Hi Will, Will Henney wrote: > How about this for a numpy implementation? Runs nearly as fast as the C > version > on my mac (1.58 vs 1.16 secs). This is great! I get about 0.34 vs 0.55. The numpy implementation is darn good for a python only implementation. There is a subtle difference in the output though, this version seems to create a what appears as a slightly 'noisier' result, the python and C versions I did were identical to the eye at least at 1:1. Not sure exactly why this would be perhaps a value is clipping somewhere? Could be also there is a consistent error in my two implementations.
I upgraded my numpy to the latest version and now it works with the latest PIL, so I will have to revisit the other simple pixel setting test that didn't work at all for me before. I have also looked at the performance python article (http://www.scipy.org/PerformancePython) that was forwarded through to me (thanks Sebastian!) which looks like it opens up yet more convenient performance options with the weave modules, particularly now that I have numpy working with PIL. Lots to explore still it seems! Thanks for the example, Cheers, JB. > def hillShadeNumPy(filenameIn, filenameOut, scale=1.0, azdeg=315.0, > altdeg=45.0): > ''' Create a hill shade version of the given image using numpy ''' > from numpy import sin, cos, hypot, arctan, arctan2, pi > > dScale = (1.0 * scale) > # convert alt, az to radians > az = azdeg*pi/180.0 > alt = altdeg*pi/180.0 > (img, data, imgS, dataS) = initialiseImages(filenameIn) > > # get the image data as a numpy array of floats > adata = N.asarray(img).astype('float') > # gradient in x and y directions > dx, dy = N.gradient(adata/dScale) > slope = 0.5*pi - arctan(hypot(dx, dy)) > aspect = arctan2(dx, dy) > c = sin(alt)*sin(slope) + cos(alt)*cos(slope)*cos(-az - aspect - 0.5*pi) > c = N.where(c > 0.0, c*255.0, 0.0) > imgS = Image.fromarray(c.astype('uint8')) > imgS.save(filenameOut,'PNG') -- John Barratt - www.langarson.com.au Python, Zope, GIS, Weather _______________________________________________ Image-SIG maillist - Image-SIG@python.org http://mail.python.org/mailman/listinfo/image-sig
