Convert image pixels to XYZ-coordinates (3D plot)

Hello everyone,

I want to extend the following code:

Im = imread('./Images/Plot.png');
figure(1);
imshow(Im);
CoordinateMatrix = pic2points(Im);
scatter(CoordinateMatrix (:,1), CoordinateMatrix (:,2),'.');
figure(2);

so that:

- be able to display multiple images in the same graph (the images are in the "Images" folder that has been created; an example of an image is the one attached)

- display the graph in 3D (and not in 2D as in this case)

[Alberto Acri]

I changed the code in the following way but it only allows me to see a transformed figure with "pic2point".

myFolder = 'C:\Users\Alberto\Downloads\pic2points\Images';
if ~isdir(myFolder)
  errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
  uiwait(warndlg(errorMessage));
  return;
end
filePattern = fullfile(myFolder, '*.png');
jpegFiles = dir(filePattern);
for k = 1:length(jpegFiles)
  baseFileName = jpegFiles(k).name;
  fullFileName = fullfile(myFolder, baseFileName);
  fprintf(1, 'Now reading %s\n', fullFileName);
  imageArray = imread(fullFileName);
  % figure();
  imshow(imageArray);  % Display image.
  drawnow; % Force display to update immediately.
  figure(1);
  CoordinateMatrix = pic2points(imageArray);
  scatter(CoordinateMatrix (:,1), CoordinateMatrix (:,2),'.');
  figure(2);
end

[Alberto Acri]

I would like to open the images obtained at the end of the "pic2points" function into a single three-dimensional image.

Answer 1

[Image Analyst]

Try this:

myFolder = 'C:\Users\Alberto\Downloads\pic2points\Images';
if ~isfolder(myFolder)
    errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
    uiwait(warndlg(errorMessage));
    return;
end
filePattern = fullfile(myFolder, '*.png');
imageFiles = dir(filePattern);
for k = 1:length(imageFiles)
    baseFileName = imageFiles(k).name;
    fullFileName = fullfile(myFolder, baseFileName);
    fprintf('Now reading %s\n', fullFileName);
    imageArray = imread(fullFileName);
    CoordinateMatrix = pic2points(imageArray);
    scatter(CoordinateMatrix(:, 1), CoordinateMatrix(:, 2), '.');
    hold on;
end
fprintf('Done!\n');

[Alberto Acri]

OK, thanks for the help @Image Analyst. With your code I can correctly display the images separately.

Is it possible to display all the images I got in the same figure? Possibly with three dimensional visualization?

[Image Analyst]

I'm not exactly sure what z is. Maybe k? If so use plot3

Instead of

scatter(CoordinateMatrix(:, 1), CoordinateMatrix(:, 2), '.');

try

z = k * ones(size(CoordinateMatrix, 1), 1);
plot3(CoordinateMatrix(:, 1), CoordinateMatrix(:, 2),  z, '.');

Or see the attached demo.

[Alberto Acri]

Okay, the code works!

Is it also possible to put the created images in one plot3? As in attached figure.

[Image Analyst]

Everything should already be in the same axes. Nothing in my code creates a new axes or figure window.

Plus I also use "hold on" so it will just overwrite (add on) the additional plot curves to the existing axes.

[Alberto Acri]

I tried running the code again. I display the figures (.png) in separate images (plot3). I would like to "merge" them all into a single image as in the figure shown in the demo.

[Image Analyst]

Attach your script and 3 of your input images.

If you have any more questions, then attach your data and code to read it in with the paperclip icon after you read this:

TUTORIAL: How to ask a question (on Answers) and get a fast answer

[Alberto Acri]

Here is the code and 4 figures attached:

myFolder = 'C:\Users\Alberto\Downloads\pic2points\Images';
if ~isfolder(myFolder)
    errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
    uiwait(warndlg(errorMessage));
    return;
end
filePattern = fullfile(myFolder, '*.png');
imageFiles = dir(filePattern);

for k = 1:length(imageFiles)
    baseFileName = imageFiles(k).name;
    fullFileName = fullfile(myFolder, baseFileName);
    fprintf('Now reading %s\n', fullFileName);
    imageArray = imread(fullFileName);
    CoordinateMatrix = pic2points(imageArray);
    % scatter(CoordinateMatrix(:, 1), CoordinateMatrix(:, 2), '.');
    z = k * ones(size(CoordinateMatrix, 1), 1);
    plot3(CoordinateMatrix(:, 1), CoordinateMatrix(:, 2),  z, '.');
    hold on
end

[Image Analyst]

Try this

clc;    % Clear the command window.
fprintf('Beginning to run %s.m ...\n', mfilename);
close all;  % Close all figures (except those of imtool.)
clearvars;
workspace;  % Make sure the workspace panel is showing.
format short g;
format compact;
myFolder = pwd; %'C:\Users\Alberto\Downloads\pic2points\Images';
if ~isfolder(myFolder)
    errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
    uiwait(warndlg(errorMessage));
    return;
end
filePattern = fullfile(myFolder, '*.png');
imageFiles = dir(filePattern);
hFig3 = figure('Name', '3D Plot', 'NumberTitle', 'off');
for k = 1:length(imageFiles)
    baseFileName = imageFiles(k).name;
    fullFileName = fullfile(myFolder, baseFileName);
    fprintf('Now reading %s\n', fullFileName);
    imageArray = imread(fullFileName);
    drawnow;
    % Call pic2points.  This will open a new figure.
    CoordinateMatrix = pic2points(imageArray);
    % Switch to the figure for the 3-D plotting:
    figure(hFig3);
    % scatter(CoordinateMatrix(:, 1), CoordinateMatrix(:, 2), '.');
    z = k * ones(size(CoordinateMatrix, 1), 1);
    plot3(CoordinateMatrix(:, 1), CoordinateMatrix(:, 2),  z, '.');
    hold on
    drawnow;
end
grid on;
hFig3.WindowState = 'maximized';
fprintf('Done running %s.m.\n', mfilename);

[Alberto Acri]

OK, the code works.

Last clarification. Is it possible to apply the same color for all figures? And is it possible to change the position of each figure on the Z axis? In the graph: the first figure is placed on the plane with Z=1, the second figure on the plane with Z=2, etc. That is, a step=1 is imposed. I would like to define at which step to place the images.

[Image Analyst]

Yes, just specify the color in plot3(), for example if you want blue:

plot3(CoordinateMatrix(:, 1), CoordinateMatrix(:, 2),  z, 'b.');

Since it answered your question, could you please click the "Accept this answer" link?

Thanks in advance. 🙂

[Alberto Acri]

Thank you @Image Analyst! I will make another post to see if it is possible to set a step value to my liking.