[JAVA][Beginning Java 8 Games Development]

Chapter 5 ■ An Introduction to Game Design: Concepts, Multimedia, and Using Scene Builder
Also, note that you can set the percentage of dithering that is used. I often select either the 0 percent or
100 percent setting; however, you can fine-tune the dithering effect anywhere between these two extreme values.
You can also choose between dithering algorithms, because, as you probably have surmised, the dithering effect is
created using dithering algorithms, which are part of the indexed file format (in this case, PNG8) compression routines.
I use diffusion dithering, which gives a smooth effect along irregularly shaped gradients, as is seen in the car
fender. You can also use a noise option, which is more randomized, or a pattern option, which is less so. The diffusion
option usually gives the best results, which is why I choose it when I am using indexed color (which is not often).
Dithering, as you might imagine, adds data patterns to an image that are more difficult to compress. This is
because smooth areas in an image, such as gradients, are easier for the compression algorithm to compress than
sharp transitions (edges) or random pixel patterns (e.g., dithering or “noise” from a camera CCD).
Therefore, applying the dithering option will always increase the data footprint by a few percentage points. Be
sure to check the resulting file size with and without dithering applied (selected in the Export dialog) to see if it is
worth the improved visual result that it affords. Note that there is also a transparency option (check box) for indexed
color PNG images but that the alpha channel used in PNG8 images is only 1 bit (on/off), not 8 bit, as with PNG32.
You can also increase the data footprint of your image by adding an alpha channel to define transparency for
compositing. This is because by adding an alpha channel you will be adding in another 8-bit color channel (or a
transparency channel, actually) to the image being compressed. If you need an alpha channel to define transparency
for your image to support future compositing requirements, such as using the image as a game sprite, there is not
much choice but to include the alpha channel data.
If your alpha channel contains all zeroes (or uses an all-black fill color), which would define your imagery as
being completely transparent, or contains all FF values (or uses an all-white fill color), which would define your image
as being completely opaque, you would essentially (in practical terms) be defining an alpha that does not contain any
useful alpha data values. The transparent image would therefore need to be removed, and the opaque image would
need to be defined as a PNG24 rather than a PNG32.
Finally, most alpha channels that are used to mask objects in the RGB layers of the digital image should compress
very well. This is because the alpha channel is primarily areas of white (opaque) and black (transparent), with some
medium-gray values along the edge between the two colors to antialias the mask (see Figure 5-2). These gray areas
contain the antialiasing values in the alpha channel, and will provide the visually smooth-edge transitions between
the object in the RGB layers of the image and any background color or background images that may be used behind it.
The reason for this is that in the alpha channel image mask, an 8-bit transparency gradient (from white to
black) defines levels of transparency, which could be thought of as per-pixel blending (opacity) strength. Therefore,
the medium-gray values on the edges of each object in the mask (which is contained in the alpha channel) will serve
essentially to average the colors of the object edge, and any target background, no matter what color (or image) value
it may contain. This offers real-time antialiasing with any target background that may be used, including animated
backgrounds.
Digital Video and Animation: Frames, Rate, Looping, Direction
Interestingly, all the concepts that I have just covered for digital images apply equally well to digital video and
animation, as both formats use digital images as the foundation for their content. Digital video and animation extend
digital imaging into the fourth dimension (time) by using frames. The two formats are composed of an ordered
sequence of frames, which are displayed rapidly over time.
The term “frame” comes from the film industry, in which, even today, frames of film are run through film
projectors at a rate of 24 frames per second (24FPS), which creates the illusion of motion. Because both digital video
and animation are made up of a collection of frames containing digital images, the concept of frame rate, expressed
as frames per second, is also very important when it comes to the memory data footprint optimization work process
(for animation assets) as well as the digital video file size data footprint optimization work process. As discussed
previously, in JavaFX this attribute for animation is stored in the Animation object rate variable (see Chapter 4).
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