Scan2CAD raster to vector conversion software

REVIEW:

Contex sd large format scanner

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Scanning in Greyscale

CAD users will not normally need to scan in greyscale, however we mention it briefly here out of interest.

In our review of the Graphtec CSX300 we noted that by default, the CSX300 scans monochrome images using its green LED only (greenscale), but that it includes a Gray Balance option that allows it to scan monochrome using red, green and blue LEDs.

If you look at the SD4490 scans below, you can see that the green and red threads look as though they are the same colour in the greyscale image. This indicates that like the CSX300 in default mode, the SD4490 is scanning monochrome in greenscale. This can affect the way that images are thresholded to black and white.

For more details, see our Graphtec CSX300 review.

Scanning in Colour

Contex does not recommend its SD series large format scanners to users who require high quality colour scans of artwork, photographs and the like. For these types of application, Contex recommend their HD series scanners, which use CCD technology.

However, the SD series' colour capability is more than adequate for CAD use.

CAD users will need to scan in colour if they are scanning maps or coloured technical drawings. There are also drawings that are simply too poor quality to scan in black and white without losing a lot of information. These drawings are best scanned in greyscale or colour so that at least the information on them remains legible and usable, even if it will never be possible to (for example) use the scans for automatic raster to vector conversion.

Nextimage includes two colour options - Color (16.7 million colours) and Indexed Color (256 colours).

The Color option includes White Point and Black Point settings that you can use to ensure the paper background is pure white and the black parts of the document are pure black. There are brightness and contrast options that you can use to help enhance other colours.

256 colours are more than enough for any CAD or map application, so you may prefer to scan using the Indexed Color option. The advantage is that 256 colour files are much smaller than 24-bit colour files when opened up in applications.

When you scan a drawing using Nextimage's Indexed Color option, you have two options - Auto and Manual. If you choose the Auto option you can choose how many colors you want in the final scan, up to a maximum of 256. Nextimage then creates a scan containing the number of colours that you selected, these colours being the ones that Nextimage thinks best match the colours on the drawing. If you choose the Manual option, you can edit the colours chosen by the Auto option, or you can create your own entirely new set of colours (palette) by clicking on the colours within the drawing. You can also apply a previously saved palette.

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