|
GIF/PNG
CoastWatch provides Internet browsable products in the GIF or PNG formats.
GIF uses a patented compression technique known as LZW and some software applications no longer
support the generation of these products. Therefore, PNG is used
as a replacement format which retains the 8-bit palette, uses a public compression scheme,
and is compatible with recent Internet browsers.
GIF and PNG images are commonly used graphic
formats compatible with many different types of software. These images are composed of a grid of pixels, which are each defined by a
number representing a color or shade of gray. The actual color that each value represents is defined by a color map associated with the
image.
GIF and PNG images are small and can be displayed directly in many software applications.
The images available from CoastWatch are 8-bit images, meaning that the number associated with each pixel is represented by a
binary code of eight characters, for example, 01100101. Because there are only 256 combinations of zeros and ones that can be represented
in eight bits, the pixel values of an 8-bit TIFF image are limited to integer numbers from 0 to 255. For this reason, data that contain
decimals, negative numbers, or values greater than 255 can not be represented directly in the GIF or PNG format.
|
|
