將泊松噪聲添加到擬合文件

Question

我試圖將增量的泊松噪聲添加到.fits文件。我知道如何做一個普通的文件類型，但我似乎無法讀取適合，然後添加泊松噪聲。有人知道如何去做這件事嗎？

這是代碼。其中大部分並不特別相關。

s=str(raw_input("filter name: ")) 
t=str(raw_input("sci or wht: ")) 
poisson = str(raw_input("Poisson noise amount: ")) 
for i in range(0,len(ra_new)): 
    ra_new2=cat['ra'][z2&lmass2&ra2&dec2][i] 
    dec_new2=cat['dec'][z2&lmass2&ra2&dec2][i] 
    id_new=cat['id'][z2&lmass2&ra2&dec2][i] 
    target_pixel_x = ((ra_new2-ra_ref)/(pixel_size_x))+reference_pixel_x  
    target_pixel_y = ((dec_new2-dec_ref)/(pixel_size_y))+reference_pixel_y 
    fig = plt.figure(figsize=(5.,5.)) 
    timage=img[target_pixel_y-65:target_pixel_y+65,target_pixel_x-65:target_pixel_x+65] 
    plt.imshow(img[target_pixel_y-65:target_pixel_y+65,target_pixel_x-65:target_pixel_x+65], vmin=-0.01, vmax=0.1, cmap='Greys') 

galimage = pf.writeto(t+'PHOTO'+s+str(i)+'.fits',timage,clobber=True,header=hdr) 
     imagea = (scipy.misc.imread(galimage)).astype(float) 
     poissonNoise = numpy.random.poisson(poisson,imagea.shape).astype(float) 
     noisyImage = imagea + poissonNoise 
     pf.writeto(t+'POISSONPHOTO'+s+str(i)+poisson+'.fits',timage,clobber=True,header=hdr) 
     lmass3=cat['lmass'][z2&lmass2&ra2&dec2][i] 
     print id_new, ra_new2,dec_new2 

Answer 1

我能正確解釋你的問題嗎？使用pyfits。

import numpy 
import scipy 
import pyfits 

# Use Pyfits to read in a file. 
im = pyfits.open("example.fits") 

# pyfits opens a "list" of all header extensions in the file. 
isinstance(im,list) 

# my example is a simple 2d image. so I want the first header unit 
im0 = im[0] 

# you access the data shape this way 
print im0.data.shape 

# simple check of the image variance 
print numpy.var(im0.data) 

# now I'm just repeating the same as your example 
poisson = str(raw_input("Poisson noise amount: ")) 
poissonNoise = numpy.random.poisson(poisson, im0.data.shape).astype(float) 
test = im0.data + poissonNoise 

# check things out and write to new file 
print numpy.var(test) 

# you could do this. 
im0.data = test 

# write that new image back out with the old header. 
pyfits.writeto("/tmp/test.fits", data=test, header=im0.header) 

# prove it worked. 
check = pyfits.open("/tmp/test.fits") 

numpy.var(check[0].data)