Chapter 6. Image Loading, Visual Effects, and Animation

Images are a central part of every game, and this chapter examines how we can (efficiently) load and display them, apply visual effects such as blurring, fading, and rotation, and animate them.

The ImagesTests application is shown in Figure 6-1. The screenshot includes the name of the images for ease of reference later.

Figure 6-1. ImagesTests and image names

An image name is the filename of the image, minus its extension.

The images (in GIF, JPEG, or PNG format) are loaded by my own ImagesLoader class from a JAR file containing the application and the images. The images are loaded using ImageIO's read( ), and stored as BufferedImage objects, to take advantage of the JVM's "managed image" features.

ImagesLoader can load individual images, image strips, and multiple image files that represent an animation sequence.

The animation effects utilized by ImagesTests fall into two categories:

• Those defined by repeatedly applying a visual effect, such as blurring, to the same image but by an increasing amount

• Those where the animation is represented by a series of different images displayed one after another

Table 6-1 lists the image names against the visual effect they demonstrate.

Table 6-1. Images names and their visual effects

Image name	Visual effect
atomic	Rotation
balls basn6a08	Mixed colors
bee	Teleportation (uneven fading)
cheese	Horizontal/vertical flipping
eyeChart	Progressive blurring
house	Reddening
pumpkin	Zapping (red/yellow pixels)
scooter	Brightening
ufo	Fading
owl	Negation
basn6a16	Resizing
cars	Numbered animation
kaboom
cats
figure
fighter	Named animation
numbers	Callback animation

The effects are mostly implemented with Java 2D operations, such as convolution or affine transformation. Occasionally, I make use of capabilities in drawImage( ), e.g., for resizing and flipping an image.

The majority of the images are GIFs with a transparent background; balls.jpg is the only JPEG. The PNG files are: owl.png, pumpkin.png, basn6a08.png, and basn6a16.png. The latter two use translucency, and come from the PNG suite maintained by Willem van Schaik at http://www.schaik.com/pngsuite/pngsuite.html.

I've utilized several images from the excellent SpriteLib sprite library by Ari Feldman, available at http://www.arifeldman.com/games/spritelib.html, notably for the cats, kaboom, cars, and fighter animations.

The application code for this chapter can be found in the ImagesTests/ directory.