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Recode MATLAB generated images so they get picked up as thumbnails #21

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Merged
wkearn merged 1 commit into from
Mar 19, 2026
Merged

Recode MATLAB generated images so they get picked up as thumbnails #21

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21 changes: 20 additions & 1 deletion buildfile.m
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Original file line number Diff line number Diff line change
Expand Up @@ -55,7 +55,26 @@ function docsTask(~)
nb = fullfile(path, name+".ipynb");

fprintf("Rendering %s as %s\n", mlx, nb)
export(mlx, nb, Run=true);
export(mlx, nb, Run=true, FigureFormat="png");

% MATLAB currently (R2025b) exports embedded images in output cells
% with the text/html mimetype. The images are embedded in <img> tags
% with a data URL. This jq (https://jqlang.org/) filter extracts the
% data from this URL and replaces the "text/html" object in the output
% data with an "image/png" one. This works, but depends on how MATLAB
% chooses to export Jupyter notebooks. Bad things will also happen if
% any other output cells have the text/html mimetype.
jqfilter = ['''.cells[].outputs[]?.data |= if has("text/html") then ' ...
'{"image/png" : [."text/html"[] | ' ...
'capture("data:image/png;base64,(?<x>[A-Za-z0-9/=+]*)\"").x]} ' ...
'else . end'' '];
% jq will by default print colored output, which gets stored as ANSI
% escape codes. The -M option turns this off.
[status, cout] = system(['jq -M ' jqfilter char(nb)]);
if status ~= 0
error("jq unable to recode images: [%s] %s", status, cout);
end
writelines(cout, nb);
end

end