In order to represent scanned data in the world coordinates SuperEdit uses a number of parameters that describe the scanned data and the original paper drawing. These parameters are:
raster size - scanned image size in pixels , also referred to as the width, and the number of lines;
resolution - image resolution equal to the scanner's resolution, if not changed by later processing, in dots/inch;
orientation - 90°, 180° or 270° rotation needed to position the scanned image properly on the screen;
scale - the nominal scale of the original drawing needed to determine the represented world size;
units - measuring units in which the world will be dimensioned;
insertion point - used to place the image in the coordinates system, so that the origin is properly defined, expressed in units.
In order to describe how these parameters are applied, let's use a simple notation [a x b] to denote a rectangle of dimensions a and b .
Raster size , i.e. the physical dimensions of the scanned image in pixels and lines , is known from the image file itself. Raster size and resolution are used to determine the original paper size in inches:
paper [width x length] = scan [pixels x lines] / resolution
Then, the orientation is used to position the image properly, so that it appears, as we want it on the screen:
for 0° and 180° : image [width x height] = paper [width x length]
for 90° and 270° : image [width x height] = paper [length x width]
The image dimensions are then converted to the corresponding world dimensions using the scale and units parameters:
world [width x height] = image [width x height] ∗ scale ∗ ( units / inch)
Finally, the origin of the coordinates system is established by defining the insertion point , i.e. the coordinates of the left lower corner of the image , as it appears after all the above transformations applied. This way, the above defined world width and height become the image 's extents in the world coordinates.