Is there a way to use Pillows “Image.convert()” on an existing variable?

Question

Hello,

maybe this question looks stupid, but I try to use Pillows Image.convert() to convert an image to grayscale. This image I have store

Answer 1

You can use

img = Image.fromarray(img)

to convert to a PIL Image type. From there, you should be able to use PIL's convert() function

img = img.convert('LA')

then, to access the pixel values directly you can either convert back to a numpy array

img_array = np.asarray(img)

or get pixel access to the PIL Image using

pixels = img.load()

Answer 2

Instead of saying Image.convert() use your image variable: img e.g img = img.convert('') and in this case:

img = img.convert('LA')

Answer 3

Whilst you could perfectly well convert your Numpy array to a PIL Image and then convert that to greyscale and then convert back to a Numpy array like this:

PILImage = Image.fromarray(Numpyimg)
PILgrey  = PILImage.convert('L')
Numpygrey= np.array(PILgrey)

You might as well just do the ITU-R 601-2 luma transform yourself, i.e.

L = 0.299 * Red + 0.587 * Green + 0.114 * Blue

So, you would get:

Numpygrey = np.dot(Numpyimg[...,:3], [0.299, 0.587, 0.114]).astype(np.uint8)