Scanned Raster Image Formats - GTX Compatible File Formats
GTX raster editing efficiency is greatly enhanced when the raster file is of the best quality. Consideration of the original scanned document's physical condition is a necessary first step. Some documents have dark backgrounds, and some have faint detail, and some have both. These are conditions which are best managed by applying approriate scanning parameters. As an example, the following scan, on the left, was done from a faint original document. That scan was performed without correct adjustment of the scanner's threshold parameter. The scan on the right was performed with a more suitable scanner threshold. The scan on the left, with it's loose assortment of pixel detail, would be of little use in a GTX editing session. GTX programs depend upon solid streams of pixel data which might be interpreted as lines, arcs, or circles.
Dithered Image
Better Image
Knowledge of image file formats is also valuable when creating a file from a scanned image for use in a GTX program. GTX requires the image to be bitonal. A bitonal image consists of one forground color and one background color. A non-bitonal, (color or grayscale), image may be opened in a GTX program but will be converted to bitonal before an editing session may proceed. The results of the bitonal conversion are seldom adequate. The following is an example of a scanned TIFF file, having true color attributes, which was processed through the bitonal conversion. During the removal of color detail many holes and pixel spikes were introduced. These scattered details may defeat the requirement for solid pixel streams upon which GTX programs depend.
 
An easy method for determining the quality of a scan is to view some detail, such as a text character, on the paper drawing using a magnification lense. What was seen under magnification should be an identical match to what is seen when the drawing is displayed while using the GTX program. This will require zooming in to the character that was observed on the paper.
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