Drawing in Scratch

We have already drawn a background for a Scratch program a few times. Now we make our own Scratch program, in which you can draw!

You can find an example below.

You learn to:

use the pen
clear the background
change the color of the pen
change the thickness of the pen
change the appearance of a variable

STEP 1.

We start with creating the pencil as a sprite. You can also find the pencil used above in the library.

We want the pencil to follow our mouse pointer. We haven't done this yet, but you will probably find the right block!

Which block should I use?

Do you combine this block with the correct other blocks?

Hint!

You will notice that the program does not work quite the way we want. We have to make sure that the point of the pencil goes to our mouse pointer. For this we need to change the center of the sprite.

You do this by clicking on the button "Center of appearance".

Now we want to draw with the pen! As long as you click your mouse, we want it to be drawn.

You can find all the cubes around the drawing in the group "Pen". To do this, you can first click on an "Extension".

After which you have the choice for the pen:

We will now need the following two blocks:

Try to write the program now!

How to start?

Insert appropriate blocks into an "if ... then ... else ..." block.

How do I know when the mouse button is pressed?

Use this block:

Possible solution?

STEP 2: a second color.

We now want to be able to switch between two colors, choose two yourself! You will need to do the following:

Create two sprites, be sure to choose your own colors! You can click on this to change color. We made 'Blue' and 'Green'.
Allow the pencil to change color. So you will have to create different costumes.
Changing the pen color, are you looking for the right block for this?

How do I change the pen color?

Use this block:

Extra hint!

When you click on the sprite 'Green', a signal should be sent to the pencil sprite.

Solution

At the sprite 'Green' we put:

At the pencil sprite we put:

STEP 3: erase.

It is now quite annoying that your attempts remain. You can also clear the screen.

Do you provide a sprite that can clear the screen? It can also be useful to clear the screen when you start the program.

How do I clear the screen?

Hint!

Again, you will have to send a signal to the pencil sprite.

To clear the screen at the start of the program, insert the block below the starting block

Now we can only wipe the entire screen. We also want to be able to erase a small part of a drawing. Do you provide an eraser?

What do I have to create?

Make sure to create a new sprite and a new look for your pencil sprite. You decide how this looks like.

How do I delete a small part of a drawing?

Change the color of the pen to white:

STEP 4: Pen width.

Now we want to be able to determine the thickness of our pen. For this you will have to create a variable.

Do you look for how to change the thickness of the pen yourself?

With which block do I change the thickness?

Now make sure that the thickness of the pen is always equal to your variable.

Where to put this block?

This should be in the repeat block of your pen:

We want to determine the thickness using a slider. You can do this by right-clicking on the display of your variable. Then click on 'Slide'.

STEP 5.

We now want to make our program completely perfect!

You may have noticed that you can also draw with the colors and eraser on the sprites. This doesn't look very nice. We want you to be able to draw only under our sprites.

So you will have to adjust the condition for your "if ... then ... else ..." block that you made in step 1. We want to add an extra condition. This can be done with the "and" block:

What condition should I add?

Your mouse pointer should not be too high. What value does this say something about? About x or y?

Extra hint:

You insert the next block into the "and" block. Of course, the value may differ depending on your drawing.

Solution

You get

(a) Can you add some extra colors? To make it easier for yourself, you can copy an existing sprite.

(b) Can you insert some keyboard shortcuts? For example, you could clear the screen when you press the 'w' key.

(c) You may have already seen the "pen brightness" box. With this you can make your color darker and lighter. Are you creating a new slider that uses this?

Download the code.

solution draw in Scratch