getPixel in a line

[szmol96]

Hi guys.
I have bumped into a problem while making my own collision system. I know how to check for non-transparent pixels, but i have no idea how to check if there are any in a horizontal line. I have tried a for loop, but my character falls through the ground. Here is the function code:

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function maskedHLine(x, y, length, image)
	for i = 1, length do
		local r, g, b, a = imageData:getPixel( x + i, y )
		if not a == 0 then
			return true
		end
	end
	return false
end

and here is the code for falling:

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if maskedHLine(player.x -16, player.y + 16, 32, "img/map.png") == false then
		player.ySpeed = 200
		player.onGround = false
	else
		player.ySpeed = 0
		player.onGround = true
	end

Could someone help me out?

[Robin]

Your boolean expressions are weird. The problem's here

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if not a == 0 then

which means the same as:

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if (not a) == 0 then

which will always be false if a is a number.
Use this:

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if a ~= 0 then

or

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if a > 0 then

The other one is bad too, but it's merely confusing, not wrong: x == false is better written as not x.

EDIT: also, maskedHLine isn't a very good name, consider renaming it to something like collidesWIthLine or something. It took me a while to figure out when it was supposed to return true. Also, pixel collision is s-l-o-w, know what you're getting yourself into.

[szmol96]

It worked, thank you very much.