World files are plain text files used along side a normal image file. The world file tells a GIS program how to render the image. The filename is the same as the main image, with a different extension:
| actual image file | world file extension |
|---|---|
| jpg | jgw |
| tif | tfw |
The contents of a world file consist of six lines, as shown in the following example:
| line # | example value | description |
|---|---|---|
| 1 | 0.17578125 | x-scale value |
| 2 | 0 | y rotation/skew |
| 3 | 0 | x rotation/skew |
| 4 | -0.17578125 | y-scale value * I think this always needs to be negative |
| 5 | -180 | top-left x coordinate |
| 6 | 90 | top-left y coordinate |
* Note that the coordinates need to be in the units of the actual projection of the image