Simple color detection by hue

Detect yellow regions in an image via thresholding in HSV color space.

Description

This script is a demo that shows you how to find objects of a certain color in an image. For this example I'm using the standard onion, peppers, or kids image that ships with the Image Processing Toolbox. You can also select one of your own color images instead if you wish. Then I separate the image into its component hue, saturation, and value color bands. I compute thresholds, and ultimately find a mask for the yellow objects. Prompts will guide you through the demo step by step. I multiply this mask by the original image to show the image with only the yellow objects showing and everything else blacked out. This script can be adapted to find other colors (white, green, blue, yellow, etc.)

If you want to do any measurements of the objects, I refer you to my blob measurement demo file at http://www.mathworks.com/matlabcentral/fileexchange/25157

Requires the Image Processing Toolbox. Tested with MATLAB release R2010a.

Acknowledgements

The author wishes to acknowledge the following in the creation of this submission:
Image Segmentation Tutorial ("BlobsDemo")

• MATLAB release: MATLAB 7.10 (2010a)

[Nasser]

a good work..

[Alain]

How can I change the color detection to red?

[Image Analyst]

Alain: You have to change the thresholds in the section that says "Assign the low and high thresholds for each color band." Red would have hue values less than about 0.1 and greater than about 0.9.

[neo]

thanx for this good works....but the others colors for exp the yelow and the magenta....how can i detect thissss...thanx againnnn..

[German Espinal]

Hi guys !!! I need to capture a primary color card with my webcam, then I need to determine what color is it ??? Can someone of you Help me please with the MatLab code ???? TKS A lot !!!

[neo]

hi guys i want to know...the diffrent steps of this program or the algorytm....thanx guysssss....n_n

[Image Analyst]

neo: You might want to look at my "Delta E" color detection submission. This lets you define (by outlining it) the color that you want to find.

[neo]

than you so much for answer me....i want to thank you very much for this good work....but i want to know the algorithgm that you use....thanx

[anju]

Would you be able to help on me on the matlab coding for the object tracking of the using Hue value ? As i am new to matlab i couldnt find much details on it .

My object is to perform color calibration in order to define the upper and lower limit of the HUE value for to detect the color at any light intensity .

[Bruno]

Thanks for your work. How you know what value to put in "Assign the low and high thresholds for each color band"? I want to detect Green. How can i know what values i have to use? Thanks

[neo]

hi....for bruno....the green hue thresholdlow=0.22..........
thresholdhigh=0.39.........
saturationthreshollow=0.15..
'''''''''''''''''hight=1
valuetresholdlow=0.15...
of course this values from my opinion...if you want to find yours:
1-go to paint.
2-select any color double clicks.
3-define customized colors.
you will find 2 systems-RGB-HSV...u will select your own threshold.......but i have always the same problem with the light intensity....good luck

[Jason]

 

[mishca nelson]

 I compute thresholds, and ultimately find a mask for the yellow objects.how do you do it?

[cesar pulgarin ortiz]

Hi, how can i compute the hi and low hsv thresholds for any color? i was trying with paint but i couldn't determine those numbers

[Image Analyst]

cesar: You could use my interactive thresholding application (also in my File Exchange)

[Image Analyst]

mischa: why the low rating? You can see how I do it simply by looking at my code. If you don't want fixed, hard coded values, then use my thresholding app to interactively select them.