Tracing bitmap image contours

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Dennis9412
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Tracing bitmap image contours

Post by Dennis9412 » Thu Nov 19, 2015 7:41 pm

Hi there,

I'm very new to QCad and have absolutely no CAD experience at all. I am planning on using QCAD to assist me in making DXF files that can be converted into .DAT files to be used in a CNC foamcutter. I need to be able to load a .BMP file into QCAD, trace the image outline with a polyline and save it as a dxf file. I can then convert the dxf file into a dat file which will allow me to cut that shape in a block of foam.

Can this be done? And if so, how is it done?

I am running Windows 7 with the free QCAD version 3.11.3

Thank you for any assistance you can provide.

Regards,

Dennis

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Husky
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Re: Tracing bitmap image contours

Post by Husky » Thu Nov 19, 2015 9:46 pm

Hi Dennis - welcome to the forum!
Dennis9412 wrote:Can this be done? And if so, how is it done?

I am running Windows 7 with the free QCAD version 3.11.3
Yes! You can insert a bitmap in your drawing area and trace it manually with all available tools in QCAD. :wink:
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Dennis9412
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Re: Tracing bitmap image contours

Post by Dennis9412 » Sat Nov 21, 2015 5:14 pm

Well thank you for the reply, Mr. Husky.

As I mentioned in the opening post, "I have absolutely no CAD experience at all", so I would require step by step instructions to, as you say, "insert a bitmap in your drawing area and trace it manually with all available tools in QCAD"

I'm not trying to be a smart ass Husky, but your above statement does not give me any idea how to do accomplish this task, as I know nothing about CAD, but I am trying to learn. If possible, could you steer me to a post or a video which explains the procedure?

Thanks in advance for your assistance.

Regards,

Dennis

Panchdara
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Re: Tracing bitmap image contours

Post by Panchdara » Wed Nov 25, 2015 4:19 pm

Hi Dennis. My first post here too. And, I like you, am a total novice. Anyway, reading other bitz and bitz, I see you can convert images to dxf from InkScape. Maybe that's a start?

Best
Win 10, QCAD 3.23

Dennis9412
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Re: Tracing bitmap image contours

Post by Dennis9412 » Sat Nov 28, 2015 2:14 am

Well thank you Panchdara. That's the first helpful response I got since I asked the question. I'll give that a try.

I guess the rest of these guys aren't interested in helping out a new CAD user.

We're obviously not on their level. I guess this is an old boys club here.

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andrew
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Re: Tracing bitmap image contours

Post by andrew » Sat Nov 28, 2015 12:32 pm

Dennis9412 wrote:I guess the rest of these guys aren't interested in helping out a new CAD user.
We're obviously not on their level. I guess this is an old boys club here.
A tip that might help to get better replies:

Ask clear questions! Or even better: attach your drawing or at least a screenshot.

We other guys have not seen the drawing or files you are working with. Is it a simple rectangle, an art work or a precise drawing of a mechanical piece? This all makes a big difference:
- If you are intending to create a precise drawing of a mechanical piece from a bitmap, you are looking at manually tracing it or redrawing it using all the various CAD tools QCAD has to offer. In this case, there is no easy answer to your question.
- If you are talking about a piece of art, it's an entirely different story: precision is irrelevant and you are likely looking at an automatic conversion process, for example using Inkscape.

Anyway: please be as specific as possible when asking questions. Be not surprised if a vague question will get a vague response :wink:

Dennis9412
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Re: Tracing bitmap image contours

Post by Dennis9412 » Sat Nov 28, 2015 1:27 pm

Thank yoyuAndrew, now we are getting somewhere. As I mentioned in my first post, I am trying to cut some foam pieces with my CNC cutter. Attached is a bitmap of a turtledeck that I am trying to cut. This is the front piece, and it will be mated to a second piece. In order for the CNC cutter to work, the drawing should be one continuous line or polyline I guess you'd call it.

Can you tell me how I go about converting this BMP file to a dxf file using QCAD?
Attachments
Turtledeck front.bmp
Turtledeck front.bmp (123.35 KiB) Viewed 6098 times

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Clive
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Re: Tracing bitmap image contours

Post by Clive » Mon Nov 30, 2015 1:31 pm

Dennis9412 wrote:Well thank you Panchdara. That's the first helpful response I got since I asked the question. I'll give that a try.

I guess the rest of these guys aren't interested in helping out a new CAD user.

We're obviously not on their level. I guess this is an old boys club here.
Hello Dennis

An 'Old Boy' here.

I find you're approach quite abrupt and rude if I'm being completely honest Dennis, You ask questions without using the word please and then you get grumpy because no one has any answers for you. Well if you're still reading at this stage let me tell you that questions are very kindly answered by people who are busy and not paid in anyway at all!

The kind of result you are trying to achieve would need to be done by using probably a mix of programs, QCAD specifically is a CAD only program and does not have any options to work with sketches,illustrations of the like. To my knowledge even the bigger CAD programs like AutoCAD and Microstation do not have the features to accurately do what you want.

You could scan your image by using a scanner of course, some scanners have the function to save to different formats - but my knowledge is limited with this.

As mentioned earlier Inkscape would be the way to go or by using a 'paid for' program like Adobe illustrator or Coreldraw.

Regards

Clive

Dennis9412
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Re: Tracing bitmap image contours

Post by Dennis9412 » Tue Dec 01, 2015 6:05 pm

Hello Clive,

First of all, my apologies to all the regulars here who give freely of their time trying to help us raw CAD beginners.

Your input here makes life for the "newbies" much easier, and we thank you for that.

I can assure you that it was not my intention to be rude and abrupt, and I am truly sorry that it was perceived that way.

It was my understanding that it was a simple process to "trace" a bmp file with a cad program and turn the outline into a polyline.

Obviously that is not the case, and my "simple fix" to my problem is going to be more involved than I thought it was.

Once again, I am truly sorry for offending anyone here.

Thank you for your understanding.

Regards,

Dennis

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Clive
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Re: Tracing bitmap image contours

Post by Clive » Tue Dec 01, 2015 10:03 pm

Dennis

Thanks, much appreciated.

Right, moving forward. If you have geometric information like arc radius’s and lengths at hand it would be easier to just draw this thing right out directly with QCAD, if not I think what I would do is place points (use a different layer) accurately at specific coordinates and draw arcs then clean up and convert to a continuous polyline - all this I would do just for one half only, then I would mirror this half to form the whole.

If all this sounds too much to begin with, send me the file you have with as much info as possible and I'll work it and send it back to you, then if you like I'll walk you through the steps to achieve something like this! I'm not too busy at the moment, all my students are finishing off for the Christmas break/half term :wink:

Regards

Clive

Dennis9412
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Re: Tracing bitmap image contours

Post by Dennis9412 » Wed Dec 02, 2015 4:17 pm

Thanks for the quick reply Clive, much appreciated.

I think I'm beginning to get an idea. Please correct me if I'm wrong.

If I import my bmp file in the first layer, then place dots over the bmp in the second layer, then join the dots with arcs I could get my copy.

Again, being new to CAD, the layer thing is something I would not have thought of.

Am I heading in the right direction here?

Thanks,

Regards,

Dennis

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Clive
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Re: Tracing bitmap image contours

Post by Clive » Wed Dec 02, 2015 4:27 pm

Hi dennis

Yes you're on the right track there, set up layers for things like - Outline, Construction, Hidden lines, center lines, Text, construction points etc...etc..

The beauty and good practice of using layers is that you can manage them, turn on or off, change colour, line weight and stroke if needed.

When you've created arcs you can trim any overlapping parts.

Clive

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