Trying to count pixels in a mask

I have a variable called MASK2 and want to count the pixels in it using the following layout that has been given to me

function number=pixcount(BLANK)

number=0; 
for n=BLANK:BLANK

    for m=BLANK:BLANK

        if BLANK(n,m)==1

            number=number+1;

        BLANK
    BLANK
BLANK

So I have written the following

function number=pixcount(MASK2)

number=0;
for n=1:1500

    for m=1:977
        if MASK2(n,m)==1
            number=number+1;
        end
    end
end

but get an error message on line 5 saying Input argument "MASK2" is undefined.

Error in ==> maskloop at 5 if MASK2(n,m)==1

What am I doing wrong? Thanks.

Answer 1

[Friedrich]

Hi,

sounds like you are calling your function without an input like pixcount(). Try to pass something, like pixcount(rand(1500,997)).

But in general you can count 1 a bit faster, e.g.

number = sum(sum(Mask2==1))

If Mask2 is a logical matrix than you can do

number = sum(sum(Mask2))

[Image Analyst]

rand(1500,997) will never = 1 so the number will always = 0.

Answer 2

[Image Analyst]

You can't just run that function without calling it with a defined matrix. You need to call it from another function (if it's in the same file) or from a separate script. For example in script1.m:

m = rand(100);
mask2 = m > 0.7;
% Now call the function:
pixelCount = pixcount(mask2);

Then in pixcount.m:

function number=pixcount(MASK2)

number=0;
[rows columns numberOfColorChannels] = size(MASK2)
for n=1:rows
    for m=1:columns
        if MASK2(n,m)==1
            number=number+1;
        end
    end
end

And, like Frederich said, that's not an efficient way to do what it ends up doing.