René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Perceptually uniform cyclic colormaps","articleBody":"We are considering packing proplot with some custom *cyclic colormaps*. Below is an example that I'm toying with.\r\n\r\n@bradyrx It turns out that luminance + chroma as sine curves in quadrature give you uniform, colorblind-friendly *single hue* maps! I tried making a *cyclic multihue* map this way but it turns out to be way harder. HSL and HPL give weird zig-zags in chroma/luminance and in HCL, it's almost impossible to \"thread the needle\" between valid values (i.e. values that translate to non-impossible RGB colors).\r\n\r\nFeel free to play with this example:\r\n\r\n```python\r\nimport proplot as plot\r\nimport numpy as np\r\nspace = 'hcl'\r\nhue = 'medium blue'\r\nreverse = False\r\nluminance_shift = 0\r\nsaturation_shift = np.pi/2\r\nluminance_offset = 0\r\nsaturation_offset = 0\r\nluminance_scale = 80\r\nsaturation_scale = 60\r\nluminance = lambda x: luminance_offset + 50 + luminance_scale*np.sin(x*2*np.pi + luminance_shift)/2\r\nsaturation = lambda x: saturation_offset + 50 + saturation_scale*np.sin(x*2*np.pi + saturation_shift)/2\r\ncmap = plot.PerceptuallyUniformColormap.from_hsl('_cyclic',\r\n    # hue=(hue, hue + 360)[::1 - 2*reverse], # cyclic hues!\r\n    hue=hue, # constant hue!\r\n    saturation=saturation, luminance=luminance,\r\n    cyclic=True, space=space)\r\ncmap = cmap.shifted(180) # optionally shift\r\nf = plot.show_channels(cmap, rgb=False, axwidth=1.5)\r\nf, ax = plot.subplots()\r\nax.pcolormesh(np.ones((30,30)).cumsum(axis=0) % 10, cmap=cmap, colorbar='b')\r\nax.format(suptitle='Cyclic colormap test')\r\n```\r\n\r\n![image](https://user-images.githubusercontent.com/19657652/69698344-52e97780-10a2-11ea-8760-181e54457938.png)\r\n\r\n![image](https://user-images.githubusercontent.com/19657652/69698350-57ae2b80-10a2-11ea-978d-abfe45f45310.png)\r\n","author":{"url":"https://github.com/lukelbd","@type":"Person","name":"lukelbd"},"datePublished":"2019-11-27T06:02:43.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/70/proplot/issues/70"}