Enforcing maximum image width in a table

We have a Confluence page that contains a Jira macro; the macro outputs a tables that includes fields from the Jira issue.  Some of the Jira description fields include images.

When this page is exported to PDF, the macro is exported as a table, but we have an issue sizing the images.

By default, they are set such that they fill 100% of the cell; this is bad for the smaller images which get enlarged and lose resolution.

I can ensure that they are set to their natural size by specifying:

table img {

    width: auto !important;
}

This ensures they are not re-scaled, but it means that the larger images overrun.

To prevent this, I have added a max-width to the CSS, but it turns out this does not affect table cell contents (it's just ignored).

For the record, I also fix the column widths and set table-layout to fixed as shown below.

td:nth-child(1).jira-macro-table-underline-pdfexport * {

width: 3cm !important;
}

td:nth-child(2).jira-macro-table-underline-pdfexport * {
width: 3cm !important;
}

td:nth-child(3).jira-macro-table-underline-pdfexport * {
width: 13cm ;
}

td:nth-child(4).jira-macro-table-underline-pdfexport * {
width: 4cm !important;
}

table {
table-layout:fixed !important;
}

table img {

width: auto !important;
max-width: 10cm !important;

}

 It seems that it's actually part of the CSS spec that max-width doesn't apply to table contents, but some sites suggest setting the display parameter (e.g. to block) for the image elements in the table.

Any ideas?

Thanks,

Guy.