What does ImageData:getPixel return exactly? (new questions)

[Buddy4point0]

Your function is trying to get a pixel outside of the image. This throws an exception and love quits.
ImageData in love goes from 0, 0 to width-1, height-1. To stay inside the image you could change

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imageData:getPixel(w,h)

to

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imageData:getPixel(w-1,h-1)

Thank you very much! I had no idea that imagedata was read like that.

Here's the final working version my function in case it helps anyone else.

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function readImg(fileName)
	local iD = love.image.newImageData(fileName)
	local t = {img = love.graphics.newImage(fileName),map = {}}
	local width = t.img:getWidth()
	local height = t.img:getHeight()
	local temp

	for w = 1,width,-1 do
		t.map[w] = {}

		for h = 1,height,-1 do
			temp = {iD:getPixel(w,h)}

			if temp[4] > 0 then
				t.map[w][h] = true
			else
				t.map[w][h] = false
			end
		end
	end

	return t
end

[Robin]

I read it, and I don't agree with you or the creator of the article at all.
To be more specific, I have to make a pixel perfect collision system for what I'm working on right now. So I figure I might as well make it re-useable.

But that's exactly what the writer of the article was saying: you don't create a collision system out of the blue, but you make it with a specific use (i.e. your game) in mind. Making it reusable is the second step, not the first.

Ok, I looked on the Lua 5.1 Reference Manualand I don't see anything about lists.
What are they and how would I use the information in it? If you don't feel like answering though, it's fine because I got it figured out thanks to Thelinx.

Lists are very weak in Lua, they disappear in a puff of smoke, for example:

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function afunc(...)
    print(...) -- ... is a list here. You can pass it to another function.
    print((...)) -- only the first element in the list is passed
    -- lists can be put into tables like this:
    atable = {...} 
    return 1, 2, 3 -- this function returns a list
end

Some explanation: http://www.lua.org/pil/5.1.html and http://www.lua.org/pil/5.2.html

[Buddy4point0]

Ok, I looked on the Lua 5.1 Reference Manualand I don't see anything about lists.
What are they and how would I use the information in it? If you don't feel like answering though, it's fine because I got it figured out thanks to Thelinx.

Lists are very weak in Lua, they disappear in a puff of smoke, for example:

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function afunc(...)
    print(...) -- ... is a list here. You can pass it to another function.
    print((...)) -- only the first element in the list is passed
    -- lists can be put into tables like this:
    atable = {...} 
    return 1, 2, 3 -- this function returns a list
end

Some explanation: http://www.lua.org/pil/5.1.html and http://www.lua.org/pil/5.2.html

I'll read up on this and get back to you.

[Boolsheet]

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for w = 1, width, -1 do

Are you sure this is what you want?
It will never enter the loop unless width is 1 or lower.

[Robin]

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for w = 1, width, -1 do

Are you sure this is what you want?

I think it was

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for w = 1, width do

before.

Buddy4point0: I think you should change it to this:

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for w = 0, width-1 do

[Buddy4point0]

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for w = 1, width, -1 do

Are you sure this is what you want?

I think it was

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for w = 1, width do

before.

Buddy4point0: I think you should change it to this:

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for w = 0, width-1 do

So when reading images, say a 64x64 image, I would have to read pixels 0-63 across and 0-63 down?

[Robin]

So when reading images, say a 64x64 image, I would have to read pixels 0-63 across and 0-63 down?

Yeah, I think so.