Lesson 1 of 4

Image basics

Watch, read the card, then practise. Pixels and channels · Preparing images

Video coming soon

The video for this lesson is being recorded.

Meanwhile, the notes below and the 60-second cards cover the same ideas.

Pixels and channels
An image is a grid of pixels. A colour image has 3 channels (red, green, blue), each 0 to 255.
Remember: Height comes first in the shape, then width.
Preparing images
Before training, images are resized to one size and their pixel values scaled.
Remember: Prepare images at prediction time exactly as in training.

Try the example in Code Lab

import numpy as np
img = np.zeros((224, 224, 3), dtype=np.uint8)
print(img.shape, img.size)

Lesson 1 of 4

Watch, read the card, then practise. Pixels and channels · Preparing images

Video coming soon

The video for this lesson is being recorded.

Meanwhile, the notes below and the 60-second cards cover the same ideas.

Pixels and channels
An image is a grid of pixels. A colour image has 3 channels (red, green, blue), each 0 to 255.
Remember: Height comes first in the shape, then width.
Preparing images
Before training, images are resized to one size and their pixel values scaled.
Remember: Prepare images at prediction time exactly as in training.

import numpy as np
img = np.zeros((224, 224, 3), dtype=np.uint8)
print(img.shape, img.size)