Picture and Image

There are two types you can use to create pictures: Picture and Image.

This section describes how to use and how to choose between them.

Choosing Between Picture and Image

If you're new to Scala, Image is probably the best choice for you. It's written in a simple style, so you will have an easier time understanding how to use it and any error messages that may arise.

If you're a more experienced Scala user you could choose Picture. It allows access to platform specific features not available on Image.

Using Image

To use Image we need the following imports:

import doodle.core.*
import doodle.image.*

import doodle.image.syntax.all.*

We'll also need to import a backend. Most people will be working on the JVM, and will use the Java2D backend.

import doodle.java2d.*
import cats.effect.unsafe.implicits.global

Image is based on composition and the interpreter pattern.

Composition basically means that we build big images out of small images. For example, if we have an image describing a red square and an image describing a blue square

val redSquare = Image.square(100).fillColor(Color.red)
val blueSquare = Image.square(100).fillColor(Color.blue)

we can create an image describing a red square next to a blue square by combining or composing them together.

val composition = redSquare.beside(blueSquare)

When draw this has the output shown below.

The interpreter pattern means that we separate describing the Image from rendering it. Writing Image.square(100) doesn't draw anything. To draw an image we need to call the draw() method. This separation is important for composition; if we were to immediately draw we would lose composition.

Using Picture

To use Picture we need the following imports:

import doodle.core.*
import doodle.syntax.all.*

We'll also need to import a backend. Most people will be working on the JVM, and will use the Java2D backend.

import doodle.java2d.*

import cats.effect.unsafe.implicits.global

Picture works the same way as Image, using composition and the interpreter pattern. In fact the above example can be rewritten using picture by simply changing Image to Picture.

val redSquare = Picture.square(100).fillColor(Color.red)
val blueSquare = Picture.square(100).fillColor(Color.blue)
val composition = redSquare.beside(blueSquare)

To draw the Picture we call the draw() exactly as we would with Image.

Shapes→