Python Pil Change GreyScale Tif To RGB

Question

I have a greyscale TIF File. I need to convert it to RGB/ read from it in a way I can work with it.

img = Image.open(GIF_FILENAME)
rgbimg = img.convert('RGB')
for i in range(5):
    print rgbimg.getpixel((i, 0))

The convert.("RGB") will automatically make everything (255,255,255) even though the picture is a really dark mostly black picture.

If I just read the greyscale numbers I get numbers from around 1400 to 1900.

I need to also save a copy of the picture as a RGB Jpeg. Picture in question: [Here]: https://i.stack.imgur.com/AuNJh.jpg

How would I go along doing this?

Answer 1

what about:

img = Image.open(GIF_FILENAME)
rgbimg = Image.new("RGBA", img.size)
rgbimg.paste(img)
rgbimg.save('foo.jpg')

[EDIT]

created a test:

from PIL import Image
from collections import defaultdict
import pprint

img = Image.open("kEwfFs3.png")
rgbimg = Image.new("RGBA", img.size)
rgbimg.paste(img)

found_colors = defaultdict(int)
for x in range(0, rgbimg.size[0]):
    for y in range(0, rgbimg.size[1]):
        pix_val = rgbimg.getpixel((x, y))
        found_colors[pix_val] += 1 
pprint.pprint(dict(found_colors))

rgbimg.save('kEwfFs3.jpg')

And that outputs:

{(0, 0, 0, 255): 747802,
 (1, 1, 1, 255): 397,
 (2, 2, 2, 255): 299,
 (3, 3, 3, 255): 255,
 (4, 4, 4, 255): 221,
 (5, 5, 5, 255): 200,
 (6, 6, 6, 255): 187,
 (7, 7, 7, 255): 138,
 (8, 8, 8, 255): 160,
 (9, 9, 9, 255): 152,
 (10, 10, 10, 255): 122,
 (11, 11, 11, 255): 116,
 (12, 12, 12, 255): 144,
 (13, 13, 13, 255): 117,
 (14, 14, 14, 255): 117,
 (15, 15, 15, 255): 102,
 (16, 16, 16, 255): 119,
 (17, 17, 17, 255): 299641,
 (18, 18, 18, 255): 273,
 (19, 19, 19, 255): 233,
.................... etc .......
.................... etc .......
 (249, 249, 249, 255): 616,
 (250, 250, 250, 255): 656,
 (251, 251, 251, 255): 862,
 (252, 252, 252, 255): 1109,
 (253, 253, 253, 255): 1648,
 (254, 254, 254, 255): 2964175}

Which is what you would expect. Is your output different?

Answer 2

I ran into the same problem with an I;16 (16-bit grayscale) tiff, converted to RGB. Some digging into the manual reveals the problem has to do with the lut PIL is using to convert grayscale images to RGB. It is working in an 8-bit color space; that is it clips all values above 255. So a quick and simple solution is to manually convert to RGB using your own lut which scales the values within range using the point method like so:

path = 'path\to\image'
img = Image.open(path)
img.point(lambda p: p*0.0039063096, mode='RGB')
img = img.convert('RGB')
img.show() # check it out!

I determined the "lut" formula by just dividing 256 by the 16-bit equivalent, 65535.