How to keep all image data after transformation?
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In the below code, I try to calculate the distance between the 1-pixel and the other 0's pixels within a4 matrix. I face a problem because the 1-pixel is disappeared from the matrix after transformation, therefore, the err4 values becomes inf for all.
h = 120;
v = 80 ;
r=20;
row = 200;
col = 300;
T = [1 0 0;
0 1 0;
h v 1];
tform = affine2d(T);
%create mask
a4 = zeros(row,col);
%set one control point (cp) for mask
a4(row/5*4,col/5*4) = 1;
cb_ref = imref2d(size(a4));
%Apply transformation same as ourput floating image.
b4 = imrotate(a4,r);
b4 = imwarp(b4,tform,'OutputView', cb_ref); % refrence space relative with another image.
%calculte the error matrix
err4 = bwdist(b4);
How can allow the matrix to grow after transformation to keep the 1-pixel?
5 Comments
Image Analyst
on 3 Mar 2018
That doesn't help. Without code to define cb_ref, we can't run your code, and the comments aren't enough for me to figure out what's happening. So all I can say now is to make sure that b4 is a 2-D logical (binary) image.
Answers (1)
Image Analyst
on 4 Mar 2018
I don't know what your plans are for the warping, but after you warped the image, the dot disappeared:
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 15;
h = 120;
v = 80 ;
r=20;
row = 200;
col = 300;
T = [1 0 0;
0 1 0;
h v 1];
tform = affine2d(T);
%create mask
a4 = zeros(row,col);
%set one control point (cp) for mask
a4(row/5*4,col/5*4) = 1;
% Display the image.
subplot(2, 2, 1);
imshow(a4, []);
title('a4 Image', 'FontSize', fontSize, 'Interpreter', 'None');
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0, 0.04, 1, 0.96]);
% Apply transformation same as output floating image.
b4 = imrotate(a4, r);
% Display the image.
subplot(2, 2, 2);
imshow(b4, []);
title('b4 Image', 'FontSize', fontSize, 'Interpreter', 'None');
cb_ref = imref2d(size(a4));
b4 = imwarp(b4, tform, 'OutputView', cb_ref); % reference space relative with another image.
% Calculate the error matrix
% Display the image.
subplot(2, 2, 3);
imshow(b4, []);
title('b4 Warped Image', 'FontSize', fontSize, 'Interpreter', 'None');
err4 = bwdist(b4);
% Display the image.
subplot(2, 2, 4);
imshow(err4, []);
title('err4 Image', 'FontSize', fontSize, 'Interpreter', 'None');
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/179636/image.png)
7 Comments
Image Analyst
on 6 Mar 2018
But it's new position is not in the image. You did something after rotation so that the point is not there. That's what my demo showed.
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