Photo Silhoutte (Profile) in VB

[IMSlo]

I would like to write a VB program that would write GCode to cut a Silhoutte ( I don't know how to spell Silhoutte) from a digital photo. Please don't suggest buying software to do this. I built JGRO's router. SWMBO (for yall who still don't know what that is She Who Must Be Obeyed) does not share nor appreciate my enthusiasm for the CNC router. She says we need new carpet, the bathroom remodeled, and our 30 year old oven replaced. And in fairness to her the router has not done much more than take up space in my already cluttered wood working shop.

I have some expericnce in VB. I have written extensive applications in MSAccess which uses VBA. I have a program that was free on the internet that does a good job of edge detection and the person who wrote it was good enough to allow public access to the source code. The way the program works is after determining the width in x pixels and the height in y pixel it starts at X1 and moves across the entire photo one x pixel at a time. At each x pixel it moves up the y pixels for the entire height of the photo. If a pixel need to be turned on it does it. I can capture the xy position of those turned on pixels. The big problem is that they are far from cnc order. I have begun to try to figure out an algorythm to compute the logical order for cutting and write the Gcode. I would assume that each pixel is a unit. Of course it would have to be scaled down drastically. It seems that there are seven possible positions (9 minus present and last positions) for the next point. This seems relatively simple but there are times when I have seen gaps when zooming in on the edge detection and I have have seen multiple lines. I can imagine the program hanging up looking for a nonexistant point or going back and forth between multiple lines. I have not really started on this project and very possibly might never. I would just like to hear some ideas from others if you would be willing to share.

[nikolatesla20]

Hi, this is possible to do by writing a "following" algorithm which walks the edge of the image. Firstly,however, for a digital photo image you need to do image enhancement using and edge detector called a canny edge detector. The canny detector usually gives you a nice 1 pixel edge. After that you can use an algorithm which will simply follow the edge - basically tracing along it. This will put the pixels in the right order automatically. After that you can then also walk thru the points and calculate the angles between each pixel - if the pixel is straight, for example, like the pixel above the current one is straight above, you could optimize the line by just jumping to that location until a pixel "shift" occurs which would indicate the line is changing direction.

Really you only need basic math to do the more complex stuff, the canny edge detector is the most difficult part to implement, but it is certianly doable even in VB (although it may be a bit slower)

-niko

[rippersoft]

Here is some research material:
http://www.greyc.ensicaen.fr/~dtschump/greycstoration/
http://potrace.sourceforge.net/
http://www.inkscape.org/
http://www.roitsystems.com/cgi-bin/autotrace/tracer.pl
http://sourceforge.net/projects/autotrace
http://autotrace.sourceforge.net/frontline/

Good Luck,
RipperSoftware

[IMSlo]

Thanks for the replys fellows. It looked as if there would be no replys.
Progress:
I am working with VB Net 2005.
I have the form built.
I can load, crop, and flip/rotate the image.
I am converting the working image to 8bbpindexed monochrome. (Thanks to Bob Powell's tutorials.)
Problems:
I made the image 8 bits per pixel instead of 1 bit per pixel to avoid bit shifting etc. in isolating a pixel.
I made the image only two colors because I thought this would make edge detection easier. I have not been able to accomplish edge detection. The method I have been trying to use compares the current pixel to the left, right, above and below pixels. If it is different from any of these I set the color black. If all are the same I set the pixel white. This should result in a black outline on a white image. I am using Marshal.ReadByte and Marshal.WriteByte to accomplish this. I always end up with a completly white or a completely black image depending on the I set the conditions. I am stumped at present. I must be making some wrong intrepretations. Maybe I will get a revelation during aone of my daily walks.

[IMSlo]

Just got my outline working. The procedure I was using was right. I was trying to do too much in one step. The photos I am using are already almost silhouttes. They are profiles of my grandaughter taken in front of an outside window. They are backlighted.
During this fiasco I have learned quite a bit about image manipulation in VB Net. Now I am about to get whipped by databases.
I think I will take a walk and then jump into coordinate saving, scaling, sorting,etc etc.

[vacpress]

imslo - cool...

i would be interested in seeing your code, just out of curiosity. i am trying to increase my vb-based killing power... havent moved to .net yet tho... i am afraid of loosing my beloved object arrays!

[Switcher]

Check out, "Paint .NET" Open source, written in C# (105,000 lines of code). I know you said VB .NET, maybe you can convert what you need with the last link.

http://www.eecs.wsu.edu/paint.net/download.html#src (Download Source)

http://www.eecs.wsu.edu/paint.net/index.html

http://www.developerfusion.co.uk/uti...sharptovb.aspx (Convert C# to VB.NET)

.

[IMSlo]

vacpress it's just too primative for anyone to run except me right now. There is a certain operating sequence that must be followed, if the image has too much detail the outline results in garble etc, etc. etc.

Switcher, thanks for the links but I think I am done with graphics on this project. I can't even think about getting into C# now.

I have just started looking at SQL at first glance it seems to be a booger. I am very familiar with MSAccess and I thought that might help me with SQL. The only thing that Access is helping with is the understanding of tables, queries and relationships.

It appears that the difference between Access and SQL is like the difference Windows and DOS.

My goal is to save the xy coordinates of the pixels in the outline, scale them down to a useable size, sort them in a logical cutting order and write a GCode file.

I thought this would be easier than the graphic manipulation but right now it seems insurmountable. Maybe it will come around.

[Switcher]

Since you have the outline working, why not just write the X & Y Pixel location to a textbox, send that info to a simple text file, name the files in the order you want them to be cut (file1.txt , file2.txt , file3.txt ...) then call all the sub files to create a complete file.

[IMSlo]

Switcher, I'm afraid it's going to be too complicated to do what you suggest. There are a couple of big problems. The first is size (height and width). I will treat these pixel coordinates as units (inches). These could be hundreds high and wide. The way I would handle this is decide how high or wide I wanted the finished product, probably an options on a form, then divide this number by the max x or y. I then would have to multiply all x and y's by the result of this division.

The next is order of the coordinates. The coordinates are generated by starting at y0 x0 scanning in the x direction until max x is reached. When a black pixel is found its location is recorded. The scanning would go to y1 x0 etc until the whole image is scanned. I don't believe the order that comes from scanning will be anywhere close to logical cutting order. I think I must store the coordinates in a place where they can be manipulated before they are exported into a G Code file. Database files are ideal for this type stuff. My problem is that I know nothing about Microsoft SQL database operations and must start at the bottom again. (I had to start at the bottom with VB Net Graphics also to get the outline.) Maybe if I keep digging I will get it. Thanks for the suggestion and interest.

[Switcher]

Yeah, I know what your talking about ,as far as the graphics. I just started a program with GDI+ (VB .NET 2003). It's not bad though, once you figure out the basics.

[IMSlo]

Switcher, I couldn't help but notice that you say you are using VB.NET 2003. You probably know that Microsoft is giving away VB.NET 2005 Express, or at least were a few months ago. I don't know if there's much difference in the 2 but I always like to have the latest version of any free software.