Can anyone give me a link to a good free software enabling me to take a UK passport photo of my wife who at this time is unable to get out?

You don't need any software. You can take a picture with any camera, print it out, and go make your wife a passport. Go to the link for the full requirements, https://www.gov.uk/photos-for-passports

The one non-regular thing you need is paper. Photos printed on standard paper are not accepted. You'd be best off taking the photo yourself (according to the criteria in the link provided), ave it developed, and then cut it to size. Cutting must be done real nice.

Go to the gov site where are all the demands to passport photos are - check the size demands, learn how definitely she should sit and make up her hair for the photo, because often women are asked to give photos for passports with the hair behind the ears. After that make a picture and edit it with paint (if you are on windows) or with iPhoto (if you have a mac os) and you are done! Just select the size you need, both paint and iPhoto allow you do that.

How did I know someone would give a stupid reply to my question. Who said it was for a Passport? There are many things that require a Bona Fide sized Passport picture. Think before you answer.

If she cannot get out why would she need a passport

A camera ? if not what do you want. You can upload to your computer and size it. I am ancient and I do it.

UK