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Video Game Design Foundations
Video games are a visual media. Much of the experience of playing a video
game involves the images the player sees on screen. There are two basic types
of images: raster and vector. In addition, images may be compressed to save
storage space.
Raster Images
The most common type of images used in 2D video games are raster
images.
Raster images
are images that are made of dots or pixels. Each pixel
in the image has a specific color and location to construct the final image. A
raster image is called a
bitmap
because the location and color of each pixel is
mapped. The computer reads a bitmap image by creating a coordinate grid with
the origin at the top-left corner and increasing the X value moving right and
the Y value moving down. In each space of the coordinate grid is a single pixel.
A pixel can only be one color. To determine the color of a pixel at a particular
coordinate location, the color value of a pixel is read by the computer and
displayed.
Originally, bitmaps were only made at a bit depth of 1.
Bit depth
is a
binary measurement for color. Binary allows for only two values, either a 1
or a 0. A bit depth of 1 describes the exponent value of the binary digit. A
bit depth of 1 means 21. A bitmap value of 1 would, therefore, assign a white
pixel on the coordinate grid where required. This produces a black and white
image with no gray.
Eventually, computers were able to read bitmaps to a bit depth of 4. A
bit depth of 4 allowed for a total of 16 colors, as 24 equals 16. The modern
minimum standard for computer-displayed color is a bit depth of 8 or higher. A
bit depth of 8, or 28, allows for 256 colors. Two hundred fifty-six–color devices
are typically handheld devices where graphic quality is not needed. Computer
monitors, HDTVs, and other devices that require quality graphics try to achieve
true color or deep color.
True color
has a bit depth of 24. True color uses the familiar RGB color
model with 256 shades of red, 256 shades of green, and 256 shades of blue.
True color produces 224 colors, or 16,777,216 colors. Since the human eye is
only capable of discriminating a little more than 10 million colors, 24-bit color
can result in more colors than
the human eye can see. Other
color depths above 24 bit fall into
the deep color range.
Deep color
is supported by Windows 7 up
to a 48-bit depth. This provides
more intense colors and shadow.
Deep color can produce a
gamut
of over 1 billion.
Bit depth also allows for transparency. With a large gamut of color, an alpha
channel can be allocated. Alpha channel varies the opacity of the color. The
alpha channel
can support from full transparency all the way to full opacity. A
16-bit alpha channel can support 65,536 values of transparency.
Images
CHEAT CODE: GAMUT
Gamut is a range or series. A gamut
of color is the entire range of colors.