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AutoTrace - Step 2: Tracing elements

AutoTrace a Background image - Step 2: Tracing elements      Pro  version only  

After finishing the first step ( Step 1 - Raster preprocessing), you can start the Tracing Step.

A note: we define here as Tracing the conversion of a line/curve of black pixels in a Cad element, like a Polyline, closed Polyline, Circle, Arc, Ellipse, Spline, Closed Spline

All the Tracing functions are included in the second Frame of the dialog:

Lets begin with the list of the parameters and functions included there:

• Traced elements list: here you can see the list of the Traced elements, including the type of element (Polyline, closed Polyline, Circle, Arc, Ellipse, Spline, Closed Spline). Of course the list is empty when you start the dialog. When you select an element it will be rendered thicker in the graphic window.
• Tracing tolerance: this is the basic tolerance value used during the Tracing operation. The value is in pixels, and you can also read the size of a single pixel. In the Tracing settings  dialog you can then set some tolerance factor for some special cases.
• Follow intersecating elements as well. If this option is enabled, when you click an element in the raster image will be traced not only it, but also all the intersecating elements. In this way you can Trace a group of connected elements (lines, curves) in a faster way.
• Show Vertices. If this option is enabled you can see also the vertices of the Traced elements, rendered with a little Green square.
• Trace all elements! Pressing this button ALL the elements included in the raster (or in the selected zone) will be traced. This is the fastest way to go if you want to trace all what you can see
• Delete selected element. Pressing this button the element selected in the Traced element list will be deleted
• Delete ALL elements. Pressing this button ALL the elements included in the Traced element list will be deleted. If you want Trace again elements rememeber to click the 'Reset deleted Pixels' button before!
• Reset deleted Pixels. A brief introduction: when you trace an element all the pixels crossed by that element are marked as deleted. This is to avoid to trace more times the same elements. In the combo box included in the Raster preprocessing frame you can select if you want to see on the screen also the marked as deleted pixels or not. If you need to trace again some elements, you need to unmark the pixels: this is what this button does.
• Tracing settings: goes to the Tracing settings dialog, where you can fine tune the way the elements are traced.
• When you click the graphic windows try to :
  • Trace a new element - clicking a black line/curve in the graphic window it will be traced (manual Tracing)
  • Select a traced element - clicking a red traced element it will be selected in the Traced elements list.

You can adjust the transparency of the raster image scrolling the included cursor.

Now the content of the frame is explained, but lets add some more information.

You can Trace elements in two ways:

• Automatic tracing: simply press the Trace all elements! button and ALL the elements included in the raster (or in the selected zone) will be traced. You can then delete some unwanted elements here or after in the Cad Drawing window. You can also setup a minimal length for the elements to trace, see Tracing settings  dialog.
• Manual tracing: click some black line/curve in the graphic window (with Trace a new element mode enabled!) and it will be traced. If the Follow intersecating elements as well option is enabled, also the intersected line/curves will be recursively traced. This can speed up a lot the Tracing of a group of connected elements.

I repeat here an important concept: when you trace an element all the pixel crossed by that element are marked as deleted. This is to avoid to trace more times the same elements. In the combo box included in the Raster preprocessing frame you can select if you want see on the screen also the marked as deleted pixels or not. If you need to trace again some elements, you need to unmark the pixels, using the Reset deleted Pixels. button.

The traced elements are rendered in Red in the graphic window. The selected one is thicker. You can see the vertices of the Traced elements enabling the Show Vertices option.

When the Tracing job is finished press the OK button, and all of them will be added to the Cad Drawing

See also Autotracing for a step by step example

 Pro  version only