Scanning to a raster data format

Scanners generate raster data when a document is scanned. The contents of the document are represented as a matrix of black and white dots. The individual dots are not logically related as such. The dots represent the contents of the document as a kind of digital photo based on computer data.

The number of dots (pixels) per unit of lenght is set as a resolution value specified in dpi (dots per inch); the arrangement of the pixels in the matrix are described with different raster formats (TIFF, RCL, JPG, BMP, etc.). The file format generated is based on the end use of the digital image.

Our equipment scans at 200dpi and 400dpi. A 200dpi scan is best suited for viewing on a computer screen, but may not print at an acceptable quality. A 400dpi scan is a good resolution for printing, but also generates a larger file. If you are unsure what dpi your documents should be scanned at, give us a call and we will discuss in more detail what your expected results are.

Raster to vector conversion

Vector data represents geometric elements such as lines, circles, arcs, text, etc. These are the basic elements used to create all other types of elements in CADD drawings. In addition, vector elements can also be picked, moved, scaled, deleted or copied easily.

In short, a raster image is picture of your desk; whereas a vector file is your
desk.

With the use of scanner technology, manually created drawings are easy to render as digital data, but the raster files created are only of real use in CADD programs once they have been converted to vector data.

Raster-to-vector conversion (vectorization) involves a process of interpretation in which the raster image is described with, and replaced by, vector elements. If the original document contains clear and unambiguous structures, then the process will be successful. Unclear areas in the original produced by the effects of age, weathering and imperfect manual preparation will lead to raster structures that can only be converted inaccurately. By using comparison and approximations however, it is still possible to generate the most probable vector representation. Once the vectorization is complete, the contents of the raster file are available in vector form. These contents are exported to a standard data exchange format (DXF) and can read into almost any CADD program.

Common applications

Minimum scan size (document): 4.25" x 4.25"
Maximum scan size (document): 36" x 240"
Minimum scan resolution: 200dpi
Maximum scan resolution: 400dpi
Standard raster format: TIFF (Group 4 Compression)
Standard vector format: DXF (Drawing Exchange Format)