Whiten the raster image background


Look at the Title Bar at the top of the Scan2CAD screen. There is a number after the name of the raster image.


If this number is 16, 256 or 16.7M it means that the image has a color depth of 16, 256 or 16.7 million. This means that although the image background may look white it is almost certainly off white.

Off white background White background

By default Scan2CAD processes all the non-white parts of an image it sees on a white background. This means that you need to whiten the background before processing the image. If you do not do this, some Scan2CAD functions will appear not to work at all or will produce unexpected results as apparently white areas of the image are processed.

We recommend that you use one of the following methods to whiten the background:


Simple or adaptive threshold

Using a simple or adaptive threshold will make the background white and the rest of the image black.

Before After

Select Raster Effects Menu > Threshold > Simple () or Raster Effects Menu > Threshold > Adaptive ().


Once you have thresholded the image we suggest you:

Use Palette Menu > Reduce Color Depth > 1 Bit [Mono] to reduce the image’s color depth to two colors.
Use Raster Effects Menu > Smooth () to smooth the edges of the raster lines.
Use Raster Effects Menu > Clean > Remove Speckles () to remove any speckles.
Use Raster Effects Menu > Clean > Remove Holes () to remove any white holes in the black lines.


The Reduce Colors dialog

Using the Reduce Colors dialog will make the background white but leave the rest of the image in its existing color.

Before After
1. Select Palette Menu > View/Edit Palette.
2. Select the colors that are off white:

3. Select the Change To White option.

4. Click OK.


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