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From: JordanPainter Painter on 13 Apr 2010 09:18
Hiya, I'm trying to set a threshold to reduce my values to 1's and 0's then get a total of these 0's and 1's so i can work out a ratio of black to white? My image is a a large jpeg file.

I've tried this so far:

im = 'image.jpg';
im = uint8(im);

level = graythresh(im);
BW = im2bw(im,level);

x = imread(BW);

blackcount = sum(BW(1,:))
whitecount = sum(BW(:,1))

I used the sum code at the bottom for just the standard image but it only pulled up the completely white and completely black pixels i think. So i added the threshold but i can't get it to work. Any help is welcome, thanks a lot!
From: ImageAnalyst on 13 Apr 2010 12:14
blackCount = sum(sum(BW == 0));
whiteCount = sum(sum(BW));

That x=imread(BW) line is unneeded and wrong, as well as your indices
in your count lines. Also, make sure im is 2D monochrome, not 3D RGB
image.
From: JordanPainter Painter on 13 Apr 2010 12:44
ImageAnalyst <imageanalyst(a)mailinator.com> wrote in message <db7d7856-358d-4d47-aaf1-500e413542dc(a)u22g2000yqf.googlegroups.com>...
> blackCount = sum(sum(BW == 0));
> whiteCount = sum(sum(BW));
>
> That x=imread(BW) line is unneeded and wrong, as well as your indices
> in your count lines. Also, make sure im is 2D monochrome, not 3D RGB
> image.

Ah right, i tried your values instead. It seems to only view one line of 9 pixels instead of the entire matrix. Other than that i think this works. Any ideas on how to get it analyse the entire image. Thanks :)
From: JordanPainter Painter on 13 Apr 2010 13:15
This is my latest code:

im = 'crack.jpg';
im = uint8(im);
% imshow(im);
level = graythresh(im);
BW = im2bw(im,level);
imwrite(BW,'black.jpg');
img = 'black.jpg';
imread(img);

blackcount = sum(sum(img == 0))
whitecount = sum(sum(img))

It gives me the answer:

blackcount = 0
whitecount = 876

I'm not sure if saving the output black and white file and then using imread on that is the right idea?
From: Steven Lord on 13 Apr 2010 13:33

"JordanPainter Painter" <jordanpainter(a)hotmail.co.uk> wrote in message
news:hq28rf$h9t$1(a)fred.mathworks.com...
> This is my latest code:
>
> im = 'crack.jpg';
> im = uint8(im);
> % imshow(im);
> level = graythresh(im);
> BW = im2bw(im,level);
> imwrite(BW,'black.jpg');
> img = 'black.jpg';
> imread(img);
>
> blackcount = sum(sum(img == 0))
> whitecount = sum(sum(img))
>
> It gives me the answer:
>
> blackcount = 0
> whitecount = 876
>
> I'm not sure if saving the output black and white file and then using
> imread on that is the right idea?

Those answers are correct for the code as written.

Hint 1: When you execute the lines when you compute blackcount and
whitecount, what does the variable img contain?

Hint 2: Call IMREAD with an output argument.

--
Steve Lord
slord(a)mathworks.com
comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ


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