Game Development Reference
In-Depth Information
images. The GIF format supports animation and is still widely used to provide
image animation effects. It also uses a lossless compression that is more ef-
fective when large areas have a single color, and ineffective for detailed im-
ages or dithered images.
•
BMP
: This file format (Windows bitmap) handles graphics files within the Mi-
crosoft Windows OS. Typically, the BMP files are uncompressed, hence they
are large; the advantage is their simplicity and wide acceptance in Windows
programs.
•
Portable Network Graphics
(
PNG
): This file format was created as the free,
open-source successor to GIF. The PNG file format supports 8-bit paletted
images (with optional transparency for all palette colors) and 24-bit true-color
(16 million colors) or 48-bit true-color with and without alpha channel; while
GIF supports only 256 colors and a single transparent color. Compared to
JPEG, PNG excels when the image has large, uniformly colored areas. Thus
lossless PNG format is best suited for pictures still under edition, and the
lossy formats, such as JPEG, are best for the final distribution of photograph-
ic images, because in this case, the JPG files are usually smaller than the
PNG files.
PNG provides a patent-free replacement for GIF and can also replace many
common uses of TIFF. Indexed-color, grayscale, and true-color images are
supported, plus an optional alpha channel.
PNG is designed to work well in online viewing applications, such as web
browsers, so it is fully stream able with a progressive display option. PNG is
robust, providing both full-file integrity checking and simple detection of com-
mon transmission errors. Also, PNG can store gamma and chromaticity data
for improved color matching on heterogeneous platforms. For more details
Vector graphics
As opposed to the raster image formats discussed previously (where the data de-
scribes the characteristics of each individual pixel), vector image formats contain a
geometric description which can be rendered smoothly at any desired display size.
At some point, all vector graphics must be rasterized in order to be displayed on di-
gital monitors. However, vector images can be displayed with analog CRT techno-
