How do I randomize an NPC object sprite color palettes onDraw while rotating? (solved)

[cato]

Currently, I have the horizontal sprite sheet of an NPC object (1 frame) with the others being the same but different color palettes next to the original one. In my custom NPC Lua file, I can't seem to have it randomize the starting color and rotate simultaneously.

I have tried once or twice just randomizing the color (without the rotation) in the onDraw function. I used a random value to determine where the image should source from (in terms of pixels). However, either the NPCs were stuck with one color at a time or the NPC is flashing like a Disco shell.

I did get the rotation to work (thanks to SetaYoshi's wormhole) in terms of creating a sprite. The problem is that I can't try the same with the color randomization. When I override the sprite sheet, it stretches to the object's size (32x32) instead of sourcing the sprite from a particular position. Besides that, I am unable to come up with where I should put my randomizer in (especially the sourceX part), as well as some other details between the sprite initialization and the onDraw function. Putting the parts in either places don't do anything.

Here is the NPC Lua code in question:

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local npcManager = require("npcManager")
local npcutils = require("npcs/npcutils")
local rng = require("rng")

-- Settings
-- Harmtypes

local iniNPC = function(v)
	local config = NPC.config[v.id]
	if not v.data.ini then
	  	v.data.ini = true
		v.data.sprite = Sprite.box{
			x = v.x,
			y = v.y,
			width = 32,
			height = 32,
			texture = Graphics.sprites.npc[v.id].img,
			rotation = 0,
			align = Sprite.align.CENTRE,
			frames = npcutils.getTotalFramesByFramestyle(v)
		}
	end
end

function myNPC.onTickEndNPC(v)
	iniNPC(v)
	v.data.sprite:rotate(12 * v.direction)

        -- NPC behaviors
end

function myNPC.onDrawNPC(v)
	if v:mem(0x12A, FIELD_WORD) <= 0 then
        return end

	local config = NPC.config[v.id]
	local p = -45

	if config.foreground then	p = -15	end
	v.data.sprite.x = v.x + v.width*0.5 + config.gfxoffsetx
	v.data.sprite.y = v.y + v.height*0.5 + config.gfxoffsety
	v.data.sprite:draw{priority = p - 0.1, sceneCoords = true, frame = v.animationFrame + 1}

	npcutils.hideNPC(v)
end

return myNPC;

And the lines/parts I probably needed to add:

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local smallballs = Graphics.loadImageResolved("smallballs.png")
Graphics.sprites.npc[752].img = Graphics.loadImage("smallballs.png")
local state = rng.randomInt(0, 7)
sourceX = 32 * state

Many thanks to someone who can help. And I am definitely keeping this useful stuff for future uses.

[deice]

i'd say your biggest issue is the fact that the sprite sheet is horizontal. if you rotate it 90 degrees in an image editor, you could use the following simple solution:

1. load "smallballs"

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local smallballs = Graphics.loadImageResolved("smallballs.png")

(at the start of the file)

2. replace your current "iniNPC" with:

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local iniNPC = function(v)
	local config = NPC.config[v.id]
	if not v.data.ini then
	  	v.data.ini = true
		v.data.color = rng.randomInt(0, 7)
		v.data.sprite = Sprite.box{
			x = v.x,
			y = v.y,
			width = 32,
			height = 32,
			texture = smallballs,
			rotation = 0,
			align = Sprite.align.CENTRE,
			frames = 8
		}
	end
end

3. then in onDrawNPC, replace the draw call with:

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v.data.sprite:draw{priority = p - 0.1, sceneCoords = true, frame = v.data.color}

this is assuming you intend to keep it a 1-frame thing. if each color has to be animated as well, i recommend just using separate images at that point. also, i'm pretty sure you can move the iniNPC() and rotate() calls into onTick instead of onTickEnd

[cato]

I added a line

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if v.data.sprite then...end

then right at the Draw function to avoid the error "attempt to index a sprite". It would seem to be a simpler solution to source from a particular frame instead of a particular pixel position.

Nonetheless, thank you for helping, alongside with Marioman2007 who tried with me (and failed) on Discord. Now, I am going to the same thing for another NPC, and hopefully it works when I do it myself.