# $Id: PowersOfTwo.py,v 1.3 2005/06/27 15:29:09 migurski Exp $ import math from PIL import Image chatty_default = False efficient_default = True def prepare(filename, chatty=chatty_default): """ Prepare a large image for tiling. Load an image from a file. Resize the image so that it is square, with dimensions that are an even power of two in length (e.g. 512, 1024, 2048, ...). Then, return it. """ src = Image.open(filename) if chatty: print "original size: %s" % str(src.size) full_size = (1, 1) while full_size[0] < src.size[0] or full_size[1] < src.size[1]: full_size = (full_size[0] * 2, full_size[1] * 2) img = Image.new('RGBA', full_size) src.thumbnail(full_size, Image.ANTIALIAS) img.paste(src, (int((full_size[0] - src.size[0]) / 2), int((full_size[1] - src.size[1]) / 2))) if chatty: print "full size: %s" % str(full_size) return img def tile(im, level, quadrant=(0, 0), size=(256, 256), efficient=efficient_default, chatty=chatty_default): """ Extract a single tile from a larger image. Given an image, a zoom level (int), a quadrant (column, row tuple; ints), and an output size, crop and size a portion of the larger image. If the given zoom level would result in scaling the image up, throw an error - no need to create information where none exists. """ scale = int(math.pow(2, level)) if efficient: # efficient: crop out the area of interest first, then scale and copy it inverse_size = (float(im.size[0]) / float(size[0] * scale), float(im.size[1]) / float(size[1] * scale)) top_left = (int(quadrant[0] * size[0] * inverse_size[0]), int(quadrant[1] * size[1] * inverse_size[1])) bottom_right = (int(top_left[0] + (size[0] * inverse_size[0])), int(top_left[1] + (size[1] * inverse_size[1]))) if inverse_size[0] < 1.0 or inverse_size[1] < 1.0: raise Exception('Requested zoom level (%d) is too high' % level) if chatty: print "crop(%s).resize(%s)" % (str(top_left + bottom_right), str(size)) zoomed = im.crop(top_left + bottom_right).resize(size, Image.ANTIALIAS).copy() return zoomed else: # inefficient: copy the whole image, scale it and then crop out the area of interest new_size = (size[0] * scale, size[1] * scale) top_left = (quadrant[0] * size[0], quadrant[1] * size[1]) bottom_right = (top_left[0] + size[0], top_left[1] + size[1]) if new_size[0] > im.size[0] or new_size[1] > im.size[1]: raise Exception('Requested zoom level (%d) is too high' % level) if chatty: print "resize(%s).crop(%s)" % (str(new_size), str(top_left + bottom_right)) zoomed = im.copy().resize(new_size, Image.ANTIALIAS).crop(top_left + bottom_right).copy() return zoomed def subdivide(img, level=0, quadrant=(0, 0), size=(256, 256), filename='tile-%d-%d-%d.jpg'): """ Recursively subdivide a large image into small tiles. Given an image, a zoom level (int), a quadrant (column, row tuple; ints), and an output size, cut the image into even quarters and recursively subdivide each, then generate a combined tile from the resulting subdivisions. If further subdivision would result in scaling the image up, use tile() to turn the image itself into a tile. """ if img.size[0] <= size[0] * math.pow(2, level): # looks like we've reached the bottom - the image can't be # subdivided further. # extract a tile from the passed image. out_img = tile(img, level, quadrant=quadrant, size=size) out_img.save(filename % (level, quadrant[0], quadrant[1])) print '.', ' ' * level, filename % (level, quadrant[0], quadrant[1]) return out_img # haven't reach the bottom. # subdivide deeper, construct the current image out of deeper images. out_img = Image.new('RGBA', (size[0] * 2, size[1] * 2)) out_img.paste(subdivide(img, level=(level + 1), quadrant=((quadrant[0] * 2) + 0, (quadrant[1] * 2) + 0), filename=filename), (0, 0 )) out_img.paste(subdivide(img, level=(level + 1), quadrant=((quadrant[0] * 2) + 0, (quadrant[1] * 2) + 1), filename=filename), (0, size[1])) out_img.paste(subdivide(img, level=(level + 1), quadrant=((quadrant[0] * 2) + 1, (quadrant[1] * 2) + 0), filename=filename), (size[0], 0 )) out_img.paste(subdivide(img, level=(level + 1), quadrant=((quadrant[0] * 2) + 1, (quadrant[1] * 2) + 1), filename=filename), (size[0], size[1])) out_img = out_img.resize(size, Image.ANTIALIAS) out_img.save(filename % (level, quadrant[0], quadrant[1])) print '-', ' ' * level, filename % (level, quadrant[0], quadrant[1]) return out_img if __name__ == '__main__': import sys img = prepare(sys.argv[-1], chatty=True) tile(img, 0, chatty=True).show() #tile(img, 1, quadrant=(0, 0), chatty=True).show() #tile(img, 1, quadrant=(1, 0), chatty=True).show() #tile(img, 1, quadrant=(0, 1), chatty=True).show() tile(img, 1, quadrant=(1, 1), chatty=True).show() #tile(img, 2, quadrant=(1, 1), chatty=True).show() #tile(img, 2, quadrant=(2, 1), chatty=True).show() #tile(img, 2, quadrant=(1, 2), chatty=True).show() tile(img, 2, quadrant=(2, 2), chatty=True).show() #tile(img, 3, quadrant=(3, 3), chatty=True).show() #tile(img, 3, quadrant=(4, 3), chatty=True).show() #tile(img, 3, quadrant=(3, 4), chatty=True).show() tile(img, 3, quadrant=(4, 4), chatty=True).show() #tile(img, 4, quadrant=(7, 7), chatty=True).show() #tile(img, 4, quadrant=(8, 7), chatty=True).show() #tile(img, 4, quadrant=(7, 8), chatty=True).show() tile(img, 4, quadrant=(8, 8), chatty=True).show() #tile(img, 4, quadrant=(15, 15), chatty=True).show() #tile(img, 4, quadrant=(16, 15), chatty=True).show() #tile(img, 4, quadrant=(15, 16), chatty=True).show() tile(img, 5, quadrant=(16, 16), chatty=True).show()