# Read SRTM3 file and create shaded relief# 2010-04-05from struct import unpack,calcsizefrom numpy import *import numpy as npfrom PIL import Imagerow_length = 1201# row_length is 1201 for SRTM3 or 3601 for SRTM1file_name  = "N40E014.hgt"# from http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/Eurasia/hlim       = 800# height limit for map [m]ref_lat    = 40.55# reference latitudeearth_eq   = 6371. * 1000. * 2. * pix_scale    = 1./360.*earth_eq*cos(ref_lat/180.*pi)/row_lengthy_scale    = 1./360.*earth_eq/row_lengthprint "1 pixel = %u * %u m" % (x_scale, y_scale)print "factor", y_scale/x_scaleh = zeros((row_length, row_length))f = open(file_name, 'r')li = []for j in range(row_length):for i in range(row_length):d = f.read(2)(height,) = unpack('>h', d)h[i,j] = heightif height < -1000:li.append((i,j))hmax = h.max()h3 = zeros_like(h)h3[:,:] = h[:,:]print len(li), "missing data points"def get_nei(z):h2 = h[z[0]-1:z[0]+2,z[1]-1:z[1]+2]nn = sum(where(h2 < -1000, 0, 1))av = sum(where(h2 > -1000, h2, 0)) / float(nn)return nn, av# fill missing points with a nearest-neighbor averaging method:loop = len(li)lim = 7while loop > 0:sd = Falsefor q in range(len(li)):if h[li[q]] > -1000.: continuen, a = get_nei(li[q])if n >= lim:print li[q],loop, n, a, limh3[li[q]] = aloop -= 1sd = Trueif not sd: lim -= 1h[:,:] = h3[:,:]print "missing points done"def hext(a):"Hex color to triplet."r,g,b = a[0:2], a[2:4], a[4:6]return int(r, 16), int(g, 16), int(b, 16)# from http://en.wikipedia.org/wiki/Wikipedia:WikiProject_Maps/Conventions/Topographic_maps:col_sea = hext("0978ab")cols = """{{Mapcolor|r=245|v=244|b=242|hex=#F5F4F2|col=black}}{{Mapcolor|r=224|v=222|b=216|hex=#E0DED8|col=black}}{{Mapcolor|r=202|v=195|b=184|hex=#CAC3B8|col=black}}{{Mapcolor|r=186|v=174|b=154|hex=#BAAE9A|col=black}}{{Mapcolor|r=172|v=154|b=124|hex=#AC9A7C|col=black}}{{Mapcolor|r=170|v=135|b=83|hex=#AA8753|col=black}}{{Mapcolor|r=185|v=152|b=90|hex=#B9985A|col=black}}{{Mapcolor|r=195|v=167|b=107|hex=#C3A76B|col=black}}{{Mapcolor|r=202|v=185|b=130|hex=#CAB982|col=black}}{{Mapcolor|r=211|v=202|b=157|hex=#D3CA9D|col=black}}{{Mapcolor|r=222|v=214|b=163|hex=#DED6A3|col=black}}{{Mapcolor|r=232|v=225|b=182|hex=#E8E1B6|col=black}}{{Mapcolor|r=239|v=235|b=192|hex=#EFEBC0|col=black}}{{Mapcolor|r=225|v=228|b=181|hex=#E1E4B5|col=black}}{{Mapcolor|r=209|v=215|b=171|hex=#D1D7AB|col=black}}{{Mapcolor|r=189|v=204|b=150|hex=#BDCC96|col=black}}{{Mapcolor|r=168|v=198|b=143|hex=#A8C68F|col=black}}{{Mapcolor|r=148|v=191|b=139|hex=#94BF8B|col=black}}{{Mapcolor|r=172|v=208|b=165|hex=#ACD0A5|col=black}}"""col = []for l in cols.splitlines():if len(l) < 10: continuei = l.find('#')if i > -1:col.append(hext(l[i+1:i+7]))col.reverse()# -> bottom to topo = Image.new('RGB', h.shape)def interp(c, f):"Interpolate into color table."r = int((1.-f) * col[c][0] + f * col[c+1][0])g = int((1.-f) * col[c][1] + f * col[c+1][1])b = int((1.-f) * col[c][2] + f * col[c+1][2])return r,g,bfor j in range(row_length):for i in range(row_length):c, f = divmod(h[j,i] / hmax * (len(col)-1), 1)if 0 < h[j,i] < hmax:o.putpixel((j,i), interp(int(c), f))elif h[i,j] == hmax:o.putpixel((j,i), col[-1])else: o.putpixel((j,i), col_sea)o.save("map_height.png")# save height mapo2 = o.crop((0,0,942,603))o2.save("map_height_cropped.png")# taken from hillshade.py:#def illumination(idata,azdeg=315.0,altdeg=45.):def illumination(idata,azdeg=225.0,altdeg=45.):    # convert alt, az to radians    az = azdeg*np.pi/180.0    alt = altdeg*np.pi/180.0    # gradient in x and y directions    dx, dy = np.gradient(idata)    slope = 0.5*np.pi - np.arctan(np.hypot(dx, dy))    aspect = np.arctan2(dx, dy)    odata = np.sin(alt)*np.sin(slope) + np.cos(alt)*np.cos(slope)*np.cos(-az -\             aspect - 0.5*np.pi)    # rescale to interval -1,1    # 1 means maximum sun exposure and 0 means complete shade.    odata = (odata - odata.min())/(odata.max() - odata.min())    return odatail = 255 * illumination(h)o4 = Image.new('RGBA', il.shape)for j in range(row_length-1):for i in range(row_length-1):v = int(il[j,i])if 0 <= v < 128:alpha = (255 - 2*v)o4.putpixel((j,i), (0,0,0,alpha))elif v == 128:o4.putpixel((j,i), (0,0,0,0))elif 128 < v < 256:alpha = 2*(v-128)o4.putpixel((j,i), (255,255,255,alpha))else:o4.putpixel((j,i), (255,255,255,0))o4.save("il_NW_alpha.png")# NW-illuminated (alpha transparency for use with Inkscape)