how to calculate the total white dots/ white region in this image

hi, i'm beginner of matlab. Please show me the ways to calculate the total white pixel/regions that appear on this image..thanks http://imageshack.us/photo/my-images/841/result2cars.jpg/ http://img841.imageshack.us/img841/810/result2cars.jpg

Answer 1

[Jeppe]

To read in the image, use

M = imread('result2cars.jpg');

Because your image is a grayscale image, M is just a matrix. Each entry corresponds to one pixel. The entries are integers from 0 (black) to 255 (white). To calculate the number of completely white pixels, use

sum(M(:) == 255)

If you accept very light gray as white as well, use

sum(M(:) > t)

where t sets the white tolerance. For example, using t = 128 would count all pixels who is brighter than 50% gray as being white.

Answer 2

[Image Analyst]

See my image segmentation tutorial "BlobsDemo": http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862 It will work for you.

Of course if you just want to count the white pixels, you can sum them like Jeppe said. But if you want measurements, like a count of the number of cars, their sizes, etc. then you'll have to use regionprops().