Pixel color gradient

rrraptor · July 2020

Just wonder, is that suppose to work like that or not.

If Pixel object is fully transparent then you wont see a gradient.

local pixel = Pixel.new(0, 0, 500, 500)
pixel:setColor(0xFF0000, 1, 0x0D8CFF, 1, 0xFF0000, 1, 0x0D8CFF, 1) -- nothing to see
stage:addChild(pixel)

But if its not transparent then everything ok.

local pixel = Pixel.new(0, 0, 500, 500)
pixel:setColor(0xffffff, 1) -- set color to white
pixel:setColor(0xFF0000, 1, 0x0D8CFF, 1, 0xFF0000, 1, 0x0D8CFF, 1) -- use same function to create gradient but now it works
stage:addChild(pixel)

hgy29 · July 2020

Yes, the gradient (per vertex) color is in fact multiplied by the constant color.

MoKaLux · July 2020

rrraptor said:
If Pixel object is fully transparent then you wont see a gradient.

I suppose that's normal, like every sprite objects

opacity = 0 you don't see it, > 0 you see it

rrraptor · July 2020

I experimented with the layout system and gradients and got this

Source:
https://github.com/MultiPain/Gideros_examples/blob/master/ColorPicker/

keszegh · July 2020

@rrraptor thanks for sharing, i just planned to add similar color picker to my app, so this will be good for this, probably i will need to modify it only minimally for my purposes.

keszegh · July 2020

@rrraptor

ColorPicker.lua:212: attempt to perform arithmetic on field 'cellSpacingX' (a nil value)
stack traceback:
ColorPicker.lua:212: in function 'init'
[string "property.lua"]:59: in function '__new'
[string "property.lua"]:66: in function 'new'
main.lua:3: in main chunk

rrraptor · July 2020

@keszegh are you using latest version of gideros?

https://wiki.giderosmobile.com/index.php/Sprite:setLayoutParameters

cellSpacingX: horizontal margin between cells. since 2020.7
cellSpacingY: vertical margin between cells. since 2020.7

rrraptor · July 2020

Anyways, its just minimum size calulations. You can safely remove "layoutParams.cellSpacingX * (info.width - 1)" and "layoutParams.cellSpacingY * (info.height - 1)" since its not implemented in older versions.

rrraptor · July 2020

This should work fine in older version. Ive added a local variable at line 100 to achieve similar effect.

keszegh · July 2020

thanks, i indeed had an older version, i did not even notice.

rrraptor · July 2020

@hgy29 I got this when shader is applied to a Pixel object (with OR without gradient, does not matter). What is that?

Code here:
https://github.com/MultiPain/Gideros_examples/tree/master/GammaCorrection
But I replaced a few lines:

for i,c in ipairs(COLORS) do
	-- gamma correct gradient with shader
	local grad1 = Pixel.new(0xffffff, 1, GW, H - 25)
	grad1:setColor(c[1], 1, c[2], 1, 90)
	grad1:setShader(shader)
	gr:add(grad1)
 
	-- regular gradient
	local grad2 = Pixel.new(0xffffff, 1, GW, H - 25)
	grad2:setColor(c[1], 1, c[2], 1, 90)
	gr:add(grad2)
end

hgy29 · July 2020

Looks like your shader expect a texture, while Pixel with plain or gradient color doesn't use any! I guess the shader is sampling from the last used texture, which must be the font texture.

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