Remapping problem in order to calculate the estimate of new frame

Question

NICOLE LONGHI 2023-10-23

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2037566-remapping-problem-in-order-to-calculate-the-estimate-of-new-frame

回答： Matt J 2023-10-23

I need to calculate the estimate of a new frame starting from frame1, and I need to use the process of remapping (the process of taking pixels from one place in the image and locating them in another position in a new image).

The function that allows me to do this is interp2, but on output it returns matrices of NAN (for the case of dst) or 0 (map_x and map_y). Does anyone know where I am going wrong or can suggest how to proceed? thank you very much

This is the code:

% Read the source image and convert it to double type.
img = im2double(imread('frame1.jpg'));
img_n = img(:, :, 1);
disp(size(img_n));
figure
subplot(211)
imshow(img);
title('3 channels');
subplot(212)
imshow(img_n)
title('2 channels');
% Initializes an empty target image and the two mapping matrices x and y
map_x = zeros(size(img_n), 'like', img_n);
map_y = zeros(size(img_n), 'like', img_n);
dst = zeros(size(img_n), 'like', img_n);
% Create a window to display the results
figure
remap_window = 'Remap demo';
imshow(dst);
title(remap_window);
% Initialize index for transformations.
ind = 0;
% Establish a cycle
while true
    % Update mapping matrices
    update_map(ind, map_x, map_y);
    
    % Apply the transformation using interp2
    dst = interp2(img_n, map_x, map_y);
    
    % Show result
    imshow(dst);
    
    % Wait for a key press or mouse click.
    c = waitforbuttonpress;
    if c == 1
        break; % Exit the while loop if a key is pressed
    end
end
% Function to update mapping matrices.
function update_map(ind, map_x, map_y)
[rows, cols] = size(map_x);
for i = 1:rows
    for j = 1:cols
        switch ind
            case 0
                if j > cols * 0.25 && j < cols * 0.75 && i > rows * 0.25 && i < rows * 0.75
                    map_x(i, j) = 2 * (j - cols * 0.25) + 0.5;
                    map_y(i, j) = 2 * (i - rows * 0.25) + 0.5;
                else
                    map_x(i, j) = 0;
                    map_y(i, j) = 0;
                end
            case 1
                map_x(i, j) = single(j);
                map_y(i, j) = single(rows - i);
            case 2
                map_x(i, j) = single(cols - j);
                map_y(i, j) = single(i);
            case 3
                map_x(i, j) = single(cols - j);
                map_y(i, j) = single(rows - i);
            otherwise
        end
    end
end
ind = mod(ind + 1, 4); % Update the index for the next iteration
end