When Does "Adapting" An Image Go Too Far? I am interested in using a particular figure from the literature, but I do not want to go through the hassle of paying to use a figure. What I am wondering is if I made a similar figure, how easy is it to get in trouble for copyright infringement? If I were to essentially redo the image, it would not be verbatim the same, but very similar depictions would be pulled from the image. As an example, I provided two illustrative examples where the bottom image is an "adapted" version: 

The second one is in a published paper as well from a reputable journal, so I am guessing that it should be okay to go about making a similar diagram myself, but again, I wouldn't mind other opinions as too when I might start to tow the line on copyright infringement.
If this is for a book, rather than for a paper, you have another option. Many book publishers will give you a certain budget for paying royalties on figures and such. Another alternative, if you are to receive royalties from book sales is to have the publisher pay any fees up front and charge it against your future earnings on the book. The former is preferable, of course. But book publishers expect to have to pay for some things such as cover pictures and some internal figures. 

I doubt that this is an option for any journal, however.