Save render in multiple formats with one button (or script)?
In the Compositor you can have as many File Output nodes as you like, with each one set to different file type parameters, different OpenEXR multilayers, etc. So just add one for each of your outputs, set the node properties appropriately, and wire up the appropriate render layer(s) to the Image inputs.
You can even have render layers drawn from multiple scenes and it will render whatever it needs to produce the “comp”. You can setup a separate compositing scene that just serves to drive your different scene renders and produce all the appropriate outputs (for a complex project).
Well, I thought of it, but how to initiate saving files when you cancel the render by pressing the escape key (when the noise level, for example, at an acceptable level)? Because when the render ends, the save occurs, but when the rendering is stopped, the save does not happen (it seems the blender regards this as "this bad render, I will not save it)?
Yeah, the usual suggestion here seems to be to save the resulting image as an EXR, and then use a separate compositing .blend (or maybe just scene) to input the EXR and do your comp/outputting.
how to initiate saving files when you cancel the render by pressing the escape key (when the noise level, for example, at an acceptable level)?
If you’re doing an F12 render in Progressive Refine mode and you stop it, in 2.79 you can hit F3 in the image viewer to save the image. In 2.80 it’s SHIFT-S I believe from the new render window display (assuming the default Render Display Mode settings).
P.S. Progressive Refine is usually at least 2x slower then regular tile-based rendering, and it is incompatible with the Blender Denoise feature currently. Also support for progressive renders is apparently not a focus of the Blender developers as they don’t see it as being very important.
So you’ll likely be able to get better results faster if you figure out what the “right” number of samples is, and often using Denoise can reduce the required number of samples and render time by a huge factor.