Create a binary image from a 2-dimensional binary [0 1] matrix

I've been trying for a while to draw shapes in the binary image function and it hasnt worked, I do not understand how to plot the coordinates of the shapes. Does anyone have any useful links or tips i can utilise?

[DGM]

Someone asked this recently. I'm assuming you also need to count the pixels as well?

[Nicholas]

Yes, I do need to count the pixels as well.

Answer 1

[Image Analyst]

Pretty trivial. First define the number of rows and columns in the image. Then define the x and y coordinates for one rectangle.

mask = false(rows, columns);

Then for one triangle, do

oneTriangle = mask & poly2mask(x, y, rows, columns);

Do that for all triangles. When done creating the mask, get the areas like this

props = regionprops(mask, 'Area');
allAreas = [props.Area]

I guess you haven't seen my tutorial yet. It's one of the most downloaded in the File Exchange and goes over basic stuff like this.

See my Image Processing Tutorial in my File Exchange:

Image Analyst's File Exchange

[Nicholas]

Thank you very much for the help

[Image Analyst]

OK, seems like you're having trouble. Here's another way to do it:

rows = 100;
columns = 100;
mask = false(rows, columns);
% Create a triangle in the upper left
for col = 1 : 50
    bottomRow = 50 - col + 1;
    mask(1 : bottomRow, col) = true;
end
% Create square at bottom middle
mask(76:100, 26:76) = 1;
imshow(~mask);

% Compute areas of all shapes.
props = regionprops(mask, 'Area');
allAreas = [props.Area]

allAreas = 1×2

1275 1275

Extend it for the other 3 shapes.

[Nicholas]

thank you for the help, I greatly appreciate it

Answer 2

[Jan]

What have you tried?

M = false(100, 100);
M(26:50, 76:100) = true;  % The black rectangle

Instead of setting all pixels to black by a single true on the righ side, you can insert a triangle shape:

M(1:5, 1:5) = tril(true(5));

See also: triu, rot90, transpose.

[DGM]

Bear in mind that the previous interpretation of the assignment stated that the blobs were black on white, so you'll have to complement M after assembling it.

% ... insert all the blobs

M = ~M; % then invert

I can't know whether that interpretation is correct, since I'm not the one who was given the assignment and any explanation that came with it.

[Nicholas]

Apologies for the delayed response, Here is the assignment and the information i was given.

[Nicholas]

This is all I've managed to do so far. I tried using a for loop

[DGM]

So from this we can tell that the image is to be black-on-white and numeric. We can also tell that none of these answers will meet the requirements. The assignment instructs to do it row-wise using a loop (as maddening as that sounds). The prior question I answered on this assignment used a loop. I'll leave it to you to find it.

As an aside, when given an assignment that explicitly tells me to do things the dumb inefficient way, I'd tend to do it the way I'm told, and then also do it in a better way just to point out the absurdity of teaching students how to shoot themselves in the foot. Of course, the TA grader didn't write the assignment, but it's the thought that counts -- and usually the TA knows it's BS too.