Plotting colourful line over gray image whilst retaining colourbar information

Hi, I would like to plot a colourful trajectory on top of a grayscale image whilst retaining the colour information of the trajectory. For example with the data below, I would like to plot Data B over Image A. Without Data B turning gray and without making the colourbar represent the grayscaled image. Any help would be greatly appreciated!

%Image A
RGB = imread('peppers.png');
I = rgb2gray(RGB);
figure
imshow(I)

hold on

%Data B
x = 1:1000; 
y = x;
z = zeros(size(x));
lineColor = x; 
surface([x;x], [y;y], [z;z], [lineColor;lineColor],...
	'FaceColor', 'no',...
	'EdgeColor', 'interp',...
	'LineWidth', 8);
cc = colorbar();

Answer 1

[Prachi Kulkarni]

Hi,

To plot a color line over the grayscale image A, the image should be represented in RGB format even though the colors are in grayscale. For this you will need to add one line to your code.

Following is the modified code with one extra line.

%Image A
RGB = imread('peppers.png');
I = rgb2gray(RGB);
% -----------------------------------------------------
% Add this line to your code
I = cat(3,I,I,I);
% -----------------------------------------------------
figure
imshow(I)
hold on
%Data B
x = 1:1000; 
y = x; 
z = zeros(size(x));
lineColor = x; 
surface([x;x], [y;y], [z;z], [lineColor;lineColor],...
    'FaceColor', 'no',...
    'EdgeColor', 'interp',...
    'LineWidth', 8);
cc = colorbar();

[Manny Kins]

Thank you for your help! When I try to plot this, it seems that the plotted line isn't showing it's full spectrum of colours (all the way up to yellow), do you think this is because the RGB image background is interfering with the colorbar? Thanks

[Prachi Kulkarni]

Hi,

The color line is not showing the full range of colors, because the color is ranging from 1 to 1000, but the line is stopped at 384 due to the size of the grayscale image.

To get the full range of colors, x will have to range from 1 to the smallest dimension of the grayscale image, which is 384 in this case.

Following is the modified code.

%Image A
RGB = imread('peppers.png');
I = rgb2gray(RGB);
% -----------------------------------------------------
% Add these lines to your code
lineLength = min(size(I));
I = cat(3,I,I,I);
% -----------------------------------------------------
figure
imshow(I)
hold on
%Data B
% -----------------------------------------------------
% Modify this line in your code
x = 1:lineLength; 
% -----------------------------------------------------
y = x;
z = zeros(size(x));
lineColor = x; 
surface([x;x], [y;y], [z;z], [lineColor;lineColor],...
    'FaceColor', 'no',...
    'EdgeColor', 'interp',...
    'LineWidth', 8);
cc = colorbar();

[Manny Kins]

Many thanks for your help and explanation and sorry for the late response! Take care