Steve Plummer posted detailed lessons about drawing up illusion charts on his website.
But everyone does everything as it convenient to themselves.
And I have some practice, which I want to share with you.

Choose the picture

Let it be a bunny for baby plaid. Then reduce the image.
Take care that the reduction doesn’t harm. Otherwise, you will not be able to knit the details.
In our case 150 X 112 is the best option.

Some secrets

I almost don’t know how to work in Photoshop. I don’t even know how to make a grid there. The program, which Steve advises, don’t want to work steadily for some reason on my PC.

So I took the free software for cross stitch charting EmbroBox.
Let’s load the bunny there and save the scheme.

Now you can open the resulting diagram in Photoshop and work.
The advantage of my method is that you can see the final image right away.

Bunny will be seen from the side. Therefore, turn the image.
Create a new layer. Color opacity is 50%. Denote the rows of the picture. Later it will help you to draw and knit.

Create one more layer. Now we need to draw a stitch pattern. Set color opacity 100% and then just paint over ALL not white squares on the rows of picture.

The result is such a semi-finished product

Create a new layer. Draw the background.
Here is the secret again.
Now you should paint black the darkest squares.

Мы будем черным закрашивать самые темные квадратики.

Again, the secret.
Paint the squares only if they are under the painted stitches of the picture.

The bunny starts to appear.

To see more details download the photoshop template
Try to finish the bunny by yourself.