[JAVA][Beginning Java 8 Games Development]

Chapter 5 ■ An Introduction to Game Design: Concepts, Multimedia, and Using Scene Builder
There are 256 levels of brightness for each red, green, and blue color value that is held for each pixel. This allows
you to set 8 bits of value-controlling color brightness variation for each of the red, green, and blue values, from a
minimum of 0 (#00, or off, all dark, or black) to a maximum of 255 (#FF, or fully on, maximum color contributed). The
number of bits that are used to represent digital image pixel color is referred to as the color depth of the image.
Common color depths used in the digital imaging industry include 8 bit, 16 bit, 24 bit and 32 bit. I will outline
these here, along with their formats. The lowest color depth exists in 8-bit indexed color images. These feature a
maximum of 256 color values and use GIF and PNG8 image formats to hold this indexed color type of data.
A medium color depth image will feature a 16-bit color depth and will thus contain 65,536 colors (calculated as
256 × 256). It is supported by the TARGA (TGA) and tagged image file format (TIFF) digital image formats. If you want to
use digital image formats other than GIF, JPEG, and PNG in your Java 8 games, import the third-party ImageJ library.
Truecolor color depth images will feature 24-bit color depth and will thus contain more than 16 million
colors. This is calculated as 256 × 256 × 256, which yields 16,777,216 colors. File formats supporting 24-bit color
depth include JPEG (or JPG), PNG, BMP, XCF, PSD, TGA, TIFF, and WebP. JavaFX supports three of these: JPG,
PNG24 (24 bit), and PNG32 (32 bit). Using 24-bit color depth will give you the highest quality level. This is why I am
recommending the use of PNG24 or PNG32 for your Java games. Next, let’s take a look at how to represent image pixel
transparency values through alpha channels and how these can be used for compositing digital imagery in real time
in Java 8 games!
Digital Image Compositing: Using Alpha Channels and Transparency in Layers
Compositing is the process of seamlessly blending together multiple layers of digital imagery. As you might imagine,
this is an extremely important concept for game design and development. Compositing is useful when you want to
create an image on the display that appears as though it is one single image (or animation), when it is actually the
seamless collection of two or more composited image layers. One of the principle reasons you would want to set up
an image or animation composite is to allow programmatic control over various elements in those images, by having
them on different layers.
To accomplish this, you need to have an alpha channel transparency value, which you can use to control the
precision of the blending amount of a given pixel with another pixel (in the same x, y image location) on other layers
(above and below it).
Like the other RGB channels, an alpha channel has 256 transparency levels. In Java programming the alpha
channel is represented by the first two slots in a hexadecimal representation of #AARRGGBB data values (which I
will be covering in detail in the next section). Alpha channel ARGB data values use eight slots (32 bit) of data rather
than the six data slots (#RRGGBB) used in a 24-bit image, which is really a 32-bit image with zero alpha channel data.
Therefore, a 24-bit (PNG24) image has no alpha channel and will not be used for compositing, unless it is the
bottom image plate in a compositing layer stack. In contrast, PNG32 images will be used as compositing layers on
top of PNG24 (background plate) or PNG32 (lower, z-order compositing layers), which will need this alpha channel
capability to show through (via alpha channel transparency values) in certain pixel locations in the image composite.
How do digital image alpha channels, and the concept of image compositing, factor into Java game design? The
primary advantage is an ability to break the game play screen, and the sprites, projectiles, and background graphic
elements that it includes, into a number of component layers. The reason for doing this is to be able to apply Java 8
programming logic (or JavaFX classes) to individual graphic image elements to control parts of your game play screen
that you would not otherwise be able to control individually were it one single image.
Another part of image compositing, called blending modes, also factors heavily into professional imagecompositing
capabilities. JavaFX blending modes are applied by using the Blend class with the BlendMode constant
values found in the javafx.scene.effect subpackage (see Chapter 4). This JavaFX blending effect package gives
Java game developers many of the same image-compositing modes that Photoshop (and GIMP) afford to a digital
imaging artisan. This turns Java 8 (via JavaFX) into a powerful image-compositing engine, just like Photoshop, and
the blending algorithms are controllable at a very flexible level, using custom Java 8 code. JavaFX blending mode
constants include ADD, SCREEN, OVERLAY, DARKEN, LIGHTEN, MULTIPLY, DIFFERENCE, EXCLUSION,
SRC_ATOP, SRC_OVER, SOFT_LIGHT, HARD_LIGHT, COLOR_BURN, and COLOR_DODGE.
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