Options when importing a nongeoreferenced image file

Calibration in the Image Calibration pane uses an IlvFittedTransform class. This class requires a certain number of points to be entered for more complex transformations (that is, a higher degree of interpolation).

You must enter:

Polynomial interpolations are more precise in the area inside the calibration points. If you use this feature, try providing calibration points that cover as large an area as possible.

The first part of the following figure shows an initial map of Alaska. Calibration points have been placed around the right side of this image. The second part of the following figure shows the interpolated image, however, the left side is quite skewed.

World files provide information for image calibration. A World file has the same filename as the main image file. For example, a file called USA.jgw could accompany an image named USA.jpg , and contain the coordinates of the image in seconds of arc.

An example of a World file content is as follows:

1.50000000000000 (X pixel size) 
0.00000000000000 (translation) 
0.00000000000000 (rotation) 
-1.50000000000000 (Y pixel size) 
1934001.50000000000000 (X coordinate of the upper left pixel)
1187698.50000000000000 (Y coordinate of the upper left pixel)

The Map Builder ignores the translation and rotation parameters.

When loading images in GIF, JPG, PNG, or TIF format, the Map Builder scans the directory to see if a World file exists, and if so, predefines the image bounds accordingly in the importation dialog box.

For GIF, JPG, PNG, and TIF formats, the world file extensions checked are in the form .tifw or .tfw , .gifw or .gfw , .jpgw or .jgw , and .pngw or .pgw respectively.