How can I use a pre-trained neural network with grayscale images?

Question

I have a dataset containing grayscale images and I want to train a state-of-the-art CNN on them. I\'d very much like to fine-tune a pre-trained model (like the ones here).

Answer 1

A simple way to do this is to add a convolution layer before the base model and then feed the output to the base model. Like this:

from keras.models import Model
from keras.layers import Input 

resnet = Resnet50(weights='imagenet',include_top= 'TRUE') 

input_tensor = Input(shape=(IMG_SIZE,IMG_SIZE,1) )
x = Conv2D(3,(3,3),padding='same')(input_tensor)    # x has a dimension of (IMG_SIZE,IMG_SIZE,3)
out = resnet (x) 

model = Model(inputs=input_tensor,outputs=out)