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copied!<p>I blindly implemented the formulas from <a href="http://wiki.panotools.org/Fisheye_Projection" rel="nofollow noreferrer">here</a>, so I cannot guarantee it would do what you need.</p> <p>Use <code>auto_zoom</code> to get the value for the <code>zoom</code> parameter.</p> <pre><code> def dist(x,y): return sqrt(x*x+y*y) def fisheye_to_rectilinear(src_size,dest_size,sx,sy,crop_factor,zoom): """ returns a tuple of dest coordinates (dx,dy) (note: values can be out of range) crop_factor is ratio of sphere diameter to diagonal of the source image""" # convert sx,sy to relative coordinates rx, ry = sx-(src_size[0]/2), sy-(src_size[1]/2) r = dist(rx,ry) # focal distance = radius of the sphere pi = 3.1415926535 f = dist(src_size[0],src_size[1])*factor/pi # calc theta 1) linear mapping (older Nikon) theta = r / f # calc theta 2) nonlinear mapping # theta = asin ( r / ( 2 * f ) ) * 2 # calc new radius nr = tan(theta) * zoom # back to absolute coordinates dx, dy = (dest_size[0]/2)+rx/r*nr, (dest_size[1]/2)+ry/r*nr # done return (int(round(dx)),int(round(dy))) def fisheye_auto_zoom(src_size,dest_size,crop_factor): """ calculate zoom such that left edge of source image matches left edge of dest image """ # Try to see what happens with zoom=1 dx, dy = fisheye_to_rectilinear(src_size, dest_size, 0, src_size[1]/2, crop_factor, 1) # Calculate zoom so the result is what we wanted obtained_r = dest_size[0]/2 - dx required_r = dest_size[0]/2 zoom = required_r / obtained_r return zoom </code></pre>

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