Making an image from the list

Question

I'm trying to create an image from list of 1s and 0s in Python.

from PIL import Image

img1 = Image.open('Image1.gif') #the image is strictly black and white
img1_size = img1.size 
img1_k = []
for i in range(img1_size[0]): 
    for j in range(img1_size[1]): 
        tmp_pix = img1.getpixel((i,j))
        if (tmp_pix>127): 
            img1_k.append(1)
        else:
            img1_k.append(0)


img = Image.new('RGB', (img1_size[1],img1_size[0]), "white") 
cmap = {1: (255,255,255),
        0: (0,0,0)}
data = [cmap[i] for i in img1_k]
img.putdata(data)
img.show()             
img.save('Image2.png')

However, instead of original image:

The code produces rotated and inverted image:

I'm guessing that the format of putdata() differs from the way I acquired pixels for the list. How can I get the picture right?

falsetru · Accepted Answer · 2017-02-12 03:48:04Z

2

getpixel, putpixel is based on x-y coordinates while getdata, putdata is based on row-column based.

First, you need to make the img_k row-column based:

for j in range(img1_size[1]):     # row (y)
    for i in range(img1_size[0]): # column (x)
        tmp_pix = img1.getpixel((i,j))
        if tmp_pix > 127:
            img1_k.append(1)
        else:
            img1_k.append(0)

Second, you need to create x*y sized image:

img = Image.new('RGB', (img1_size[0], img1_size[1]), "white")  # <--
# OR  Image.new('RGB', img1.size, "white") 
cmap = {1: (255,255,255),
        0: (0,0,0)}
data = [cmap[i] for i in img1_k]
img.putdata(data)
img.show()             
img.save('Image2.png')

BTW, instead of mixing getpixel and putdata, by using getdata and putdata the code can be simpler:

from PIL import Image

img1 = Image.open('Image1.gif')
data = [(255, 255, 255) if pixel > 127 else (0, 0, 0) for pixel in img1.getdata()]
img = Image.new('RGB', img1.size, "white") 
img.putdata(data)
img.show()             
img.save('Image2.png')

edited Feb 12, 2017 at 3:48

answered Feb 12, 2017 at 3:44

falsetru

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1 Comment

falsetru Over a year ago

@CaiphasKain, You're welcome. Happy Python programming.

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