def sky2pix(self, coordinate, origin=0):
r"""
Calculates the Pixel corresponding to a given coordinate.
Parameters
----------
coordinate : list
Either ['RA','DEC'], e.g. ['1:34:7.00', '+30:47:52.00'] in
equatorial coordinates or [RA, DEC] in GRAD.
origin : int
``0`` or ``1``; this steers how the first pixel is counted
``0`` is for usage with python as it starts to count from zero.
``1`` is the fits standart.
Returns
-------
pixel : List
[x, y]; the pixel coordinates of the map.
"""
# Equatorial_to_degrees is only possible to execute if coordinate is in
# the correct form for RA DEC.
self.log.debug("Calculate map pixel for coord. {}".format(coordinate))
try:
self.log.debug("Test trying to convert coord. to degrees")
coordinate = astFunc.equatorial_to_degrees(coordinate)
self.log.debug("Calculated coordinate in "\
"Degrees: {}".format(coordinate))
except AttributeError:
self.log.debug("Conversion to degrees failed. "\
"This does not have to be a problem.")
coordinate = np.array([[coordinate[0], coordinate[1]]], np.float_)
self.log.debug("Retrieving the pixels of the map at given coordinate")
sky2pix_result = self.wcs.wcs_world2pix(coordinate, origin)
pixel = sky2pix_result[0]
# The pixels are floats. To get integers we get the floor value
# of the floats
pixel = [int(math.floor(float(pixel[0]))),
int(math.floor(float(pixel[1])))]
self.log.debug("Output pixel {}".format(pixel))
return pixel
def read_aperture(self, position, apertureSize=0, backgroundSize=0,
output=False, annotation=False, newAnnotation=False):
# TODO: needs better scheme for the header keywords. Migth not work
# with all maps.
r"""
Extract the sum and mean flux inside an aperture of a given size
and at a given position..
This function can be used to read the flux in the area of a circular
aperture, as well as to correct for the background flux.
Parameters
----------
position : list
The position in RA,DEC where the aperture is to be applied.
The Format has to be either:
* ['RA','DEC'] with strings representing equatorial
coordinates, e.g. ['01:34:32.8', '+30:47:00.6'].
or:
* [RA, DEC] where RA and DEC being the coordinates in Grad.
apertureSize : float [arcsec]
The diameter of the aperture to be applied.
backgroundSize : float [arcsec]
The Size of the Anulli in which the background is to be
estimated. The number to be given here correspond to the diameter
of the circle in [arcsec ] descibing the outer border of the
annuli, measured from the position given in position. Thus, the
background is measurd in the ring described by apertureSize and
backgroundSize. Default is 0 and thus **no background substaction**
is applied.
output : True or False
If True the function reports the calculated values during
execution.
annotion : logical
If True a kvis annotation file ``"apertures.ann"`` containing the
aperture used to integrate the flux is created. Default is False,
i.e. not to create the aperture.
newAnnotation : logical
If True ``"apertures.ann"`` is overwritten. If False an old
``"apertures.ann"`` is used to append the new apertures. If it not
exists a new one is created. The latter is the default.
Returns
-------
List : [Sum, Mean, Number of pixels]
Notes
-----
The pixel sizes have to be quadratic for the algorithm to work. It
measures a circle by counting the pixels from the central pixel
corresponding to the given coordinate.
"""
self.log.debug(
"Determining the Flux at position: {}; "\
"in aperture of size {} and background of {}".format(
position, apertureSize, backgroundSize)
)
# Calculate the x,y Pixel coordinate of the position.
xCenter, yCenter = self.sky2pix(position)
# Read the pixel Size (normaly in Grad FITS-Standard)
try:
self.pixSize1 = float(self.header['CDELT1'])
self.pixSize2 = float(self.header['CDELT2'])
except:
# sometimes the header keywords are different.
try:
self.pixSize1 = float(self.header['XPIXSIZE'])
self.pixSize2 = float(self.header['YPIXSIZE'])
self.pixSize1 = self.pixSize1 / 60 / 60
self.pixSize2 = self.pixSize2 / 60 / 60
except:
print 'No Header keyword for the pixsize found'
sys.exit()
# Check if the pixel size is quadratic, if not the function does not
# work correctly (yet)
if ((((self.pixSize1) ** 2 - (self.pixSize2) ** 2) ** 2 <
((self.pixSize1) ** 2) * 0.01)):
if output is True:
print ('Pixel Size X: ' + str(self.pixSize1 / (1. / 60 / 60))
+ ' arcsec')
print ('Pixel Size Y: ' + str(self.pixSize2 / (1. / 60 / 60))
+ ' arcsec')
print ('Pixel Size quadratic to 1%, Go on with '
'calculation of Apertures')
else:
if output is True:
print self.pixSize1, self.pixSize2
print ('Pixel Size *NOT* quadratic: Exit the program, '
'please regrid!')
sys.exit()
# Convert the apertureSizes to Grad f
apertureSizeInGrad = (1. / 60 / 60) * (apertureSize) / 2
# Calculate how many pixels are needed to cover the radius of the
# aperture
apertureSteps = math.sqrt(math.floor(apertureSizeInGrad /
self.pixSize1) ** 2)
# same for the backround annuli
if backgroundSize != 0:
backgroundSizeInGrad = (1. / 60 / 60) * (backgroundSize) / 2
backgroundSteps = math.sqrt(math.floor(backgroundSizeInGrad /
self.pixSize1) ** 2)
x_max, x_min = xCenter + backgroundSteps, xCenter - backgroundSteps
y_max, y_min = yCenter + backgroundSteps, yCenter - backgroundSteps
else:
x_max, x_min = xCenter + apertureSteps, xCenter - apertureSteps
y_max, y_min = yCenter + apertureSteps, yCenter - apertureSteps
# calculate the x and y range in Pixel coordinates that are needed at
# most for the calculation of the aperture and background
# Now: Initialize variables
sum = 0 # will store the sum of all Pixels in the aperture
N = 0 # counts the number of pixels in the aperture to be able to
# calculate the mean
sumBackgnd = 0 # the sum of all pixels in the background
NBackgnd = 0 # number of pixels in the background
# calculate the background
if backgroundSize != 0:
for x in range(int(x_min), int(x_max)):
for y in range(int(y_min), int(y_max)):
if ((math.floor(math.sqrt((xCenter - x) ** 2 +
(yCenter - y) ** 2)) <
backgroundSteps and math.floor(math.sqrt((xCenter - x)
** 2 +
(yCenter - y)
** 2))
> apertureSteps)):
sumBackgnd += self.data[y][x]
NBackgnd += 1
backgndMean = sumBackgnd / NBackgnd
print backgndMean
# caclulate the sum in the aperture
for x in range(int(x_min), int(x_max)):
for y in range(int(y_min), int(y_max)):
if (math.floor(math.sqrt((xCenter - x) ** 2 + (yCenter - y) **
2)) < apertureSteps):
if backgroundSize != 0:
sum += self.data[y][x] - backgndMean
else:
sum += self.data[y][x]
N += 1
if backgroundSize != 0:
mean = (sum / N) - backgndMean
sumcorrected = sum - (N * backgndMean)
result = [sum, mean, N]
if backgroundSize == 0:
mean = (sum / N)
result = [sum, mean, N]
if output is True:
print ('Sum:', result[0], 'Mean:', result[1],
'Number of Pixel:', result[2])
if newAnnotation is False:
fileout = open('apertures.ann', 'a')
if newAnnotation is True:
fileout = open('apertures.ann', 'w')
if annotation is True:
position = astFunc.equatorial_to_degrees(position)
apertureString = ('CROSS ' +
str(position[0]) + ' ' +
str(position[1]) + ' 0.0008 0.001 \n'
'circle ' +
str(position[0]) + ' ' +
str(position[1]) + ' ' +
str(apertureSize * (1. / 60 / 60) / 2) + ' \n'
'text ' +
str(position[0] + (1. / 60 / 60)) + ' ' +
str(position[1] + (1. / 60 / 60)) + '\n')
fileout.write(apertureString)
fileout.close()
return result
