Ladies camisoles are usually expensive and full of artificial fiber bits. Cotton T-shirts are too much for me to wear under the button shirts that I normally wear all summer to keep the sun off me. One day a friend gave me the pink shirt in the first picture and it's really comfortable and does exactly what I wanted. Then I got the idea of cutting up some T-shirts in the back of my drawer to make my own. I use the pink one as a pattern, drawing a seam allowance, then cut it out.
There are a couple of books called "Generation T" which have a bunch of patterns and ideas around re-using T-shirts. All manner of other clothes, bags, accessories, etc. The beauty of T-shirt fabric is that it does not easily fray along a cut edge, so a lot of things can be done with no sewing at all, but only cutting and perhaps tying together long strips or ends. At various farms I have been on, it was common for women to make halter tops and tank tops out of T-shirts this way.