I want to save the result of ItemRenderer#renderGuiItem to a png file. How to do it? Is it even possible?

It's possible, but why do you want to do that?

21 minutes ago, ChampionAsh5357 said:

It's possible, but why do you want to do that?

I want to make a gui based on the CEF mod (chromium browser) and display item icons there

That sounds like the completely wrong way to do this.

You already have a .png file in the mod jar(s).

 

A quick look at the MCEF source code shows it has a mechanism to have custom urls (schemes) that you can use to reference minecraft assets.

There's even some code in their example mod

https://github.com/Mysticpasta1/mcef-forge/blob/51e69d97e4241501ec33f96d066176eb4c723fd1/src/main/java/net/montoyo/mcef/example/ExampleMod.java#L41

If you have problems adapting that example to your use case, talk to the mod author.

 

NOTE: The actual implementation of that example looks kind of horrible.

It should at least be using

Minecraft.getInstance().getResourceManager().getResource()

instead of Class.getResourceAsStream().

 

Edited September 7, 20223 yr by warjort

Correction:  I can see you wanting to use the ItemRenderer for items that have non-trivial models. 

You won't be able to use the raw pngs for them and some items like grass need colors applied to them.

 

I am not familiar with the processing to turn buffers into images.

But if I was going to do it, I would look at how Minecraft.grabPanoramixScreenShot() creates a NativeImage?

Obviously, you will be rendering just the item not the full Level. 🙂 

Edited September 7, 20223 yr by warjort