306 CHAPTER 9: Android Graphic Design: Making Your UI Designs Visual
These hexadecimal data slots represent the RGB values in the following format: #RRGGBB.
Thus, for the color white, all red, green, and blue channels in this hexadecimal color data value
representation are at the maximum luminosity of fully on, or FF, which would be 16 times 16, or the
full 256 data value for each RGB color channel. For this reason, the value #FFFFFF would represent
the whitest white that is possible.
Note As you can see, I’m giving you all of the different industry terminology (color channel, color plane,
color plate) that you will find currently being used in the graphics industry. All of these terms are used
interchangeably.When you “additively” sum all of these RGB colors together, you will get white light. As I have
mentioned before, the color yellow is represented by the red and green channels being on and the
blue channel being off, so the hexadecimal notation representation for the color yellow would be
#FFFF00, where both red and green channel slots are on, using FF for a color intensity (level) value
of 256, and the blue channel slots are fully off using 00, a zero value.
As I mentioned earlier in this section, there is also a 32-bit image color depth whose data values are
represented using the ARGB color channel model, where the A stands for alpha, which is short for
alpha channel. We’ll be going over the concept of image alpha and alpha channels in far greater
detail during the next section of the chapter on alpha channels, and we will also cover the related
concept of pixel blending. Let’s get more advanced in Android graphic design so we can make our
applications truly stand out!
The hexadecimal notation data slots for an ARGB color channel model data values will hold data
in the following format: #AARRGGBB. Thus, to represent the fully opaque color white, all alpha,
red, green, and blue channels in this hexadecimal color data value representation would be at a
maximum luminosity (as well as opacity), and the alpha channel fully opaque, as represented by an
FF value, so its hexadecimal value would be: #FFFFFFFF.
A 100% transparent alpha channel is represented by the alpha channel slots being set to zero;
thus, a fully transparent image pixel could be #00FFFFFF, or #00000000. It is important to
notice that if an image alpha channel is set to be fully transparent, then each pixel’s color value
(represented by the last six hexadecimal data slot values) does not even matter, and thus you could
put any color value in these last six data slots!
Image Compositing Transparency: Alpha Channels
In this section of the chapter, we’ll take a look at how digital images are composited together, which
is a process known as image compositing, which is usually done by a professional who is called a
digital image compositor.
Digital image compositing is the process of blending together more than one layer of digital
imagery, in order to obtain the resulting image. A composite image on a display screen will appear
as though it is one single image, when in fact, it is actually a collection (a “stack”) of more than one
seamlessly composited digital image layers.