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ranger.sean81 post(s)
#05-Apr-19 00:05

Hi folks

I need to trace part of an image in M8.0.30, but all tracing tools expect the colour selection button are greyed out. Likewise the colour selection tool when I make the image the active layer. Also, opening the image directly (as in, not in a map) in Manifold doesn't provide any tools either.

The image is stored locally within the project, and together with a drawing is the only layer in the map.

I *think* I'm doing everything as per the help doc - can anyone offer any guidance?

Thanks, Sean


5,359 post(s)
#05-Apr-19 08:42

Also, opening the image directly (as in, not in a map) in Manifold doesn't provide any tools either.

Correct. Tracing tools work with maps. From the Tracing Tools topic :

The Tracingtoolbar works within maps to create objects in drawings by using pixels in an image layer to guide the creation of objects in a drawing layer.

Put your image in a map together with a (usually blank) drawing. See the last example in the topic above, that uses the Montara Mountain surface, for a step by step example. That example starts with some preparatory steps manipulating the image to get it into better shape for more effective vectorization ("tracing").

drtees57 post(s)
#05-Apr-19 20:04

It is also very helpful to have the Tool Properties Pane open as well. The default value tolerance is set to 5. I find that this value should be set higher to take into account subtle changes in color values in an image. I usually accomplish my goal through trial-and-error until I find a tolerance value that allows me to trace the thing I want. Most recently, I needed a drawing layer of a very large stormwater pond. This pond is not included on any of the government GIS sites where I usually get my data. I georeferenced an image saved from Google Earth Pro and use that image to trace the area of the stormwater pond. On screen, the pond appears to be a dark brownish-green color surrounded by tan-colored vegetation. However, the pond's color at the pixel level includes many different values and chroma of dark green. I believe I set the Tolerance Value to 30 in order to capture all of the stormwater pond. I then simplified the resultant area to get rid of the edge noise.

The downside of this process is that it can take M8 quite a while to trace a large image.


1,916 post(s)
#05-Apr-19 20:42

Converting the image into a Palette with a reduced color range also helps.

Aussie Nature Shots

ranger.sean81 post(s)
#06-Apr-19 22:12

Thanks for the responses - turns out I missed the help topic statement that tracing tools don't work with compressed images.

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