# # File: # color3.py # # Synopsis: # Draws HSV color wedges and tests color conversion functions. # # Category: # Colors # # Author: # Fred Clare # # Date of initial publication: # December, 2005 # # Description: # Create color wheels in HSV (hue, saturation, value) space. # Each wheel is produced with a different value of V (the value # parameter in HSV space). Each wheel is composed of 16 wedges. # The value for the hue remains the same within each wedge, and # the value for the saturation varies linearly from the center # (saturation = 0.) to the outer rim (saturation = 1.) within each # wedge. The hues vary from 0. to 360. counterclockwise around # the color wheel starting at pure red (hue = 0.) and returning # to pure red. # # Also, this example contains basic tests for the six color # conversion functions: # Ngl.hsvrgb - (Hue, Saturation, Value) to (Red, Green, Blue) # Ngl.rgbhsv - (Red, Green, Blue) to (Hue, Saturation, Value) # Ngl.hlsrgb - (Hue, Lightness, Saturation) to (Red, Green, Blue) # Ngl.rgbhls - (Red, Green, Blue) to (Hue, Lightness, Saturation) # Ngl.yiqrgb - (luminance, chromaticity) to (Red, Green, Blue) # Ngl.rgbyiq - (Red, Green, Blue) to (luminance, chromaticity) # # Effects illustrated: # o Colors drawn in HSV space. # o Converting from HSV space to RGB space. # o Drawing lines and polygons in NDC space. # o Conversions between the three color spaces: RGB, HSV, YIQ. # # Output: # o Three color wheels are drawn using three different settings # for the "value" component in HSV space. # o Possible warnings to standard out if color conversion tests fail. # from __future__ import print_function import Ngl import math import numpy # # Define the hues, and saturations, and values (the HSV) to be used. # hues = Ngl.fspan(0., 337.5, 16) saturations = Ngl.fspan(0., 1., 4) values = [0.50, 0.75, 1.00] # # Define the radian increment to be used for spacing the # color wedges around the wheels. # pi = 3.14159265 radian_inc = 2*pi/float(len(hues)) # # Specify the Y-coordinates for the saturation labels. # slab_y = [.375, .292, .217] # # Define Resource objects for the polygons and text. # poly_res = Ngl.Resources() text_res = Ngl.Resources() # # Set up arrays to hold the polygon coordinates. # x = numpy.zeros(4,'f') y = numpy.zeros(4,'f') # # Open a workstation with a black background and a white # foreground. Specify a small color map so that there is # enough room to add the 192 colors for all three color wheels. # rlist = Ngl.Resources() rlist.wkForegroundColor = "White" rlist.wkBackgroundColor = "Black" rlist.wkColorMap = "cyclic" wks_type = "png" wks = Ngl.open_wks(wks_type,"color3",rlist) # # Loop on the values, drawing a picture for each value. # for value in values: # # Loop on the hues. # for hue in hues: angle1 = (hue*len(hues)/360. - 0.5) * radian_inc angle2 = (hue*len(hues)/360. + 0.5) * radian_inc x[0] = x[3] = y[0] = y[3] = 0.0 # # Loop on the saturations. # sindex = 0 for saturation in saturations: r,g,b = Ngl.hsvrgb(hue,saturation,value) poly_res.gsFillColor = [r,g,b] # Ngl.new_color(wks,r,g,b) rlen = 0.25*(3.*saturation + 1.) x[1] = math.cos(angle1) * rlen y[1] = math.sin(angle1) * rlen x[2] = math.cos(angle2) * rlen y[2] = math.sin(angle2) * rlen xc = 0.1 + (x + 1.2)/3. # Conceptual user space is [-1.2, 1.2] in yc = 0.1 + (y + 1.2)/3. # X and Y -- map to [0.1, 0.9] NDC space. Ngl.polygon_ndc(wks,xc,yc,poly_res) x[0] = x[1] x[3] = x[2] y[0] = y[1] y[3] = y[2] # # Label the saturation levels (the zero saturation # level at the center of the wheel is not labeled). # if (saturation != 0.): text_res.txFontHeightF = 0.022 text_res.txJust = "CenterCenter" slabel = "S = {:4.2f}".format(saturation) Ngl.text_ndc(wks, slabel, 0.5, slab_y[sindex],text_res) sindex = sindex+1 # # Add a main title specifying the "value". # text_res.txFontHeightF = 0.03 text_res.txJust = "CenterCenter" Ngl.text_ndc(wks, "Value = {:4.2f}".format(value), 0.5, 0.9, text_res) # # Mark the hues. # text_res.txFontHeightF = 0.025 text_res.txJust = "CenterLeft" Ngl.text_ndc(wks, "Hue = 0.", 0.86, 0.5, text_res) Ngl.polyline_ndc(wks, [0.827, 0.843], [0.5, 0.5]) Ngl.text_ndc(wks, "Hue = 45.", 0.767, 0.747, text_res) Ngl.polyline_ndc(wks, [0.730, 0.750], [0.730, 0.747]) Ngl.text_ndc(wks, "Hue = 315.", 0.767, 0.253, text_res) Ngl.polyline_ndc(wks, [0.733, 0.752], [0.267, 0.251]) text_res.txJust = "CenterRight" Ngl.text_ndc(wks, "Hue = 135.", 0.233, 0.746, text_res) Ngl.polyline_ndc(wks, [0.270, 0.250], [0.731, 0.747]) Ngl.text_ndc(wks, "Hue = 225.", 0.233, 0.254, text_res) Ngl.polyline_ndc(wks, [0.270, 0.250], [0.270, 0.253]) # # End picture. # Ngl.frame(wks) # # Illustrations and tests for the color conversion functions. # # # Set a tolerance limit for HLS and HSV tests. # eps = 0.00001 # # HLS to RGB: (120., 50., 100.) -> (1., 0., 0.) # r,g,b = Ngl.hlsrgb(120., 50., 100.) if numpy.sometrue(numpy.greater(numpy.fabs([r-1., g, b]), eps)): print("color3: hlsrgb test failed") # # RGB to HLS: (1., 0., 0.) -> (120., 50., 100.) # h,l,s = Ngl.rgbhls(1., 0., 0.) if numpy.sometrue(numpy.greater(numpy.fabs([h-120.,l-50.,s-100.]), eps)): print("color3: rgbhls test failed") # # HSV to RGB: (120., 1., 1.) -> (0., 1., 0.) # r,g,b = Ngl.hsvrgb(120., 1., 1.) if numpy.sometrue(numpy.greater(numpy.fabs([r, g-1., b]), eps)): print("color3: hsvrgb test failed") # # RGB to HSV: (0., 1., 0.) -> (120., 1., 1.) # h,s,v = Ngl.rgbhsv(0., 1., 0.) if numpy.sometrue(numpy.greater(numpy.fabs([h-120., s-1., v-1.]), eps)): print("color3: hsvrgb test failed") # # Set a tolerance limit for the YIQ tests. # eps = 0.01 # # YIQ to RGB: (0.58701, -0.27431, -0.52299) -> (0., 1., 0.) # r,g,b = Ngl.yiqrgb(0.58701, -0.27431, -0.52299) if numpy.sometrue(numpy.greater(numpy.fabs([r, g-1., b]), eps)): print("color3: yiqrgb test failed") # # RGB to YIQ: (1., 1., 1.) -> (1., 0., 0.) # y,i,q = Ngl.rgbyiq(1., 1., 1.) if numpy.sometrue(numpy.greater(numpy.fabs([y-1., i, q]), eps)): print("color3: rgbyiq test failed") Ngl.end()