Prepare Images For CNN
How are images looked at by computers?
Matrices
Number in matrix represents darkness of image in that position (darker part → larger #)
How are coloured images looked at by computers?
Matrices, but with extra dimension (RGB)
Stack of 3 matrices
Reshaping Numpy Arrays
# images is a list of floats/integers that represent an image
images = np.array(images, dtype = 'float')
We have a numpy array (
images
) of these dimensions:(x, )
Need 4D array for input shape whose product is
So we can take and reshape as:
np.reshape(-1, sqrt(x), sqrt(x), 1) # 1 if the image is greyscaled
Plotting Images as Numpy Arrays
import matplotlib.pyplot as plt
plt.imshow(images_reshaped[0].reshape(sqrt(x),sqrt(x)),cmap='gray')
plt.show()
Creating Labels with Numpy Arrays
# Isolate dataframe to only have the labels
y = []
for i in range(len(df)):
y.append(np.array([labels_df.iloc[i,:]], dtype='float'))
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