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@muminoff
Created June 17, 2017 16:28
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Equirectangular panorama to cube map (Python 3)
import sys
from PIL import Image
from math import pi,sin,cos,tan,atan2,hypot,floor
from numpy import clip
# get x,y,z coords from out image pixels coords
# i,j are pixel coords
# face is face number
# edge is edge length
def outImgToXYZ(i,j,face,edge):
a = 2.0*float(i)/edge
b = 2.0*float(j)/edge
if face==0: # back
(x,y,z) = (-1.0, 1.0-a, 3.0 - b)
elif face==1: # left
(x,y,z) = (a-3.0, -1.0, 3.0 - b)
elif face==2: # front
(x,y,z) = (1.0, a - 5.0, 3.0 - b)
elif face==3: # right
(x,y,z) = (7.0-a, 1.0, 3.0 - b)
elif face==4: # top
(x,y,z) = (b-1.0, a -5.0, 1.0)
elif face==5: # bottom
(x,y,z) = (5.0-b, a-5.0, -1.0)
return (x,y,z)
# convert using an inverse transformation
def convertBack(imgIn,imgOut):
inSize = imgIn.size
outSize = imgOut.size
inPix = imgIn.load()
outPix = imgOut.load()
edge = inSize[0]/4 # the length of each edge in pixels
for i in range(outSize[0]):
face = int(i/edge) # 0 - back, 1 - left 2 - front, 3 - right
if face==2:
rng = range(0,int(edge*3))
else:
rng = range(int(edge), int(edge) * 2)
for j in rng:
if j<edge:
face2 = 4 # top
elif j>=2*edge:
face2 = 5 # bottom
else:
face2 = face
(x,y,z) = outImgToXYZ(i,j,face2,edge)
theta = atan2(y,x) # range -pi to pi
r = hypot(x,y)
phi = atan2(z,r) # range -pi/2 to pi/2
# source img coords
uf = ( 2.0*edge*(theta + pi)/pi )
vf = ( 2.0*edge * (pi/2 - phi)/pi)
# Use bilinear interpolation between the four surrounding pixels
ui = floor(uf) # coord of pixel to bottom left
vi = floor(vf)
u2 = ui+1 # coords of pixel to top right
v2 = vi+1
mu = uf-ui # fraction of way across pixel
nu = vf-vi
# Pixel values of four corners
# import sys
# print('inPix ->', inPix)
# print('ui ->', ui)
# print('inSize[0]', inSize[0])
# bar = clip(vi,0,inSize[1]-1)
# print('bar ->', bar, type(bar), int(bar))
# baz = ui % inSize[0]
# print('baz ->', baz, type(baz))
# foo = inPix[ui % inSize[0], bar]
# sys.exit(-1)
A = inPix[ui % inSize[0],int(clip(vi,0,inSize[1]-1))]
B = inPix[u2 % inSize[0],int(clip(vi,0,inSize[1]-1))]
C = inPix[ui % inSize[0],int(clip(v2,0,inSize[1]-1))]
D = inPix[u2 % inSize[0],int(clip(v2,0,inSize[1]-1))]
# interpolate
(r,g,b) = (
A[0]*(1-mu)*(1-nu) + B[0]*(mu)*(1-nu) + C[0]*(1-mu)*nu+D[0]*mu*nu,
A[1]*(1-mu)*(1-nu) + B[1]*(mu)*(1-nu) + C[1]*(1-mu)*nu+D[1]*mu*nu,
A[2]*(1-mu)*(1-nu) + B[2]*(mu)*(1-nu) + C[2]*(1-mu)*nu+D[2]*mu*nu )
outPix[i,j] = (int(round(r)),int(round(g)),int(round(b)))
imgIn = Image.open(sys.argv[1])
inSize = imgIn.size
i1 = inSize[0]
imgOut = Image.new("RGB",(inSize[0],int(inSize[0]*3/4)),"black")
convertBack(imgIn,imgOut)
imgOut.save(sys.argv[1].split('.')[0]+"Out2.png")
imgOut.show()
@humoyun
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humoyun commented Apr 23, 2019

Oo thanks, exactly what I was looking for. (much easier than dealing with Hugin for conversion)

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