Exercise

# Detect edges (2)

Edge detection can be performed along multiple axes, then combined into a single edge value. For 2D images, the horizontal and vertical "edge maps" can be combined using the Pythagorean theorem:

$$z = \sqrt{x^2 + y^2}$$

One popular edge detector is the Sobel filter. The Sobel filter provides extra weight to the center pixels of the detector:

```
weights = [[ 1, 2, 1],
[ 0, 0, 0],
[-1, -2, -1]]
```

For this exercise, improve upon your previous detection effort by merging the results of two Sobel-filtered images into a composite edge map.

Instructions

**100 XP**

- Apply
`ndi.sobel()`

to`im`

along the first and second axes. - Calculate the overall edge magnitude using the Pythagorean theorem. Use
`np.sqrt()`

and`np.square()`

. - Display the magnitude image. Use a grayscale colormap and set
`vmax`

to`75`

.