python - Range values to pseudocolor -

i have array of floats (in python) might range 0 100. want create pseudo-color image colors vary green (corresponding 0) red (100). similar pcolor matplotlib. however, not want use pcolor.

is there function pseudocolorforvalue(val,(minval,maxval)) returns rgb triple corresponding pseudo-color value 'val'? also, there flexibility in function choose whether display colors green-to-red or red-to-green?

thanks, nik

you write own function converted values 0...100 => 0...120 degrees , used value h (or angle) of color in hsv (or hls) colorspace. converted rgb color display purposes. linearly interpreted color better when they're calculated in colorspace: here's hsv colorspace looks like:

update:

good news, pleasantly surprised discover python has colorspace conversion routines in built-in colorsys module (they mean "batteries included"). what's nice makes creating function described easy, illustrated below:

from colorsys import hsv_to_rgb  def pseudocolor(val, minval, maxval):     """ convert val in range minval..maxval range 0..120 degrees         correspond colors red , green in hsv colorspace.     """     h = (float(val-minval) / (maxval-minval)) * 120      # convert hsv color (h,1,1) rgb equivalent.     # note: hsv_to_rgb() function expects h in range 0..1 not 0..360     r, g, b = hsv_to_rgb(h/360, 1., 1.)     return r, g, b  if __name__ == '__main__':     steps = 10      print('val       r      g      b')     val in range(0, 100+steps, steps):         print('{:3d} -> ({:.3f}, {:.3f}, {:.3f})'.format(                                                 val, *pseudocolor(val, 0, 100))) 

output:

val       r      g      b   0 -> (1.000, 0.000, 0.000)  10 -> (1.000, 0.200, 0.000)  20 -> (1.000, 0.400, 0.000)  30 -> (1.000, 0.600, 0.000)  40 -> (1.000, 0.800, 0.000)  50 -> (1.000, 1.000, 0.000)  60 -> (0.800, 1.000, 0.000)  70 -> (0.600, 1.000, 0.000)  80 -> (0.400, 1.000, 0.000)  90 -> (0.200, 1.000, 0.000) 100 -> (0.000, 1.000, 0.000) 

here's sample showing output looks like:

i think may find colors generated nicer in other answer.

generalizing:

it's possible modify function little more generic in sense work colors other red , green hardcoded it.

here's how that:

def pseudocolor(val, minval, maxval, start_hue, stop_hue):     """ convert val in range minval..maxval range start_hue..stop_hue         degrees in hsv colorspace.     """     h = (float(val-minval) / (maxval-minval)) * (stop_hue-start_hue) + start_hue      # convert hsv color (h,1,1) rgb equivalent.     # note: hsv_to_rgb() function expects h in range 0..1 not 0..360     r, g, b = hsv_to_rgb(h/360, 1., 1.)     return r, g, b  if __name__ == '__main__':     # angles of common colors in hsv colorspace     red, yellow, green, cyan, blue, magenta = range(0, 360, 60)     steps = 10      print('val       r      g      b')     val in range(0, 100+steps, steps):         print('{:3d} -> ({:.3f}, {:.3f}, {:.3f})'.format(                 val, *pseudocolor(val, 0, 100, yellow, blue))) 

results: