On Thu, Feb 09, 2012 at 12:40:49PM -0500, Chris Mitchell wrote: > For a linear equation, you would want do use this: > > outJ = outI.point(lambda i:(i-y)*x)
I think this should be outJ = outI.point(lambda i:(i-lo)*x), but the point conversion method doesn't deal with these lambda definitions. My definition of y should have been "y = -lo*x" which brings my code to an algebraic equivalent to what I think Chris intends. This point conversion is only appropriate for use of the show method of the new image. Although outJ.show() creates a properly formed Netpbm PGM "rawbits" image, if outJ is saved, the resulting grayscale png file is black because it's a grayscale image which has been scaled down a lot. The single statement outI.point(lambda i:i*x+y).show() avoids the temptation to save the rescaled image. :-) ----------------------------------------------------- Although this design gives a non-white image, it is flawed in that the displayed image has greater contrast than the original. This is because the image under discussion doesn't use the full 16 bit "I" mode range of 0 to 65535. My code maps a lesser source range to 0 to 255 instead of 32 to 236 which would preserve the contrast. So I propose a revised solution scale = 256.0/2**16 outI.point(lambda i:i*scale+0).show() This relies on the "I" mode image having 16 bit pixels. I couldn't find a way to determine the source pixel size in PIL. The description of "I" mode in pil-handbook.pdf says it's 32 bit, which suggests other grayscale files may use other pixel sizes. -- Randolph Bentson bent...@holmsjoen.com _______________________________________________ Image-SIG maillist - Image-SIG@python.org http://mail.python.org/mailman/listinfo/image-sig
