If your image is single-channel (mode "L"), then you can use the eval
function:
img = Image.open("onechannel.png")
# at each pixel, if it isn't zero, make it 255..
better = Image.eval(img, lambda p: 255 * (int(p != 0)))
better.save("bilevel.png")
--Ned.
http://nedbatchelder.com
Karsten Hiddemann wrote:
Mike Meisner schrieb:
I'd like to use PIL to prep an image file to improve OCR quality.
Specifically, I need to filter out all but black pixels from the
image (i.e., convert all non-black pixels to white while retaining
the black pixels).
You could do something like the following:
from PIL import Image
img = Image.open("sample.png")
(xdim, ydim) = img.size
# this assumes that no alpha-channel is set
black = (0, 0, 0)
white = (255, 255, 255)
if Image.VERSION >= "1.1.6":
data = img.load()
for y in range(ydim-1, 0, -1):
for x in range(xdim):
if data[x,y] != black:
data[x,y] = white
else:
data = img.getdata()
for y in range(ydim-1, 0, -1):
for x in range(xdim):
if data[x+y*xdim] != black:
data[x+y*xdim] = white
img.save("sample-filtered.png")
_______________________________________________
Image-SIG maillist - Image-SIG@python.org
http://mail.python.org/mailman/listinfo/image-sig
--
Ned Batchelder, http://nedbatchelder.com
_______________________________________________
Image-SIG maillist - Image-SIG@python.org
http://mail.python.org/mailman/listinfo/image-sig
