identify dirts on screen using IMAQ

[trout00]

I have Vision and IMAQ software, I have a color screen with two dirty spots. How do I program the software to report the size and location of the spots?
Attached image is jpg size 736x554 pixels
I know how to convert the image to grayscale, I am not sure what to do next , histogram, userlookup.. before threshold because threshold require a value?? but the image color intensity may change from time to time.

[Kyle_V]

In this image, I extracted the red color plane first, and then performed an auto threshold in Vision Builder 6.1. The result was good. If the color intensity keeps changing, you may have to extract different color planes to see which one give you the best contrast.

Kyle V

[trout00]

Thanks for replying.
I would like to use Labview, and the user doesn't have to make a decision. The program should be able to report only two errors consistently. Right now I have errors at the edges. It is not reliable reporting only two errors.
You suggest extracting red color plane, is it because the screen is red? I also have a blue screen and a Green screen.
Every time the user installs the LCD screen, it's not perfectly align, one corner is higher or the screen shifted by 3-5 pixels.
Have you ever test an LCD b4? I need some help

[Kyle_V]

In the past, I've used NI's Display Test toolkit to test LCD displays. However, if you can send me some more example images, I should be able to create a LabVIEW VI for you that will detect only the two flaws.

Cheers.

Kyle V