Comments on: Object recognition: current process

By: blog.je2050.de - blog and database of joa ebert » Imageprocessing results

blog.je2050.de - blog and database of joa ebert » Imageprocessing results — Sun, 18 Jun 2006 09:32:50 +0000

[...] joa @ June 18, 2006

Maybe you remember me some days ago talking about research and object recognition. I finished it and had to present the theoretical background and practical working example. What c [...]

By: Michaud

Michaud — Fri, 03 Feb 2006 13:08:22 +0000

A post is always good cause its also interresting for other people. My address is m-i-c-h_a_ u-d=At=v_e-n ~a *n^. nl (remove all the none alphabetic chars an change the At into @).

By: joa

joa — Thu, 02 Feb 2006 13:43:45 +0000

No, but it might be the webstats counter. Thanks for the information I’ll remove that thing.

About the background/foreground: Leave me your eMail or maybe I will create a post here about how to check between back and foreground easily in AS3. It is not that hard even using a webcam. There are simple approaches.

By: Michaud

Michaud — Thu, 02 Feb 2006 10:42:39 +0000

Do you know you have a popup advertisment running on your page?

By: Michaud

Michaud — Thu, 02 Feb 2006 10:40:33 +0000

In principal the background is mostly static because i use a webcam feed and because its a live feed determining the background by clicking is not realy an option. But combining the idea of having a static background and measuring the changes in the bitmapdata could make localizing motion detection quite cool!!
Foreground and background detection would be even cooler!! :)

By: joa

joa — Thu, 02 Feb 2006 06:59:15 +0000

Do you have a static background or is the background changing? There are some (complex) algorithms to determine what is in the background and what is in the foreground.

There are also simple solutions. You could set the background by pressing a button and you would know what other objects are in front of the camera. Using scanlines to determine the outline would become much more easier.

By: Michaud

Michaud — Wed, 01 Feb 2006 23:04:32 +0000

Thats right, that was one of the tactics i concidered but then the center could be a hole… :) And i have no way of deciding either way
i’ve got another solution working now. I use scanlines to run through the pixels and look for outlines. I run along the points of the outline and save the boundry points on a scanline for that outline. When i’ve got an outline, using the boundry points, i scanline the inner space of the outline for holes. I also mark the inner points as points of the outline. When i do that i can ignore the inner space of the outline and still scan the inside of the holes for other outlines.

Its all pretty rough and none scientific but it seems to work. There are some problems because scanning for holes with the boudries of an outline on a scanline i could still hit an outline outside of the current outline.
But i think there’s no way of determining, within the context of an scanline if i find a hole or an outline.

By: joa

joa — Wed, 01 Feb 2006 12:56:28 +0000

If you know the outline and got some connective points of that polygon you could calculate the center. Then you could walk from the center in a circular directions to the outlines and everything you cross there will be a hole.

By: Michaud

Michaud — Tue, 31 Jan 2006 23:10:53 +0000

iv’e checked the topics you named but you’re thinking in a far too complicated direction. Its like a two dimensional doughnut. it has a hole. i’m trying to find the hole but then with an irregular polygon with a irregular polygon hole.

By: joa

joa — Tue, 31 Jan 2006 21:22:46 +0000

I don’t know waht you want to achieve. But maybe you need the medial axis of an object.
This is only the “inline” of an object. It could also be usefull for you.

It is a shame that I can’t find any good link for that topic. It belongs to terms of Voronoi Diagrams and Skeletonization.

By: Michaud

Michaud — Tue, 31 Jan 2006 20:48:14 +0000

I see: Shape space estimation is far to mathematical for me. Im a designer trying to make things i imagine…

By: Michaud

Michaud — Tue, 31 Jan 2006 20:36:21 +0000

Probably not, cause i don’t know what that is ;). No, I blur the image, make the contrast so high that the image turns black and white. then, scanlining through the image i find a black pixel above and a white pixel below. When i find this combination, i follow the edge round till i’m back at the start. Ofcource i register the information in a 2 dim Array. It works quite good. At this moment i rely on the scanline also to continue checking for holes but that makes it dificult to find out if there is a hole.

By: joa

joa — Tue, 31 Jan 2006 17:22:35 +0000

You are using shape-space estimation?

By: Michaud

Michaud — Tue, 31 Jan 2006 13:30:13 +0000

I’ve been working on a vector trace class in the Flex 2.0 IDE. (AS 3.0). I’ve got the contours of the objects working but the holes in the objects are a pain. The contours are realized by making the image black and white. But deciding if a boundry is a hole or just a boundry is still quite difficult…
The trace of a 160×120 webcam feed takes about 0.5 sec but that’s before i have optimized the tracing code
Ofcourse, working with C++ gives you more tools