Displaying Images#
Since Firefly was originally developed to visualize data products from astronomical archives, displaying an image is a two-step process of uploading a file and then showing it. The examples here use the data products downloaded in Getting Started.
The FireflyClient.upload_file() method uploads the file and
returns a location understood by the Firefly server. The location
string is passed to FireflyClient.show_fits() to display
the image. In the display step,
it is recommended to explicitly specify the plot_id parameter
for later use in modifying the image display.
fval = fc.upload_file('2mass-m31-green.fits')
fc.show_fits(fval, plot_id='m31-green', title='2MASS H, M31')
Modifying an Image Display#
Zooming, panning, and changing the stretch (mapping of pixels to display values) is accomplished by corresponding methods, passing in the plot_id as the first argument.
fc.set_zoom('m31-green', 4)
fc.set_pan('m31-green', 200, 195)
fc.set_stretch('m31-green', 'sigma', 'log', lower_value=-2, upper_value=30)
A “zscale” stretch may be commanded with alternate parameters:
fc.set_stretch('m31-green', 'zscale', 'linear')
At present the API does not include a function for changing the color map
for the image. The relevant Javascript action may be invoked using
FireflyClient.dispatch():
fc.dispatch(action_type='ImagePlotCntlr.ColorChange',
payload={'plotId': 'm31-green',
'cbarId': 16})
The colormap can be reverted to the original grayscale by using the command above together with ‘cbarId’ : 0.
Specifying Zoom and Stretch Values When First Displaying an Image#
It is often advantageous to specify the zoom, stretch, and color table parameters in the same command that displays the image, to avoid problems with the later commands being ignored when the image display has not completed.
To specify the stretch as part of the image display, you can generate a range values string. This example is for an asinh stretch with a Q value of 6 and an upper level of 98 percent:
rvstring = fc._create_rangevalues_standard(algorithm='asinh',
asinh_q_value=6,
upper_value=98.0)
The zoom value can be specified in several different ways. When displaying images with different pixel scales, the best practice is to specify ZoomType=’ARCSEC_PER_SCREEN_PIX’ and then the numerical value, e.g. ZoomArcsecPerScreenPix=0.3.
The color table is specified with an integer. The pan point can be specified with parameter WorldPt. For example:
size_in_arcsec = 400
ra = 150.00983
dec = 2.59783
target = '{};{};EQ_J2000'.format(ra, dec)
fc.show_fits(plot_id='IRAC1',
Title='COSMOS 3.6um',
Type='SERVICE',
Service='ATLAS',
SurveyKey='cosmos.cosmos_irac',
SurveyKeyBand='IRAC1',
WorldPt=target,
SizeInDeg=size_in_arcsec/3600,
ColorTable=1,
ZoomType='ARCSEC_PER_SCREEN_PIX',
ZoomArcsecPerScreenPix=0.3,
RangeValues=rvstring)
Turning On WCS Locking#
When multiple images covering the same sky location are displayed, you can align and lock by sky coordinates. To lock and align by world coordinates:
fc.align_images(lock_match=True)
Retrieving Images Using IRSA-Specific Searches#
Firefly includes image search processors for Infrared Science Archive (IRSA) image holdings. A table of available projects for image searches is maintained in the Firefly code base. The information can be retrieved into an Astropy table:
from astropy.table import Table
surveys = Table.read('https://raw.githubusercontent.com/Caltech-IPAC/firefly/dev/src/firefly/' +
'java/edu/caltech/ipac/firefly/resources/irsa-image-master-table.csv',
format='csv')
To select images available for the COSMOS project:
cosmos_surveys = surveys[surveys['missionId'] == 'COSMOS']
To search the survey:
size_in_arcsec = 200
ra = 150.00983
dec = 2.59783
target = '{};{};EQ_J2000'.format(ra, dec)
fc.show_fits(plot_id='IRAC1',
Title='COSMOS 3.6um',
Type='SERVICE',
Service='ATLAS',
SurveyKey='cosmos.cosmos_irac',
SurveyKeyBand='IRAC1',
WorldPt=target,
SizeInDeg=size_in_arcsec/3600,
ColorTable=1,
ZoomType='ARCSEC_PER_SCREEN_PIX',
ZoomArcsecPerScreenPix=0.3,
RangeValues=rvstring)
Displaying HiPS Images#
While the above examples involve displaying FITS images, it’s also possible to view a HiPS image using a different method that involves specifying the base URL where the target search is performed. To search the survey:
hips_url = 'https://irsa.ipac.caltech.edu/data/hips/CDS/2MASS/Color/'
size_in_deg = 0.2
ra = 274.700727
dec = -13.807228
target = '{};{};EQ_J2000'.format(ra, dec)
fc.show_hips(viewer_id='hipspc1',
plot_id='HipsID1-1',
hips_root_url = hips_url,
Title='HiPS-2m',
WorldPt=target,
SizeInDeg=size_in_deg)
Displaying 3-Color Images#
It is possible to create a 3-color composite image using a list of dictionaries containing included parameters on all given bands (or simply one dictionary for that band). For example:
rv = '92,-2,92,8,NaN,2,44,25,600,120'
ra = 210.80227
dec = 54.34895
target = '{};{};EQ_J2000'.format(ra, dec)
threeC= [
{
'Type' : 'SERVICE',
'Service' : 'WISE',
'Title' : '3 color',
'SurveyKey' : '3a',
'SurveyKeyBand': '3',
'WorldPt' : target,
'RangeValues': rv,
'SizeInDeg' : '.14'
},
{
'Type' : 'SERVICE',
'Service' : 'WISE',
'Title' : '3 color',
'SurveyKey' : '3a',
'SurveyKeyBand': '2',
'WorldPt' : target,
'RangeValues': rv,
'SizeInDeg' : '.14'
},
{
'Type' : 'SERVICE',
'Service' : 'WISE',
'Title' : '3 color',
'SurveyKey' : '3a',
'SurveyKeyBand': '1',
'WorldPt' : target,
'RangeValues': rv,
'SizeInDeg' : '.14'
}]
fc.show_fits_3color(threeC,
plot_id='wise_m101',
viewer_id='3C')
Displaying Image from a URL#
If you have the URL of an image, you can pass it directly instead of downloading it and then uploading it to firefly:
image_url = 'http://irsa.ipac.caltech.edu/ibe/data/wise/allsky/4band_p1bm_frm/6a/02206a/149/02206a149-w1-int-1b.fits?center=70,20&size=200pix'
fc.show_fits(url=image_url, plot_id='wise-allsky', title='WISE all-sky')