354 CHAPTER 10: Android Animation: Making Your UI Designs Move
Frame Animation Concepts and Techniques
The first thing that we will always need to do is to get our “knowledge foundation” regarding frame
animation’s concepts, formats, and terminology, since we’re going to use these during the rest of
this chapter, in conjunction with working with Android animation. This new media type is commonly
called 2D animation, and I’m going to cover 2D vector animation, also known as procedural
animation or “tween” animation, later on in this chapter.
Frame Animation: Cels, Frames, and Terminology
Frame-based animation could be termed “cel-based” animation because of the original 2D
animation created by Walt Disney. Disney animators drew on what at that time were called “cels,”
in order to represent each individual movement in their cartoon animation in its own cel. Interestingly,
the original cels from these animation projects are now “framed,” and sold to collectors for
thousands of dollars! Thus, there are both physical and conceptual connections between these two
animation terms, frame animation and cel animation.
Later on, with the advent of feature films, the term “frame” replaced the term “cel.” This was
because the analog film projectors which were used to display 24 frames per second used frames
of film. These frames of film were displayed using one or more reels containing film frames, which
would create the illusion of motion when light was projected through the moving frames using film
projectors in a theater projection room behind an audience.
The technical term for digital frame-based animation is raster animation, as the frames or cels are
made up of collections of pixels. Pixel-based imagery is commonly known in the industry as raster
imagery. Raster images are also commonly called “bitmaps” because they are a map (array) of
bits (pixels). In fact, there is the bitmap (.BMP) file format used in Microsoft Windows; however, this
digital image file format is not currently supported for use under the Android OS. Because the bitmap
file format has become so popular due to its use in Windows, raster animation is also frequently
called bitmap animation within the multimedia production industry. Android has a BitmapDrawable
class and creates a BitmapDrawable object for your bitmap image assets.
We will utilize these various animation industry terms interchangeably throughout this chapter, so
that you will get used to using all of these different, but accurate, terms to refer to your frame-based
2D animation, which can also be called raster animation, bitmap animation, frame animation, cel
animation, and digital image animation.
Frame Animation Formats: PNG, GIF, JPEG & WebP
The Android OS supports the same open source digital image file formats which you use for 2D
imagery in the Android application for use within your frame-based animation assets. If you think
about it, this is quite logical, as a 2D animation is defined by using those individual 2D digital image
frames as the foundation for 4D motion.
The significance of this is that you can use indexed color images if you want to create an 8-bit frame
animation, using the PNG8 or GIF formats. You can also use truecolor image formats to create your
24-bit, or 32-bit, frame animation. You would do this by using the PNG24, PNG32, WebP, or the
JPEG digital image file formats.