException("Astrometry.net could not find a solution for image: %s %s" %(fullfilename, is_solved))

        # wcs_imgname will be the old fits file with the new header
        # wcs_solution is the solve-field solution file
        wcs_imgname = pathname + outfilename + "-wcs" + ".fits"
        wcs_solution = pathname + outfilename + ".wcs"
        shutil.copyfile(wcs_solution,wcs_solution+".fits")
        if ( os.path.exists(wcs_imgname) == True ):
            iraf.imdelete(wcs_imgname)

        # create a separate image with new header
        iraf.artdata()
        iraf.imcopy(fullfilename,wcs_imgname)
        iraf.mkheader(images=wcs_imgname,headers=wcs_solution+".fits",
                      append="no",verbose="no",mode="al")
        return(wcs_imgname)

##Exceptions

class AstrometryNetException(ChimeraException):
    pass        

class NoSolutionAstrometryNetException(ChimeraException):
    pass