Color spaces in PsychoJL

The colorspace for your experiment is specified when you make your window. For example:

	myWin = Window( [2560, 1440], false, colorSpace = "rgba255")

Colorspaces

rgb255 red, green, and blue values from 0 to 255. Alpha (opacity) is assumed to be 255 (100%)

black = [0,0,0]
50% gray = [127, 127, 127]
white = [255, 255, 255]

rgba255 red, green, blue, and alpha values from 0 to 255.

black = [0, 0, 0, 255]
50% gray = [127, 127, 127, 255]
white = [255, 255, 255, 255]

decimal red, green, blue, and alpha values from 0.0 to 1.0. 0.0 is black and 1.0 is 100%

black = [0.0, 0.0, 0.0, 1.0]
50% gray = [0.5, 0.5, 0.5, 1.0]
white = [1.0, 1.0, 1.0, 1.0]

PsychoPy red, green, blue, and alpha values from -1.0 to 1.0. A value of 0.0 is gray, and +1.0 is 100%

black = [-1.0, -1.0, -1.0, +1.0]
50% gray = [0.0, 0.0, 0.0, +1.0]
white = [+1.0, +1.0, +1.0, +1.0]

Internally, all of these colors will be translated to rgba255 so that they work with SDL (the cross-platform graphics engine that PsychoJL uses).

Because of the color conversions, you should not access the color fields of your objects directly. Internally, the color you set is translated to an SDL color and saved in another variable, which is the variable used for drawing.

In order to translate (and update!) the color, colors should be set either when making the stimulus or using the setColor() function.
For example, while making a new Textstim:

myText = TextStim(myWin,  "Using a TextStim", [100, 100], color = [255, 255, 128])

Example using setColor()

setColor(myText, "red")

see Color setting functions

Colors in PsychoJL

Shapes and TextStim use PsychoColor as their color Type.

PsychoColor = Union{String, Vector{Int64}, Vector{Float64}}

What does that gobbledy-gook mean? It means that the constructors and functions accept strings, Vectors of Int64 (from 0-255) and Vectors of Float 64 (either -1.0...+1.0, or 0.0...+1.0) as inputs.

You can pass a string, an integer vector, or a floating point vector as a color. Keep in mind that the values you pass must be legal in the color space. For example, if you set the color space to rgba255 and try to set the color using a floating point vector, it will throw an error.

Strings (color names) are legal in all color spaces.

When the color space is rgb255 or rgba255...

String inputs will be accepted (see Colors.jl for a list of color names).

Integer Vectors with a length of 3 (RGB) or a length of 4 (RGBA) will also be accepted. If the length is 3, alpha (opacity) is assumed to be 255 (100%).

Example:

	newRect = Rect(myWin, 
			100,			# width
			100, 			# height
			[200,200],		# position
			lineColor = "dodgerblue", 			# strings are kosher
			fillColor = [255,128,128] 			# this works if the window's color space is rgb255 or rgba255
			)
	draw(newRect) 		# in PsychoPy this would have been newRect.draw()

When the color space is decimal or PsychoPy...

String inputs will be accepted (see Colors.jl for a list of color names).

Float Vectors need a length of 4 (RGBA). How they are interpreted depends on the color space.

If the color space is decimal, a value of 0.0 is considered 'black' (in that color channel), and 0.5 is considered gray (50% in that channel). On the other hand, if the color space is PsychoPy, -1.0 s considered 'black' (in that color channel), 0.0 is considered gray (50% in that channel), and +1.0 is considered white (100% in that channel).

see Colorspaces for example values.