how can I conver a dataset like mnist fom RGB to gray scale

Question

Hello there I'm trying to convert the MNIST dataset to greyscale with python but I can not do it right.

code:

(x_train, y_train), (x_test, y_test) = mnist.load_data() 
x_train = x_train.reshape(60000, 28, 28, 1)
x_test = x_test.reshape(10000, 28, 28, 1)

When I enter the above I get this error:

TypeError: Invalid shape (28, 28, 1) for image data

What am I doing wrong?

The reshape method would not 'aggregate' the data. See if this helps: https://stackoverflow.com/questions/41971663/use-numpy-to-convert-rgb-pixel-array-into-grayscale — HasnainMamdani, Mar 18 '20 at 18:58
Thanks, but i didn't get the answer. Can I apply np.dot() on dataset to convert it to gray scale? — Sahar Metwally, Mar 18 '20 at 19:18
Yes exactly, you choose the ratios of RGB you want to use for conversion. Although I'm surprised you need to do this because MNIST data usually already comes in grayscale. Perhaps also check your original data dimensions and mention the source you're obtaining the MNIST data from. — HasnainMamdani, Mar 18 '20 at 19:51
Thanks a lot for your reply. I used keras to load MNIST dataset. — Sahar Metwally, Mar 18 '20 at 20:20
A comprehensive list of solutions can be found here: https://stackoverflow.com/questions/12201577/how-can-i-convert-an-rgb-image-into-grayscale-in-python — AthulMuralidhar, Mar 18 '20 at 20:34
The error you posted does not come from `reshape`. Please post the _full_ error traceback. I assume you get this error when trying to plot images, e.g. via `matplotlib`'s `imshow`. In that case, you simply have to remove the last dimension. — xdurch0, Mar 18 '20 at 23:14

score 1 · Answer 1 · answered Mar 18 '20 at 20:36

Easiest way is to use Pillow like so:

In [27]: from PIL import Image                                                                                                                        
In [28]: img = Image.open('test.jpg').convert('L') 
    ...: img.save('greyscale.jpg')

how can I conver a dataset like mnist fom RGB to gray scale

1 Answers1