How to use the tractor.sdss.get_tractor_image function in tractor

itune2 = 5
    ntune = 0
    IRLS_scale = 25.

    bands=['r','g','u','i','z']
    bandname = 'r'
    flipBands = ['r']

    rerun = 0

    TI = []
    sources = []
    for rcf in rcfs:
        print rcf
        try:
            TI.extend([st.get_tractor_image(rcf[0], rcf[1], rcf[2], bandname,useMags=True) for bandname in bands])
            sources.append(st.get_tractor_sources(rcf[0], rcf[1], rcf[2],bandname,bands=bands))
        except:
            print "Sources not in data! %s" % (rcf)

    timg,info = TI[0]
    photocal = timg.getPhotoCal()

    wcs = timg.getWcs()
    lvl = logging.DEBUG
    logging.basicConfig(level=lvl,format='%(message)s',stream=sys.stdout)

    tims = [timg for timg,tinf in TI]
    tractor = st.SDSSTractor(tims)
    for source in sources:
        tractor.addSources(source)

for theta in np.linspace(0,2*np.pi,100):
        ux = np.cos(theta)
        uy = np.sin(theta)
        x.append(ux*radius+x0)
        y.append(uy*radius+y0)

    plt.plot(x,y)
    plt.plot(x0,y0,'o')



#    colors = ['r','g','y','b','k','m','c']

#    for col,rcf in zip(colors,rcfs):
    for rcf in rcfs:
        timg,info = st.get_tractor_image(rcf[0],rcf[1],rcf[2],bandname,useMags=True)
        wcs = timg.getWcs()
        rd = wcs.pixelToPosition(0,0)
        rd2 = wcs.pixelToPosition(width,height)
        print(rd)
        print(rd2)

        plt.plot((rd.ra,rd.ra,rd2.ra,rd2.ra,rd.ra),(rd.dec,rd2.dec,rd2.dec,rd.dec,rd.dec))
        plt.text((rd.ra+rd2.ra)/2.,(rd.dec+rd2.dec)/2.,"Run: %s, Camcol: %s, Field: %s" % (rcf[0],rcf[1],rcf[2]),fontsize=10.,va='center',ha='center')

    #    plt.plot(rd.ra,rd.dec,'+',color=col)
    #    plt.plot(rd2.ra,rd.dec,'+',color=col)
    #    plt.plot(rd.ra,rd2.dec,'+',color=col)
    #    plt.plot(rd2.ra,rd2.dec,'+',color=col)


    print("Saving figure")

y0 = 400
    y1 = 850
    starx = 200. #Star location
    stary = 300.
    starr = 50. #Star radius

    roi = [x0,x1,y0,y1]
    
    bands=['r','g','i','u','z']
    bandname = 'r'
    flipBands = ['r']

    rerun = 0

    TI = []
    TI.extend([st.get_tractor_image(run, camcol, field, bandname,roi=roi,useMags=True) for bandname in bands])
    sources = st.get_tractor_sources(run, camcol, field,bandname, bands=bands,roi=roi)

    timg,info = TI[0]
    photocal = timg.getPhotoCal()

    wcs = timg.getWcs()
    lvl = logging.DEBUG
    logging.basicConfig(level=lvl,format='%(message)s',stream=sys.stdout)

    tims = [timg for timg,tinf in TI]
    tractor = st.SDSSTractor(tims)
    tractor.addSources(sources)

    zr = np.array([-5.,+5.]) * info['skysig']

    print(bands)

ra = 198.05
    dec = 44.0333
    itune = 5
    ntune = 2

    bands=['r','g','u','i','z']
    bandname = 'r'
    flipBands = ['r']

    rerun = 0

    TI = []
    sources = []
    for run,field,camcol,roi in zip(run,field,camcol,roi):
        TI.extend([st.get_tractor_image(run, camcol, field, bandname,useMags=True,roi=roi) for bandname in bands])
        sources.append(st.get_tractor_sources(run, camcol, field,bandname,bands=bands,roi=roi))

    timg,info = TI[0]
    photocal = timg.getPhotoCal()

    wcs = timg.getWcs()
    lvl = logging.DEBUG
    logging.basicConfig(level=lvl,format='%(message)s',stream=sys.stdout)

    tims = [timg for timg,tinf in TI]
    tractor = st.SDSSTractor(tims)
    for source in sources:
        tractor.addSources(source)

    zr = np.array([-5.,+5.]) * info['skysig']

print('Filtering out run 206:', len(rcf))

	sdss = DR7()
	sdss.setBasedir('faint')
	band = 'z'
	skies = []
	ims = []
	tais = []
	rcfs = []
	#S = 50
	S = 40
	for i,(r,c,f,ra,dec) in enumerate(rcf):
		print()
		print('Retrieving', (i+1), 'of', len(rcf), r,c,f,band)
		try:
			im,info = st.get_tractor_image(r, c, f, band, psf='dg', useMags=True,
										   sdssobj=sdss,
										   roiradecsize=(RA, DEC, S/2))
		except:
			continue
		skies.append((info['sky'], info['skysig']))
		tais.append(info['tai'])
		rcfs.append((r,c,f))
		ims.append(im)

		### 
		#if i == 9:
		#	break
			
	return ims,skies,tais,rcfs

# def getModelPatchNoCache(self, img, src):
        #   data,invvar = img.data,img.invvar
        #   img.shape = data.shape
        #   del img.data
        #   del img.invvar
        #   R = super(Tractor2,self).getModelPatchNoCache(img, src)
        #   img.data, img.invvar = data,invvar
    
    

    #run,camcol,field = 7164,4,273
    #band='g'
    run,camcol,field = 2662, 4, 111
    band='i'
    roi=[0,300,0,300]
    im,info = st.get_tractor_image(run, camcol, field, band,
                                   useMags=True, roi=roi)
    sources = st.get_tractor_sources(run, camcol, field, band, roi=roi)
    tractor = Tractor2([im], sources)
    print tractor
    print tractor.getLogProb()
    tractor.freezeParam('images')

    p0 = tractor.getParams()
    tractor.setParams(p0)

    print
    print 'With Debug:'
    tractor.setParams(p0)
    tractor.mp = dmup
    t0 = Time()
    tractor.opt2()

sras, sdecs, smags = tychoMatch(ra,dec,(fieldradius*1.5)/60.)

    for sra,sdec,smag in zip(sras,sdecs,smags):
        print(sra,sdec,smag)

    imkw = dict(psf='dg')
    if dr9:
        getim = st.get_tractor_image_dr9
        getsrc = st.get_tractor_sources_dr9
        imkw.update(zrange=[-3,100])
    elif dr8:
        getim = st.get_tractor_image_dr8
        getsrc = st.get_tractor_sources_dr8
        imkw.update(zrange=[-3,100])
    else:
        getim = st.get_tractor_image
        getsrc = st.get_tractor_sources_dr8
        imkw.update(useMags=True)

    bands=['u','g','r','i','z']
    bandname = 'r'
    flipBands = ['r']
    print(rcfs)

    imsrcs = mp.map(get_ims_and_srcs, [(rcf + (bands, ra, dec, fieldradius*60./0.396, imkw, getim, getsrc))
                                       for rcf in rcfs])
    timgs = []
    sources = []
    allsources = []
    for ims,s in imsrcs:
        if ims is None:
            continue

def makeTractor(bands, ra, dec, S, RCFS):
	TI = []
	for i,(run,camcol,field) in enumerate(RCFS):

		for bandname in bands:
			im,inf = st.get_tractor_image(run, camcol, field, bandname,
										  useMags=True,
										  roiradecsize=(ra,dec,S))
			#im.dxdy = (fxc - xc, fyc - yc)
			TI.append((im,inf))
			if i == 0 and bandname == 'r':
				wcs = im.getWcs()
				# im,info = TI[bands.index('r')]
				#wcs = im.getWcs()
				# this is a shifted WCS; S,S is the center.
				# rd = wcs.pixelToPosition(None, (S,S))
				# ra,dec = rd.ra,rd.dec
				# print 'RA,Dec', ra,dec
				cd = wcs.cdAtPixel(xc,yc)
				pixscale = np.sqrt(np.abs(np.linalg.det(cd)))
				print('pixscale', pixscale * 3600.)
				extent = pixscale * S