Colours to illustrate range

thomthom

Given a value within a given range range - say 0-100:

how would you return a colour between these colour ranges?
255, 000, 000 255, 255, 000 000, 255, 000 000, 255, 255 000, 000, 255

Top (red) would be 100
Bottom (blue) would be 0

I know I could get a result if I split the range into five segments and did a number of if-else statements. but is there a more efficient/cleaner method?

TIG

Five case/when statements with three nested case/whens seems the way ?
Unless you have a clever matrix manipulation way ?

thomthom

@tig said:

Five case/when statements with three nested case/whens seems the way ?

That's the method I know I can do.

@tig said:

Unless you have a clever matrix manipulation way ?

This is what I'm wondering is can be done.

It's out of curiosity. Wondering if there's something to learn.

Jim

Maybe Color.blend would help shorten up the code to 4 states?


blue = Sketchup;;Color.new('blue')
bluegreen = Sketchup;;Color.new(0, 255, 255)
green = Sketchup;;Color.new('green')
redgreen = Sketchup;;Color.new(255, 255, 0)
red = Sketchup;;Color.new('red')
# assuming v is (0..100)
case v
c = v / 100.0
when (0..25)
  color = blue.blend(bluegreen, c)
when (25..50)
  color = bluegreen.blend(green, c)
when (50..75)
  color = green.blend(redgreen, c)
when (75..100)
  color = redgreen.blend(red, c)

end

thomthom

` def test_clr(value = 45, max = 100, min = 0)
clr = []
clr << Sketchup::Color.new(255,0,0)
clr << Sketchup::Color.new(255,255,0)
clr << Sketchup::Color.new(0,255,0)
clr << Sketchup::Color.new(0,255,255)
clr << Sketchup::Color.new(0,0,255)

n = value / ( (max - min) / 5.0 )
index = n.to_i
ratio = n - index

c1 = clr[index-1].blend(clr[index], ratio)
def`

thomthom

hm... fails when given the max value...

thomthom

This works - with out of range recovery.


def test_clr(value = 45, max = 100, min = 0)
	clr = []
	clr << Sketchup;;Color.new(255,0,0)
	clr << Sketchup;;Color.new(255,255,0)
	clr << Sketchup;;Color.new(0,255,0)
	clr << Sketchup;;Color.new(0,255,255)
	clr << Sketchup;;Color.new(0,0,255)
	clr << Sketchup;;Color.new(0,0,255)

	value = [min, value].max
	value = [max, value].min

	n = value / ( (max - min) / 5.0 )
	index = n.to_i
	ratio = n - index

	c1 = clr[index-1].blend(clr[index], ratio)
end

But a simple switch might still be neater...

thomthom

And bugged when min is not 0. ... ok - I'm no making for an elegant solution. KISS calling?

thomthom

Ok - This one is the final deal. Easily extendible with other colour ranged by changing the array.


def value_to_color(value = 0, max = 100, min = 0)
	# Colours to translate to. First is max, last is bottom.
	# NOTE; last must appear twice!
	clr = []
	clr << Sketchup;;Color.new(255,0,0)
	clr << Sketchup;;Color.new(255,255,0)
	clr << Sketchup;;Color.new(0,255,0)
	clr << Sketchup;;Color.new(0,255,255)
	clr << Sketchup;;Color.new(0,0,255)
	clr << Sketchup;;Color.new(0,0,255)
	# Cap value to range.
	value = [min, value].max
	value = [max, value].min
	# Calculate what colours to blend between and the blending ratio.
	n = (value-min) / ( (max-min) / (clr.length-1.0) )
	index = n.to_i
	ratio = n - index
	#puts [n, index, ratio] # DEBUG
	return clr[index-1].blend(clr[index], ratio)
end

Sketchup.active_model.selection[0].material = value_to_color(30, 60, 20)

thomthom

weeeell, this is the really final deal! really!


def self.value_to_color(value = 0, max = 100, min = 0)
	# Colours to translate to. First is max, last is bottom.
	clr = []
	clr << Sketchup;;Color.new(255,0,0)
	clr << Sketchup;;Color.new(255,255,0)
	clr << Sketchup;;Color.new(0,255,0)
	clr << Sketchup;;Color.new(0,255,255)
	clr << Sketchup;;Color.new(0,0,255)
	# Cap value to range.
	value = [min, value].max
	value = [max, value].min
	# Calculate what colours to blend between and the blending ratio.
	n = (value-min) / ( (max-min) / (clr.length-1.0) )
	index1 = n.to_i
	index2 = [index1+1, clr.length-1].min
	ratio = n - index1
	#puts [value, n, index, ratio].inspect # DEBUG
	return clr[index2].blend(clr[index1], ratio)
end

I had confused how the blend weighting worked. Fixed. +some cleaning up.

Chris Fullmer

Very cool Thom, thanks for posting this. Its something that has crossed my mind recently. I'll be sure to look through your code,

Chris

Chris Fullmer

I've got this snippet in a top secret little project I'm working (ok, well its top secret but I've shared it with quite a few other people, so its not that top secret). Anyhow, the code works great Thom, but I only just recently realized it does not cover the entire range of colors. To get it to come full swing back to red, one woul need to add the lines:

clr << Sketchup::Color.new(255,0,255) clr << Sketchup::Color.new(255,0,0)

to the end of the other similar lines so that it adds the magenta color to the array and finally back to red. Then you have a true full spectrum represented in this lovely gradient.

Thanks again Thom!

Chris

thomthom