I wasn’t talking about a woman dressed in an extremely immodest way. A picture should be discussed separately.

Was it ruled in the Shulchan Arukh and in Maimonides in accordance with this view, that the secondary prohibitions require one to die rather than transgress?

I don’t think it appears in the Shulchan Arukh. But in Maimonides, yes.
See sources here: http://shut.moreshet.co.il/shut2.asp?id=41545

To look at an immodestly dressed woman under coercion is considered one of the secondary prohibitions? It is not at all clear that there is even a source forbidding looking at an immodestly dressed woman [without lustful thoughts about her, and without intending to enjoy her beauty, because that one cannot be forced to do], and then to define this as one of the secondary prohibitions?
All the more so, a picture is not even in the category of “nakedness” at all, but merely a drawing.

If you can look without lustful thoughts, maybe you’re right. I wonder how many stone-made people like you there are here?

Hahaha

Looking at a picture is a question of lustful thoughts that may lead to wasting seed, not of the secondary prohibitions of sexual immorality. There is certainly no obligation of self-sacrifice in order not to waste seed

I’m warning about this even without someone putting a gun to your temple. See, for example, yeshivot and what happens among them because of this. You can learn from the deeds of the righteous Rabbi Leibowitz, who read pornographic books and talked about Marilyn Monroe with drool on his lips.

Anyone who tells you that you have to die over an immodest picture deserves to have a gun put to his temple because of bloodshed.

Forbidden sexual relations means relatives.