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Troubleshooting Vector recognition

 

If you need to revectorize the image in the light of the points below, delete the existing vectors first by pressing Ctrl+F7 or selecting Run Menu > Undo Vectorization.

 

If no vectors have been recognized, or if the vectors that have been recognized are not what you were expecting, check the following.

 

Go through the Raster Quality Checklist

The most common reason for poor vectorization results is a poor quality raster image. Nowhere is the saying “Garbage In, Garbage Out” truer than in raster to vector conversion.

 

Make sure that the raster image is suitable for vectorization by going through the Raster Quality Checklist.

Do this even if you think the raster image is perfect. The image may look fine when viewed full screen but once you zoom into it and look properly you may find that it is not as good as you think.

 

If no vectors have been recognized or there is a single vector along the edge(s) of the image

You have probably converted a grayscale or color raster image without whitening the raster image background first.

Also check that no Pick Color is selected.

 

Does the vector image look like this?

If so, you have converted a grayscale or color raster image without whitening the raster image background first.

 

Vectorization settings

Check that the vectorization settings that are set are suitable for the raster image you are converting.

In the diagrams below the raster image is shown in gray and the vectors are superimposed in black.

 

Type Menu > Settings > General > Line Width

If thick lines contain double vectors, increase the Line Width.

 

Double vectors

Single vectors after increasing the Line Width

If you have to increase the Line Width it means that the lines on your raster image are thicker than would normally be expected on a scanned drawing. Thicker lines often have more unwanted protrusions and holes than thinner lines, so use Raster Effects Menu > Smooth () and Raster Effects Menu > Clean > Remove Holes() before vectorization.

You may want to try decreasing the resolution of your image to reduce the line thickness. To do this, use the DPI and Resample options in File Menu > Raster > Statistics.

 

Type Menu > Settings > General > Deviation Factor

If the vectors do not follow the lines on the raster image closely enough, decrease the Deviation Factor.

 

Loose vectors

Tight vectors after decreasing the Deviation Factor

If you have to decrease the Deviation Factor you may have scanned your drawing at too low a resolution. You may want to try rescanning it at a higher resolution.

 

Type Menu > Settings > General > Corner Snap

If corners are chamfered, increase the Corner Snap to sharpen them. You may also need to increase the Corner Snap angle tolerance in Type Menu > Settings > Advanced.

 

Chamfered corner

Sharp corner after increasing the Corner Snap

 

Type Menu > Settings > General > Pass-Thro Snap

If vectors do not cross neatly at untidy raster junctions, increase the Pass-Thro Snap.

 

Untidy junction

Neat junction after increasing the Pass-Thro Snap

 

Type Menu > Settings > General > Gap Jump Distance

If the vectors are broken at breaks in the raster image, increase the Gap Jump Distance.

 

Broken vectors

Continuous vectors after increasing the Gap Jump Distance

If there are a lot of breaks in your raster image you may be able to jump them more effectively if you use Raster Effects Menu > Thicken > Lines () and Raster Effects Menu > Thicken > Pixels () before vectorization.

 

Scan2CAD cannot jump gaps if the two sides of the gap are not on the same directional path – the vector on one side of the gap must point to the vector on the other side. This means that Scan2CAD cannot jump gaps on curves or circles.

 

Type Menu > Settings > General > Loose Ends Length

If you have a lot of loose end vectors, increase the Loose Ends Length.

 

Loose end vectors

No loose end vectors after increasing the Loose Ends Length

To avoid loose end vectors, use Raster Effects Menu > Smooth () before vectorization.

 

Type Menu > Settings > General > Connect Thro Nodes

If you want vector lines to pass at intersections rather than join, select Connect Thro Nodes.

In the diagrams below vector end points are enclosed in small squares.

 

Raster image

 

 

Vector image

 

Lines join at intersections

Lines pass at intersections

Connect Thro Nodes = off

Connect Thro Nodes = on

 

Arcs, Bezier curves and Circles always continue through intersections even if Connect Thro Nodes is off.

 

Type Menu > Settings > General > Align to Current Grid

If you want to snap vectors to a grid:

1. Select a grid spacing using Vector Edit Menu > Grid Snap Distance.

 To view the grid, press Shift+I or select View Menu > View Grid. Note that you will only be able to see the grid when you are zoomed in.

 

In the diagrams below the raster image and grid lines are shown in gray and the vectors are superimposed in black.

 

Vectors not snapped to a grid

Vectors snapped to a grid

Align to Current Grid = off

Align to Current Grid = on

 

Type Menu > Settings > Angle Optimization

If the vectors deviate slightly from their correct angles due to variations in the raster image beneath, set Angle Optimization. For example:

 

Angle Optimization 90/180 = off

Angle Optimization 90/180 = on

When Angle Optimization 90/180 is on, lines within a user-specified tolerance of 90 or 180 degrees are snapped to 90 or 180 degrees.

 

Angle Optimization 45 = off

Angle Optimization 45 = on

When Angle Optimization 45 is on, lines within a user-specified tolerance of 45 degrees are snapped to 45 degrees.

 

If Angle Optimization does not appear to be working, this is because Scan2CAD has chosen not to optimize a line or lines. It may do this if optimizing the line(s) would interfere with the logical position of a node.

 

If Angle Optimization is set on an image that does not have lines at the angles that have been selected for Angle Optimization, gross distortion of vectors can result:

In this case, turn Angle Optimization off.

 

Type Menu > Settings > Object Identification

Make sure that all the object types you want Scan2CAD to identify are selected.

 

To tell what type of objects have been identified, press the C key on your keyboard. This toggles between displaying vectors by color and displaying vectors by type.

When vectors are displayed by type, the different objects are colored as follows:

 

Continuous lines = red

If no objects are selected in the Object Identification tab the whole raster image will be converted to continuous lines.

If objects are selected in the Object Identification tab Scan2CAD will replace the continuous lines with the selected objects where possible.

 

Dash and dash dot lines = black

If no dash or dash dot lines are identified make sure that the Dash Line option is selected.

If dash and dash dot lines are still not identified try increasing the maximum dash and gap lengths in Type Menu > Settings > Advanced.

If too many dash and dash dot lines are identified try decreasing the maximum dash and gap lengths in Type Menu > Settings > Advanced.

 

Scan2CAD cannot recognize dashed lines where the dashes are very short (dots).

Scan2CAD cannot recognize dashed lines where they cross or join other entities.

Scan2CAD cannot recognize dashed curves or circles.

Scan2CAD cannot recognize dashed lines if the dashes don�t line up properly – the end of one dash must point to the next dash.

 

Arrow lines = gray

If no arrow lines are identified make sure that the Arrow Line option is selected.

If arrow lines are still not identified,  try increasing the max arrowhead length in Type Menu > Settings > Advanced.

If too many arrow lines are identified,  try decreasing the max arrowhead length in Type Menu > Settings > Advanced.

 Scan2CAD will also tend to recognize too many arrow lines if your raster image has thick, ragged raster lines. Try increasing Type Menu > Settings > Deviation Factor, which will reduce Scan2CAD’s sensitivity to the raggedness of the lines.

 

Hatch lines = brown

If no hatch lines are identified on your drawing, make sure that the Hatch option corresponding to the angle of the hatch lines you want to identify is selected.

If hatch lines are still not identified,  try increasing the Hatch Line angle tolerance in Type Menu > Settings > Advanced.

If too many hatch lines are identified,  try decreasing the Hatch Line angle tolerance in Type Menu > Settings > Advanced.

If hatch lines are identified but the lines are not parallel, select the angle in Type Menu > Settings > Angle Optimization that corresponds to the angle of the hatch lines you want to identify.

 

Polylines = green

If no polylines are identified on your drawing, make sure that the Polyline option is selected.

Alternatively, use Vector Edit Menu > Modify > Make Polylines to create polylines after vectorization.

 

If the polylines on your drawing stop at arcs instead of including them, ensure that Vector Edit Menu > Modify > Polyline Options > Include Arcs is checked.

 

Arcs = magenta, Bezier curves = pale blue

If no arcs are identified on your drawing, make sure that the Arc option is selected.

If small arcs are not identified,  try decreasing the Arc min radius in Type Menu > Settings > Advanced.

If too many small arcs are identified,  try increasing the Arc min radius in Type Menu > Settings > Advanced.

 

If no Bezier curves are identified on your drawing, make sure that the Bezier option is selected.

You can choose to identify arcs or Bezier curves but not both.

If the image is a typical architectural, mechanical or electrical drawing containing mainly straight lines, select arc.

If the image is mainly curvy, like a contour map, ship hull, aerofoil or freeform artwork you will get better results if you select Bezier. If you are vectorizing a curvy image with a view to cutting it on a CNC machine and the machine does not support splines you can still select Bezier. You can convert the Bezier curves to arcs or polylines on export.

 

Circles = dark blue

If no circles are identified on your drawing, make sure that the Circle option is selected.

If small circles are not identified,  try decreasing the Circle min radius in Type Menu > Settings > Advanced.

If too many small circles are identified,  try increasing the Circle min radius in Type Menu > Settings > Advanced.

 

Is a Pick Color selected?

If a Pick Color is selected, Scan2CAD only converts Pick Colored parts of the raster image.

Before converting an image with a Pick Color selected you must reduce the colors on the raster image or conversion will not work as you expect.

 

Are Layer Colors activated?

If Color Layers are activated, Scan2CAD only converts Layer Colored parts of the raster image.

Before converting an image with Layer Colors activated you must reduce the colors on the raster image or conversion will not work as you expect.

 

Does the image have white lines?

Scan2CAD does not recognize white lines because it assumes that the paper is white and that the drawing is non-white.

 

Has the image converted as a series of parallel vectors?

Scan2CAD assumes a black or colored drawing on a white paper background.

If the image is negative, i.e. what you want converted is displayed as white lines on a black background, the image will be converted as a series of parallel vectors:

 

Negative raster image

Parallel vectors

 

Click to convert a negative image to positive.

 

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