Constant subplot size and variable figure size

I have a script that processes some surface scans. The number of files I'm processing can vary each time (from 1 to ~40). I am currently using this FE to minimize the space between each subplot.

However, I'm also outputting text on top of the surface plot, and when the number of files increases, I am forced to increase the number of rows and reduce the text size (and position) to keep everything aligned properly.

What I'd ideally like to have is a fixed size for each subplot (say, 800x800 points, font size 26 for all text annotations), and then have the figure expand beyond my screen size to accomodate more subplots -- for example, when processing 30 files I would get a 5x6 array of subplots all sized 800x800. This figure would then be exported as an image and I can resize for other uses.

I've attached an image with my intended output depending on the number of files. In each case, the individual subplot sizes and text annotations should remain the same.

[Rik]

If you're going to export as image anyway, why not go all the way and generate each tile separately? Then you can either combine them (e.g. with montage) in Matlab, or put them together in whatever software you were going to use next.

[MH]

I didn't know about montage but can give it a try. I assume the process would be to plot each figure, export it as an image, then montage the set of images?

[Rik]

The montage function can be used to 'unstack' a 3D variable, which is very useful for CT, MRI, and (S)PE(C)T scans. The input is a variable with rows*col*color*page:

load mri % example included in the IPT
size(D)

ans = 1×4

128 128 1 27

montage(D)

For more usage details, see the doc.

[MH]

Thanks Rik. This is what my code looks like now, and it works relatively well.

Is there a way to optimize this so that I don't have to save 20 images? I looked into a function to montage a set of open figures, but the only one I found was this and it requires a lot of additional tweaking to get the padding/spacing right.

clear all
clc

matSize = 800;

curDir = pwd;

[X,Y,Z] = peaks(matSize);

rows = 2;
cols = 3;

for i=1:rows*cols
    myFig = figure('visible','off');
    set(myFig,'units','points','outerposition',[0 0 matSize matSize]);
    surf(Z,'LineStyle','none');
    axis equal
    axis off
    colormap jet
    view(2)
    text('Position',[0.4 0.5],'units','normalized','String','text','FontSize',32)
    figStr = strcat('image',num2str(i),'.tif');
    figStr = fullfile(curDir,figStr);
    exportgraphics(myFig,figStr,'BackgroundColor','white','ContentType','image','Resolution',200)
    close(myFig)
end

fileFolder = fullfile(pwd);
dirOutput = dir(fullfile(fileFolder,'*.tif'));
fileNames = string({dirOutput.name});
h = montage(fileNames, 'Size', [rows cols],'ThumbnailSize',[]);
montage_IM=h.CData;
imwrite(montage_IM,'montage.tif');

[Rik]

This is about what I would do.

You could improve this by moving the figure creation out of the loop and modify the properties of the graphics object inside your loop. You could also read (and delete) the image file in your loop and store the result in a 3D array. You can use permute(I stack,[1 2 4 3]) to make sure the image is the shape montage expects. (I didn't know it supported entering filenames BTW)

Answer 1

[MH]

Per Rik's suggestion, I've incorporated montage to produce the final desired result. If anyone has suggestions on how to further optimize this code (or another method that would produce the same result) please do chime in.

Note that the code below is just a sample snippet, so I've eliminated a lot of the user input and gui code.

matSize = 800;
curDir = pwd;
numOfFiles = 6;
[X,Y,Z] = peaks(matSize);

rows = 2;
cols = 3;

A = cell(numOfFiles);

for i=1:numOfFiles
    myFig = figure('visible','off');
    set(myFig,'units','points','outerposition',[0 0 matSize matSize]);
    surf(Z,'LineStyle','none');
    axis equal
    axis off
    colormap jet
    view(2)
    text('Position',[0.4 0.5 1],'units','normalized','String','My Text','FontSize',32)
    figStr = strcat('image','.tif');
    figStr = fullfile(curDir,figStr);
    exportgraphics(myFig,figStr,'BackgroundColor','white','ContentType','image','Resolution',200)
    A{i} = imread('image.tif');
    delete('image.tif');
    close(myFig);
end

figure
h = montage(A,'Size',[rows cols],'ThumbnailSize',[]);
montage_IM=h.CData;
imwrite(montage_IM,'montage.png');

[Rik]

I would still move some things out of the loop. I'm not sure how much I should suggest, as this is example code, but this would be a good start.

matSize = 100;%changed for the run-in-browser
curDir = pwd;
numOfFiles = 6;
[X,Y,Z] = peaks(matSize);

rows = 2;
cols = 3;

%initialize figure
A = cell(numOfFiles);
myFig = figure('visible','off');
set(myFig,'units','points','outerposition',[0 0 matSize matSize]);
h_surf=surf(Z,'LineStyle','none');
axis equal,axis off,colormap jet,view(2)
h_txt=text('Position',[0.4 0.5 1],'units','normalized','String','My Text','FontSize',32/8);
%        changed font size
figStr = strcat('image','.tif');
figStr = fullfile(curDir,figStr);
for n=1:numOfFiles
    set(h_surf,'XData',X,'YData',Y,'ZData',Z)
    set(h_txt,'String',sprintf('it %d',n))
    drawnow;%force graphics update
    exportgraphics(myFig,figStr,'BackgroundColor','white','ContentType','image','Resolution',200)
    A{n} = imread(figStr);
end
delete(figStr);
close(myFig);
    
figure
h = montage(A,'Size',[rows cols],'ThumbnailSize',[]);

montage_IM=h.CData;
imwrite(montage_IM,'montage.png');

[MH]

Thanks Rik, I'll incorporate some of the changes you suggested; it otherwise seems to be working really well for my purpose. And it's certainly more flexible than what I was doing previously (scaling font size based on the number of images being displayed).

Answer 2

[Adam Danz]

I used to use that file exchange function and it has been very useful but tiledlayout is now the better option. Here's a summary updated features to tiledlayout that allows you to control spacing.

After creating the subplots, change the units from normalize to points if you want the axis sizes to stay the same when the figure size changes.

Partial demo:

fig = figure(); 
tlo = tiledlayout(fig,6,6,'TileSpacing','none'); % [num rows, num cols]

tileorder = [1,7,8,13,14,15,19,20,21,25:36]; % row-wise

ax = gobjects(size(tileorder)); 
for i = 1:numel(tileorder)
    ax(i) = nexttile(tileorder(i));
end
box(ax,'on')
set(ax,'xtick',[],'ytick',[])

[MH]

Adam,

I had tried tiledlayout, but was never able to get the spacing to look as I wanted. It seems like the updates do help in this regard.

My issue is that this method still only works as long as the # of rows and/or cols is small enough for the plot sizes to fit on my screen. I've attached my sample code and the resulting outputs.

For 1 plot (or even 2 or 3) this works fine. But as the number of subplots grows, the font size would need to be scaled, which I don't want. I would ideally just define the look of 1 subplot (size, text, font size, position, etc) and have that tile repeat regardless of screen size.

clear all
clc

matSize = 800;

[X,Y,Z] = peaks(matSize);

rows = 1;
cols = 1;

myFig = figure;
h = tiledlayout(rows,cols,'TileSpacing','none','Padding','tight');

for i=1:rows*cols
    nexttile
    surf(Z,'LineStyle','none')
    axis equal
    axis off
    colormap jet
    view(2)
    text('Position',[0.4 0.5],'units','normalized','String','text','FontSize',32)
end

set(myFig,'units','points','outerposition',[0 0 matSize*cols*0.9 matSize*rows]);

[Adam Danz]

I've updated my answer to recreate the subplot layout in the image you shared.

I'm not sure I understand the spacing issues you're describing in your comment above. I only see 1 pair of axes, too.

[MH]

Sorry if my image was confusing.

What I was trying to convey is that if I have 1 file to process, the matrix will be, for example, 800x800; thus I would want the output image to be 800pts x 800pts, with text overlaid at a font size of 26.

But if the # of files I'm processing is such that 800*numOfFiles > screen resolution, what ends up happening is the tile gets resized to something smaller than 800x800 pts, and the font size of 26 is now too large and needs to be scaled.

The solution that Rik suggested with using the montage seems to work well, but it does come at the cost of having to generate a figure, output an image file, read the file to an array, delete the file, then montage everything in that array. With the tiledlayout, once the plotting is done the image can be exported once and is done.