Transcript Slide 1

GRAPHICAL DATA
EXCHANGE FORMATS
Graphics Interchange Format (.GIF)
Graphics Interchange Format (.GIF)
768 Byte Indexed Color Table
Contains RGB Values for
256 Colors or Gray Tones
Graphics Interchange Format (.GIF)
Choosing the Correct
Pixel Density is Important
for Maintaining Image Quality
Joint Photographic Experts Group (.JPG)
File Format
Joint Photographic Experts Group (.JPG)
File Format
Data are Compressed using a
“Lossy" Method where
Some Data are Lost
Joint Photographic Experts Group (.JPG)
File Format
Joint Photographic Experts Group (.JPG)
File Format
Tagged Image
File Format
(.tif or .tiff)
TIFF Advantages
• Flexible and adaptable file format.
• Can have multiple images and data in a
single file through the inclusion of "tags" in
the file header.
• Tags indicate the basic geometry of the
image, such as its size, or if one of several
image compression options are used.
TIFF World
File --GEOTIFF
(.tfw)
ESRI TIFF World File – 6 ASCII Lines
1. Horizontal distance in meters represented by
each pixel.
2. Rotation angle about the y axis.
3. Rotation angle about the x axis.
4. Vertical distance in meters represented by each
pixel. Normally negative because an image has
its origin in the top left corner.
5. Easting coord. of the center of the top left pixel.
6. Northing coord. of the center of the top left pixel.
TFW File Example
0.6
0
0
-0.6
355000.317
459999.682
Sometimes will have two additional lines:
1. Grid zone or coordinate system
2. Datum