python - not creating image

Question

I am trying to import an image, then manipulate its rgb colors. This is what i've got:

from PIL import Image
image = Image.open('grapes.jpg')
pixels = list(image.getdata())

for pixel in pixels:
    pixel = (pixel[0] - 50, pixel[1] , pixel[2])

image.putdata(pixel)
image.save('grapes_modified.jpg')

as you can see, i am trying to reduce the red channel. This doesn't work. It produces the exact duplicate of the imported image. even if i where to do something like this: pixel = (0,0,0). It would produce a duplicate image.

so how do i modify the image?

thanks,

Joril · Accepted Answer · 2011-10-07 13:52:11Z

3

The for cycle doesn't replace the content of each pixel, it just creates a new instance and then tosses it away. You should create a new array, for example:

newdata = [ (pixel[0] - 50, pixel[1] , pixel[2]) for pixel in pixels ]

answered Oct 7, 2011 at 13:52

Joril

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