I'm trying to take a screenshot and then save that in Item nbt with a byte array:

	@Override
	public ActionResult<ItemStack> onItemRightClick(World worldIn, EntityPlayer playerIn, EnumHand handIn)
	{
		if (!worldIn.isRemote)
		{
			ItemStack stack = new ItemStack(ModItems.PICTURE);

			NBTTagCompound nbt;
			if (stack.hasTagCompound())
			{
				nbt = stack.getTagCompound();
			} else
			{
				nbt = new NBTTagCompound();
			}

			BufferedImage screenshot = new ScreenShotHelper().createScreenshot(Main.mc.displayWidth,
					Main.mc.displayHeight, Main.mc.getFramebuffer());
			byte[] bytes = null;
			try
			{
				ByteArrayOutputStream baos = new ByteArrayOutputStream();
				boolean foundWriter;
				foundWriter = ImageIO.write(screenshot, "jpg", baos);
				assert foundWriter;
				bytes = baos.toByteArray();
			} catch (IOException e)
			{
				e.printStackTrace();
			}

			nbt.setByteArray("Picture", bytes);

			stack.setTagCompound(nbt);
		}
		
		return super.onItemRightClick(worldIn, playerIn, handIn);
	}

But I get the error:

java.util.concurrent.ExecutionException: java.lang.RuntimeException: No OpenGL context found in the current thread.
	at java.util.concurrent.FutureTask.report(Unknown Source) ~[?:1.8.0_192]
	at java.util.concurrent.FutureTask.get(Unknown Source) ~[?:1.8.0_192]
	at net.minecraft.util.Util.runTask(Util.java:54) [Util.class:?]
	at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:798) [MinecraftServer.class:?]
	at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:743) [MinecraftServer.class:?]
	at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:192) [IntegratedServer.class:?]
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:592) [MinecraftServer.class:?]
	at java.lang.Thread.run(Unknown Source) [?:1.8.0_192]
Caused by: java.lang.RuntimeException: No OpenGL context found in the current thread.
	at org.lwjgl.opengl.GLContext.getCapabilities(GLContext.java:124) ~[lwjgl-2.9.4-nightly-20150209.jar:?]
	at org.lwjgl.opengl.GL11.glPixelStorei(GL11.java:2155) ~[lwjgl-2.9.4-nightly-20150209.jar:?]
	at net.minecraft.client.renderer.GlStateManager.glPixelStorei(GlStateManager.java:806) ~[GlStateManager.class:?]
	at net.minecraft.util.ScreenShotHelper.createScreenshot(ScreenShotHelper.java:99) ~[ScreenShotHelper.class:?]
	at com.thebox.guac.items.ItemCamera.onItemRightClick(ItemCamera.java:53) ~[ItemCamera.class:?]
	at net.minecraft.item.ItemStack.useItemRightClick(ItemStack.java:234) ~[ItemStack.class:?]
	at net.minecraft.server.management.PlayerInteractionManager.processRightClick(PlayerInteractionManager.java:384) ~[PlayerInteractionManager.class:?]
	at net.minecraft.network.NetHandlerPlayServer.processTryUseItem(NetHandlerPlayServer.java:796) ~[NetHandlerPlayServer.class:?]
	at net.minecraft.network.play.client.CPacketPlayerTryUseItem.processPacket(CPacketPlayerTryUseItem.java:43) ~[CPacketPlayerTryUseItem.class:?]
	at net.minecraft.network.play.client.CPacketPlayerTryUseItem.processPacket(CPacketPlayerTryUseItem.java:9) ~[CPacketPlayerTryUseItem.class:?]
	at net.minecraft.network.PacketThreadUtil$1.run(PacketThreadUtil.java:21) ~[PacketThreadUtil$1.class:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_192]
	at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_192]
	at net.minecraft.util.Util.runTask(Util.java:53) ~[Util.class:?]
	... 5 more

Anyone know why? (I'm new to Java/Modding)

I fixed this by removing the "!" on "!worldIn.isRemote"

20 minutes ago, The Box said:

I fixed this by removing the "!" on "!worldIn.isRemote"

The screenshot should only happen on the client side; therefore, you want to check for the isRemote value being true.