Triangle Circle Dataset Creation

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marsmar 2022-11-15

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https://ww2.mathworks.cn/matlabcentral/answers/1852038-triangle-circle-dataset-creation

编辑： DGM 2022-11-26

I need to generate a triangle in matlab in the scope of 500x500 pixels. I need to generate a certain amount of images so its a dataset. The triangles either need to be at a certain angle and be either pink or purple. I have no idea what commands to use.

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DGM 2022-11-15

What are the constraints?

Do they need to be a certain configuration? Irregular? Regular?
How many triangles per image?
Do they need to be a certain size?
Do they need to be in a certain position?
Can they intersect image boundaries?
What's the background?
Are the triangles supposed to be a particular pink/purple, or can it be any random color in that range?
Do the triangles need to be binarized, or should they be antialiased?

marsmar 2022-11-25

They can be irregular or regular! I just need one triangle per image and they just need to be within the 500x500 pixels. They can be in any position and it could vary. The background by default is white. They can be in any random color range.

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Answer 1

DGM 2022-11-16

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https://ww2.mathworks.cn/matlabcentral/answers/1852038-triangle-circle-dataset-creation#answer_1101043

在 MATLAB Online 中打开

Until clarification, here's a crude example.

% some parameters, maybe?

szo = [500 500]; % [y x]

fgcolor = [0.7 0.3 1];

bgcolor = [0 0 0.2];

% does any of this need to be fixed? random?

% this will use a fixed radius

% but angles and center are contrained random

r = 100;

center = (szo-2*r-1).*rand(1,2)+1+r; % [y x]

angles = 0:120:240;

angles = angles + 10*rand() + 10*randn(size(angles));

angles = [angles angles(1)];

x = r*cosd(angles) + center(2);

y = r*sind(angles) + center(1);

% create a mask

mask = poly2mask(x,y,szo(1),szo(2));

% create the ouput image (no antialiasing)

outpict = repmat(permute(bgcolor,[1 3 2]),szo);

outpict = mask.*permute(fgcolor,[1 3 2]) + (1-mask).*outpict;

outpict = im2uint8(outpict);

imshow(outpict)

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DGM 2022-11-17

编辑：DGM 2022-11-19

在 MATLAB Online 中打开

Here's another blind tangent. If I'm just guessing in the dark, I'm not going to go out of my way to avoid MIMT tools. I doubt this is what you want, but right now, you're the only person who can know that.

% some parameters, maybe?
szo = [500 700]; % [y x]
fgcolorlim = [0.8 0.3 1; 1 0.3 0.5];
bgcolor = [0 0 0.2];
rlimits = [75 150]; % allowed range of vertex radius
maxrotation = 60; % maximum nominal rotation
anglevariance = 10; % variance of individual vertex angles
margins = -50; % how far to keep triangles from border
fgCT = makect(fgcolorlim(1,:),fgcolorlim(2,:),64); % create color table
outpict = repmat(permute(bgcolor,[1 3 2]),szo); % create colored BG
for k = 1:20
    % get constrained random vertex coordinates	
    r = randrange(rlimits,1);
    margins = min(margins,szo/2 - r); % margins must leave no less than zero area
    center = (szo-2*(r+margins)-1).*rand(1,2)+1+r+margins; % [y x]
    angles = 0:120:240; % nominal vertex angles
    angles = angles + maxrotation*rand() + anglevariance*randn(size(angles)); % rotate, perturb
    angles = [angles angles(1)]; %#ok<AGROW> % close polygon
    x = r*cosd(angles) + center(2);
    y = r*sind(angles) + center(1);
    
    % create a mask
    mask = poly2mask(x,y,szo(1),szo(2));
    
    % create the ouput image
    fgcolor = fgCT(randi([1 size(fgCT,1)],1,1),:); % a random color from the CT
    alpha = randrange([0.2 0.8],1); % pick random opacity
    outpict = replacepixels(fgcolor,outpict,alpha*mask);
end
outpict = im2uint8(outpict);

makect(), randrange(), replacepixels() are from MIMT on the FEX.

DGM 2022-11-25

在 MATLAB Online 中打开

randrange.m

So long as the shapes are polygons, all that's needed is a change to the nominal vertex angle list.

% some parameters, maybe?

szo = [500 500]; % [y x]

fgcolor = [0.7 0.3 1];

bgcolor = [0 0 0.2];

nvert = 5; % number of vertices

rlimits = [75 150]; % allowed range of vertex radius

maxrotation = 60; % maximum nominal rotation

anglevariance = 0; % variance of individual vertex angles

margins = 0; % how far to keep triangles from border

% generate vertices

r = randrange(rlimits,1);

margins = min(margins,szo/2 - r); % margins must leave no less than zero area

center = (szo-2*(r+margins)-1).*rand(1,2)+1+r+margins; % [y x]

angles = 0:360/nvert:(360-360/nvert); % nominal vertex angles

angles = angles + maxrotation*rand() + anglevariance*randn(size(angles)); % rotate, perturb

angles = [angles angles(1)]; % close polygon

x = r*cosd(angles) + center(2);

y = r*sind(angles) + center(1);

% create a mask

mask = poly2mask(x,y,szo(1),szo(2));

% create the ouput image (no antialiasing)

outpict = repmat(permute(bgcolor,[1 3 2]),szo);

outpict = mask.*permute(fgcolor,[1 3 2]) + (1-mask).*outpict;

outpict = im2uint8(outpict);

imshow(outpict)

marsmar 2022-11-25

I have an error with the "randrange" function. Is it a function specific to a certain toolbox? I'm trying to recreate a square and had just edited the "nvert" number to 4.

DGM 2022-11-26

编辑：DGM 2022-11-26

在 MATLAB Online 中打开

I attached randrange(). It's just a convenience tool that I used and didn't bother removing. It's basically just one line. You could also simply just replace the one where it's used with

r = rlimits(1) + rand()*range(rlimits);

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Answer 2

David Hill 2022-11-15

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1852038-triangle-circle-dataset-creation#answer_1101033

Look at polyshape

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