Add custom x and y axes (not relevant to the image)

Hi

I have an image with a 40x40 cm Field of View.

The image itself is a 432x432 pixel image so my workaround was to try scale the image by multiplying the values by 0.1, but it's not an ideal solution as it doesn't scale perfectly (using a scaling factor of 0.09259259259 ruins the axis) and also the axes dont start from the same zero point.

Is it possible to set a custom axes on the image to show 0-40 on the x and y axes? (instead of 40-0 on the y axis at the moment, reversing the axis currently flips the image).

conversion=0.1; % in cm/pixel
addMMx=@(x) sprintf('%1d',x*conversion);
addMMy=@(y) sprintf('%1d',y*conversion);

xticklabels(cellfun(addMMx,num2cell(xticks'),'UniformOutput',false));
yticklabels(cellfun(addMMy,num2cell(yticks'),'UniformOutput',false));
xlabel('cm')
ylabel('cm')
h = colorbar;
set(h,'YTick',[])
ylabel(h, 'Relative Temperature');

Answer 1

[Rik]

The code below should help. You can specify tick labels that have nothing to do with the ticks themselves.

%start out with a clean figure
figure(1),clf(1)

%get an example image to work with
h=image;im=h.CData;im=imresize(im,10);

%create the plot itself
imshow(im),colormap('jet')
caxis([0 32])%adjust color axis to fit the image
axis on

%calculate the locations of the ticks and the appropriate labels
FOV=40;
cm_ticks=0:5:40;
px_ticks_x=linspace(0.5,size(im,1)+0.5,numel(cm_ticks));
px_ticks_y=linspace(0.5,size(im,2)+0.5,numel(cm_ticks));
ticklabels=cellfun(@(v) sprintf('%d',v),num2cell(cm_ticks),...
    'UniformOutput',false);

%apply ticks and custom ticklabels
set(gca,'XTick',px_ticks_x)
set(gca,'XTickLabels',ticklabels)
set(gca,'YTick',px_ticks_y)
set(gca,'YTickLabels',ticklabels(end:-1:1))

xlabel('cm')
ylabel('cm')

h = colorbar;
set(h,'YTick',[])
ylabel(h, 'Relative Temperature');

[James Blackwell]

Hi Rik!

Works great, thanks for that!

[José Anchieta de Jesus Filho]

Hey guys. I am trying to adapt this script to my situation, could you help me?

This image, let's say it is 571x1053 pixels. I want the x axis to be between -35 and 35 (for example x = -35: 10: 35) in the matlab and the y axis to be between 0 and 30 (for example y = 0:10:30). How would I do this adaptation?

%get an example image to work with
h=imread('pic.jpg');

%get an example image to work with

h1=image(h);im=h1.CData;im=imresize(im,10);
imshow(im),colormap('jet')
axis on
%calculate the locations of the ticks and the appropriate labels

cm_ticks=-35:10:35;
cm2_ticks=0:10:30;

px_ticks_x=linspace(0.5,size(im,1)+0.5,numel(cm_ticks));
px_ticks_y=linspace(0.5,size(im,2)+0.5,numel(cm2_ticks));
ticklabels=cellfun(@(v) sprintf('%d',v),num2cell(cm_ticks),...
    'UniformOutput',false);
ticklabels2=cellfun(@(v) sprintf('%d',v),num2cell(cm2_ticks),...
    'UniformOutput',false);
%apply ticks and custom ticklabels
set(gca,'XTick',px_ticks_x)
set(gca,'XTickLabels',ticklabels)
set(gca,'YTick',px_ticks_y)
set(gca,'YTickLabels',ticklabels2(end:-1:1))
xlabel('mm')
ylabel('mm')
h = colorbar;
set(h,'YTick',[])
ylabel(h, 'magnetic field densisty');

[Rik]

@José Anchieta de Jesus Filho Have a read here and here. It will greatly improve your chances of getting an answer.

It is not immediately obvious to me how your question relates to this question. Please post it as a separate question thread. Feel free to post a link in this thread.

[José Anchieta de Jesus Filho]

Hello Rik

https://www.mathworks.com/matlabcentral/answers/804141-custom-axis-at-the-imshow