You can do it with Apex.
If you have only 1 image in the text you can use the following sample code.
Contact c = [
SELECT Id, Picture__c
WHERE Id = :contactId
c.Picture__c = c.Picture__c.replace('<img', '<img style="height: 256px"');
Note: update SObject name and field name
This problem is caused by the EXIF extension in this article, combined with the fact that apparently image-rotation is, by default, 0deg, so any compliant browser isn't allowed to show the image right-side-up.
The only fix for this is to reorient the image properly by using an image manipulation algorithm capable of reordering the pixels in the file, such ...