Vectorisation for nested for loops in Piecewise Linear Transformation

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Hi everyone,
I'm trying to remove the for loops in this piecewise linear transformation function and have tried using vectorisation but can't wrap my head around how the code would look.
for i = 1:size(original,1)
for j = 1:size(original,2)
if (original(i,j) < x1)
transformed(i,j) = m1 * original(i,j);
elseif (original(i,j) >= x1 && original(i,j) < x2)
transformed(i,j) = m2 * (original(i,j) - x1) + y1;
else
transformed(i,j) = m3 * (original(i,j) - x2) + y2;
end
end
end
Is there any way I can do a piecewise linear transformation (contrast stretching) without the nested for loop to speed up the execution?

Accepted Answer

Voss
Voss on 10 Nov 2022
transformed = original;
idx = original < x1;
transformed(idx) = m1 * original(idx);
idx = original >= x1 & original < x2;
transformed(idx) = m2 * (original(idx) - x1) + y1;
idx = original >= x2;
transformed(idx) = m3 * (original(idx) - x2) + y2;

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