How do you create a test image containing a ramp edge?

This is the ideal solution

this is my solution with the following (amateur approach) code:

I = uint8(zeros(40,150));
I(:,100:150) = 128;

X2=uint8(0:49);
X3=uint8(50:99);
Y=uint8(0:39);
I(:,50:99)=meshgrid(X2,Y);
I(:,100:149)=meshgrid(X3,Y);

figure, imshow(I), title("ramp edge")

Answer 1

[DGM]

Here's one way.

outpict = zeros(1,150,'uint8'); % a blank vector
outpict(50:99) = linspace(0,128,50); % add a linear ramp in the middle
outpict(100:end) = 128; % fill the end
outpict = repmat(outpict,[40 1]); % replicate it

imshow(outpict)

Here's a different way:

outpict = linspace(0,150*128/50,150); % a 1D linear ramp at the appropriate slope
outpict = min(outpict-49*128/50,128); % truncate it
outpict = uint8(repmat(outpict,[40 1])); % replicate it

imshow(outpict)

Or if you're using MIMT, you can just do

outpict = lingrad([40 150],[0 1/3; 0 2/3],[0; 128],'linear','uint8');

imshow(outpict)

... which is generally more flexible.

See also:

https://www.mathworks.com/matlabcentral/answers/532843-how-to-create-a-blue-color-gradient#answer_1092768