Prem's Knowledge Sharing

HSL vs RGB Aforge.NET Color Filter

2011-06-05T10:14:00.000-07:00

Yes, I am obsessed with color filters. And looks like that is what usually the hello world in image processing world to understand your image formats. Initially I have done color filters that are based on RGB. Last week in my lab we ran into an issue when we printed 6 blocks of color on white paper and kept it under a camera and used of filter to see how it works. Guess what? the filter showed red with magenta and other colors! That is not good. So why is it happening?
When we do a filter based on RGB, it looks for percentage of R, G and B in the a particular pixel. So it is a kind of relation. Let me give you a nice example
Assume I want to detect red color but I also have magenta color in the same image. My filter shows magenta as red! So I go to wikipedia (http://en.wikipedia.org/wiki/Magenta) and see why is it so and get something like this
RGB^B
(r, g, b)
(255, 0, 255)
HSV
(h, s, v)
(300°, 100%, 100^[1]%)

So when I used red filter in RGB space the magenta has 255 for R and 255 for B. So it will show up in both Red and Blue filter working in magenta.
But in HSV the value is 300. That is only one number. So when I filter my image in HSV and say 300 it will show only Magenta. For red it will be somewhere between 0 to 20. How I know the value, simple this image given below taken from Wikipedia (http://en.wikipedia.org/wiki/HSL_and_HSV) will help

I know we are all lazy, so here is the source code to grab image from webcam
Download (Source code to grab image from Web Cam using C# )(http://webpages.eng.wayne.edu/~dx8289/AforgeTutorial/Base/AforgeTutorial.zip)
After that we use AForge library by adding the Aforge.Imaging.dll to convert RGB to HSL. Added the following code for HSL filter and you’ll see the prefomance

void SelectedCam_NewFrame(object sender, NewFrameEventArgs eventArgs)
{
Bitmap image = (Bitmap)eventArgs.Frame.Clone();

//Reference : http://www.aforgenet.com/framework/docs/html/743311a9-6c27-972d-39d2-ddc383dd1dd4.htm

// set color ranges to keep red-orange
filter.Hue = new IntRange(0, 20);
filter.Saturation = new DoubleRange(0.5, 1);

// apply the filter
filter.ApplyInPlace(image);

// display in picture box
pictureBox1.Image = image;
}

Let me show how the image worked.
Given below is the image from my webcam that I am going to filter using HSL

I have added a magenta color printed in a paper and kept it at the background. Because you will see the real difference when you use a RGB to filter vs HSL for this image. I am not doing the RGB, but I will be giving the source code for this at the end of the post. So you are free to try based on the previous posts. After applying the HSL filter lets look how it looks

Tada!!!

There is no Magenta or any other color being showed. By tweaking the value you can get more better results.

You can download the source code by clicking down below

Click Here for Source Code for HSLFilter using Aforge

DLP RFID1 .NET DLL

2011-02-16T14:10:00.000-08:00

DLP RFID 1 API for IEEE15693 C# .NET

Download Here

RFIDCardDotNet.zip

I have been working on a project for the special education school. My project involves the use of RFID reader from DLP Design (http://www.dlpdesign.com/rf/rfid1.shtml). Being a typical .NET programmer, I wanted to develop my application in C# windows application using DLP RFID1 reader. I took the sample code from the DLP site (http://www.dlpdesign.com/rfrdr/) which was given in C++. I tried to write a wrapper around the existing library, but then came across a site/blog (http://www.electricrock.co.nz/tools/dlp-rfid1-library-for-linux/) who wrote about the details of the communication protocol. So I wrote according the to document and it worked!!! My system had a card already made and it runs on IEEE5693. So I wrote my DLP RFID1 .NET library only for this type of tag. I am attaching the download link for the library and also giving a screenshot tutorial of the library usage.

Add Reference as shown…

Add the files that you downloaded

And here is the code

..

using System;

using System.Text;

using RFIDCard;

..

if (!CardReader.DetectReader())

    Console.WriteLine(CardReader.ErrorMsg);

else

    Console.WriteLine(CardReader.ReadRFCard());

Sorry for poor documentation.

There are only 2 usable functions and 1 string variable.

Functions (static):

String Variable for error feedback (static):

Download Here

RFIDCardDotNet.zip

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Edge Detection using C# and Aforge.NET

2010-12-13T15:00:00.001-08:00

Edge Detection using C# and Aforge.NET

As I have told earlier, I am a newbie to image processing. I am posting things as I work on them. For the past few months I have been busy with my PhD qualifiers.

Our topic for today is Edge Detection.

Edge Detection:

First step in our segmentation is edge detection. I will take a simple example to do this. Here is the picture where I am going to do the processing. Actually it is not an image. It is a video stream.

Now I am going to do edge detection in it using Aforge. Before doing edge detection you should first convert into grayscale. There are mutliple ways to do edge detection [ Ref: http://www.aforgenet.com/framework/features/edge_detectors_filters.html]. Given below is the code snippet.

Bitmap image = (Bitmap)eventArgs.Frame.Clone();Bitmap gsImage = Grayscale.CommonAlgorithms.BT709.Apply(image);CannyEdgeDetector filter = new CannyEdgeDetector();Bitmap edge = filter.Apply(gsImage);pictureBox1.Image = (Bitmap)edge;

Actually I started this topic for image segmentation, but ended up as a Edge detection. I will come up with more topics. Also don’t forget to try other edge detection techniques given in Aforge.NET (link given below).

http://www.aforgenet.com/framework/features/edge_detectors_filters.html

AForge.NET color filter C#

2010-07-04T18:44:00.001-07:00

We are going to filter the colors of the video feed from a webcam. We will be using AForge.NET image processing framework for this and C#. You can check my previous posts for some basic video capture from webcam.

We have some steps as follows…

Acquire image from webcam (check previous posts - click here )
Create a color filter
Apply filter

Step 1: Check previous posts - click here

Step 2: Create a color filter

First a little modification to the UI

Then the code for the track bar.

Now as we move the slider, the variable for the RGB has to change accordingly. We have given the incremental/decremental value of 3. So when we move the slider, the value of RGB will change +3 or –3. You can change to required value by changing the TickFrequency value.

The main filter part. Please check this reference link/documentation ( http://www.aforgenet.com/framework/docs/html/35bd90e3-4e35-8f5f-e255-26c5d8d4b927.htm ). I have done the same with a little UI.

I am changing the value from 0 to the value in the track bar. You can add one more track bar for the lower value and can get a very good results.

Here is the reference and source for this step 2

Links : http://www.aforgenet.com/framework/docs/html/35bd90e3-4e35-8f5f-e255-26c5d8d4b927.htm

Step 3: Apply filter

Now run it !!!!!!!!!!!!!!!!!!!!!!!

It works !!!

Here are my results

The Original Screen (Before Processing)

Note the trackbar at full. Move your trackbar to maximum initially. Else you will not see anything. Because all the filter will be at 0. Which means block everything.

After applying value of red filter (look at the red trackbar)

Wow, the red is completely removed.

Now lets try Blue. (bring back red trackbar to maximum)

Light source is natural light (sun light) through window.

Same blue filter with indoor lightings. Yes. Lights do affect the result a lot.

Green filter test..

Ok, but not impressive. Because the lower limit of the filter is 0. If we move both upper and lower, we’ll get impressive results.

------------------------------------------- Using Lower Value for filter -----------------------------------------------------------------------

I just modified the UI so that I can change the lower value of the filter too. And I started playing to do some object isolation. Pretty nice. Here are some screen shots. Note the slide bar too.

Isolated the orange cup !!!!!!!!!!!!!!!1 success

Note :

Lightings play a major part in image processing. We need to add more things in the future to make it work under any lightings.
Camera also plays a major role. Due to some reasons, my camera shows green color in the background. Using good quality cameras, you can do miracles.

have a good day.
~Prem

Webcam using AForge.NET (Part II)

2010-07-04T18:39:00.001-07:00

Now to use webcam and I will go with the USB camera. I know the name of the camera (from the tutorial Part I, pop up box) as “USB2.0 Camera” and it is index as number 4 (from 0). You need to draw a picture box and a button to start the camera in the design view like this

Double click on the “Start Camera” button and we go to the code side. I am posting the code with comments. This will probably help you if you read the code.

And it works !!!!!!!!!!!!!!!!!!!!!!!!!

Ok, here is another video from a different site. I am not the author. But just a crash programming.

C# Tutorial - Getting Images from Webcam using Aforge from shivam on Vimeo.

Here is the link to the source of this video and author http://vimeo.com/7526663

Up coming tutorials will be on image processing. I will be posting as I am learning.

~Prem

Webcam using AForge.NET (Part I)

2010-07-04T18:36:00.001-07:00

Last tutorial we saw about setting up the environment to use AForge.NET. That was not a necessary tutorial, but it was my first post to see how to use windows live writer tool. And also that will give a sense satisfaction for people who have used OpenCV and trying AForge for the first time.

So now we have a window look like this. ( you can refer the previous tutorial to see how we set this environment).

Now the fun part. Programming !!!!!!!!!!!!!!!!!!!!!!!!!!

I am an Electrical guy, therefore according to records I am not a good programmer.

Press the “F7” function key to go the see the code of this form.

[or] right click on the form and select “View Code”

It is the same.

We will see a page like this

This is called the “code behind”. The previous one is called the “design view”. These are non standard terminologies used in programming environment. Just keep yourself updated because we’ll be using this in the upcoming tutorials.

Add these two namespaces

Before we use the webcam the code has to see the webcam (or ) the program has to know that there is a web cam attached to the computer. So here is our first aim

Aim : To list the USB camera attached to my computer

Put a button in the form. So when we click on the button, it is going to popup box for each camera.

Double click on the button and it will create a function. They call it the event handler. So when the applications is running and we click on the button, it will go to this function.

Now we are going to add code into this function so when we click the button it should list the USB camera attached to this computer (or laptop in my case). I will add the code and then explain the code with inline comments. I don’t want to add more screenshots and make this boring. So look at the following screenshot and try to read and understand the inline comments which will explain what is what.

Now lets compile the code using the shortcut key (im sorry, im used to it. Sort of fun) [ Ctrl + Shift + b ] or you can directly run it by pressing the function key “F5”. But “F5” will properly execute only if the code has no errors.

Lets see what result I got when I ran this program. I got 2 Camera’s in my laptop. So lets see if it lists them all. The following screenshots are my outputs.

I got 2 outputs !!!

1^st Camera - HP Webcam

2^nd Camera – USB camera

Awesome!!!!!!!!!!!!!!!!!!! AForge.NET got the list of camera’s connected to my computer.

Next tutorial is how to read video from a USB camera (a webcam in my case).

~Prem

AForge.NET <> Visual Studio 2010 Setup (Tutorial)

2010-07-04T18:13:00.001-07:00

First we have to download AForge.NET from here ---> AForge.NET library Download. Assuming we are using a Windows OS, download the latest .exe. After downloading install it.

Once installed we will be able to see the binaries in here

C:\Program Files (x86)\AForge.NET\Framework\Release - For 64 bit OS

C:\Program Files\AForge.NET\Framework\Release - For 32 bit OS

Now I assume we already have Visual studio installed in you computer. I will be demoing with VS2010 (even 2008 is compatible).

File –> New –> Project

Select “Windows Forms Application”

Then we get a window like this

Add AForge.NET libraries as reference. To do this right click on Reference (in Solution explorer).

The browse to the folder where we installed the AForge.NET libraries

C:\Program Files (x86)\AForge.NET\Framework\Release - For 64 bit OS

C:\Program Files\AForge.NET\Framework\Release - For 32 bit OS

Since our next tutorial is going to be on using AForge.NET with Webcam, we are going to add only the required binaries (.dll) namely Aforge.Video.dll and Aforge.DirectShow.dll.

On click “OK” we should be able to see the binaries (.dll) listed in the solution explorer under the reference folder like this

Done !!!! Now we have our environment ready to do some basic webcam stuff.

See you in next tutorial.

~Prem

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