HSL/RGB conversion


    Dec 10 2011 | 6:13 am
    I'm looking to convert between HSL and RGB, 3 floats in the range 0.,1. This is going to be inside a patcher which I am going to have multiple copies of using [poly~], so I'd like to keep it as tight as possible.
    I was a bit surprised that I couldn't find a built-in object to do this, but it seems like I have a few options:
    1. Implement using [expr] and consume via [bpatcher]. Optionally use a [swatch] to do HSL to RGB and get the saturation from RGB.
    2. Implement in Javascript in a [js] object
    3. Convert to a 1x1x3 matrix and use [jit.rgb2hsl] / [jit.hsl2rgb]
    #1 seems easiest, but I have a feeling #3 is more efficient. #2 just seems like a bad idea, if there are going to be a few dozen copies of it. (I'm still on Max 5 and the old JS for now.)
    Thoughts?

    • Dec 11 2011 | 10:23 pm
      I've been using a Jasch object, hsv2rgb to do this. Works fine for me, but I came upon your post because I was looking to see if there's a way to do it without the external. I was doing the conversion with swatch before, but it was slower - I presume because it has to update the swatch GUI interface.
    • Dec 12 2011 | 10:59 pm
      Thinking about this a bit over the last couple of days, I landed on moving this to a color manager object and taking the logic out of the poly~'ed object entirely (that one would only field (color $1 $2 $3 $4) as a property message and passes it on to its jit.gl.mesh). In the color manager I will probably use approach #3. I'll post it when it's done.
    • Nov 14 2015 | 11:06 am
      I know this thread is old - I remember seeing it back when I was looking for a solution. So for anyone searching for a list/float version of RGB to HSL and/or HSL to RGB, here are some patches I built. They may not be pretty, but they are accurate.
      The only standard objects in Max that output accurate values for HSL are the Gen objects - even if they are erroneously referred to as "hue, saturation and luminance" conversions. They are lightness, not luminance, but they are precise.
      The Jitter objects [jit.hsl2rgb] and [jit.rgb2hsl] use char data (0-255) to handle degrees (0-360).. resulting in less than precise output. iirc, the same is true for [jit.colorspace]. If you need accurate Jitter, gen or gl.gen versions, let me know.
    • Nov 14 2015 | 8:38 pm
      I've also written shaders that translate from RBG->HSL and HSL->RGB, as well as many other colorspaces. You can download them here:
    • Mar 12 2016 | 2:00 am
      @ Jesse, I am currently working on a pixel sonification project. Looking to convert RGB - HSL, may I ask.... How do you use those jxs files in max?
    • Mar 12 2016 | 2:32 am
      You can use them in a jit.gl.slab object via the @file attribute.
    • Apr 24 2016 | 5:02 pm
      hi jesse,
      this is probably a really beginner question, but i'm stumped. so, see the attached patcher below. jg.RGB2HSV.jxs seems to work fine, and now i want to iterate through each pixel, doing some examination and computation on each HSV pixel value.
      however, when i just put the output of jit.gl.slab into jit.matrix, then iterate, i seem to get a bunch of byte values. i was expecting 3 floats. so this has me worried that i'm doing something wrong. could you either explain how to properly iterate over the output of your RGB2HSV converter, or perhaps post a small patch doing just that?
      thanks. this is probably just a more general question on how to properly examine individual elements that have been converted from texture to matrix world.
      omar
    • Apr 25 2016 | 5:37 am
      The argument to jit.matrix needs to be float32, not float.
    • Apr 25 2016 | 2:46 pm
      thank you for looking! so minor, and made all the difference.
      omar
    • May 19 2017 | 4:13 am
      I would be VERY interested in having gen versions of your RGB to HSL patches!
      thanks