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    RenderTarget probable issue

    tetnictetnic Member
    edited July 2019 in General questions
    Hi all,

    I'm trying to read the color values of a PNG, to do that I do the following:

    - Load the image into a Bitmap
    - Draw the bitmap inside a RenderTarget
    - Then I read color values pixel by pixel

    The problem is that RenderTarget seems to return wrong values for some pixels. Consider the following image



    When calling RenderTarget:getPixel() on fully transparent pixels it returns the correct values for them (color = 0x000000, alpha = 0), but for other pixels that are "black" it returns again the previous values (color = 0x000000, alpha = 0).

    Due to this fact I'm unable to distinguish between fully transparent pixels and opaque black ones.

    Anyone have encountered the same issue and knows how to overcome this obstacle?

    Thank you.
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    Comments

    • tetnictetnic Member
      Reading the sourcecode I also tried several values of "format" when loading the Texture, but nothing changed.
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    • hgy29hgy29 Maintainer
      Take a look at PixelsClown example, it does what you are trying to do and it seems to work
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    • tetnictetnic Member
      Ok, it is was due to a my fault when indexing the pixels inside a table.

      Thank you for your help.

      Likes: MoKaLux

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    • MoKaLuxMoKaLux Member
      edited July 2019
      hello @tetnic as an exercise I tried to answer your question. I came up with this piece of code.

      Maybe that can help?
      local source = Bitmap.new(Texture.new("gfx/enemy01.png", true))
local rt = RenderTarget.new(source:getWidth(), source:getHeight())
local bmp = Bitmap.new(rt)
bmp:setPosition(200, 0)
stage:addChild(bmp)
rt:draw(source)
 
local pixels = {}
local points = {}
 
local t = 1
for i = 1, bmp:getWidth() do
	for j = 1, bmp:getHeight() do
		local xcolor, xalpha = rt:getPixel(i, j)
		table.insert(pixels, t, {color=xcolor, alpha=xalpha})
		t += 1
	end
end
for i = 1, #pixels do
	local pixel = Pixel.new(pixels[i].color, pixels[i].alpha, 1, 1)
	table.insert(points, #points + 1, pixel)
end
 
t = 1
for i = 1, bmp:getWidth() do
	for j = 1, bmp:getHeight() do
		local point = points[t]
		point:setPosition(i, j)
		stage:addChild(point)
		t += 1
	end
end

      PS: I don't know if it is clean code. Does it even answer your original question? I think I got lost here!

      Likes: antix

      my growING GIDEROS github repositories: https://github.com/mokalux?tab=repositories
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    • tetnictetnic Member
      Hi @MoKaLux,

      Yes the code is clear and in general it is the same thing I do. Thank you for your help :smile:

      Mauro

      Likes: MoKaLux

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    • MoKaLuxMoKaLux Member
      edited July 2019
      gideros is so much fun and I need to practice more so I went with some more: scaling.
      local source = Bitmap.new(Texture.new("gfx/enemy01.png", true))
local rt = RenderTarget.new(source:getWidth(), source:getHeight())
local bmp = Bitmap.new(rt)
bmp:setPosition(200, 0)
stage:addChild(bmp)
rt:draw(source)
 
local pixels = {}
local points = {}
 
local scale = 10
 
local t = 1
for i = 1, bmp:getWidth() do
	for j = 1, bmp:getHeight() do
		local xcolor, xalpha = rt:getPixel(i, j)
		table.insert(pixels, t, {color=xcolor, alpha=xalpha})
		t += 1
	end
end
for i = 1, #pixels do
	local pixel = Pixel.new(pixels[i].color, pixels[i].alpha, scale, scale)
	table.insert(points, #points + 1, pixel)
end
 
t = 1
for i = 1, bmp:getWidth() do
	for j = 1, bmp:getHeight() do
		local point = points[t]
		point:setPosition(((i - 1) * scale) + 100, ((j - 1) * scale) + 100)
		stage:addChild(point)
		t += 1
	end
end

      image.png
      482 x 852 - 18K

      Likes: antix

      my growING GIDEROS github repositories: https://github.com/mokalux?tab=repositories
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