Ouch Unity 2020 Color32/Color Conversion changed values.

Unity Engine
1

I’m attempting to update a project here which is heavily math and color based. Unity changed it’s handling of Color32 / Color Conversions since our project went live. (2018LTS) And it’s the last boulder in our conversion to 2020LTS for performance improvements.

I’m wondering how folks typically handle a breaking change in a library and what work-around to utilize old functionality instead?

In my example:

Unity used to Convert float color channel to byte via (In Color32 class):
(byte)(Mathf.Clamp01(c.r) * 255)

Now it does instead (Color32 class line 46):
(byte)(Mathf.Round((Mathf.Clamp01(c.r) * 255f))),

This leads to changed color values which we cannot have for various reasons in our project. (Even though the new implementation is slightly more balanced)

So, Do I need to make a custom Color32 Class, (of old unity code) and convert references to it?
Or is there some other less sloppy way of switching back or utilizing an older library?

2

Oh wow, that’s a big juicy numeric fail! Is that really the code that Unity uses??

It’s interesting that the original one was so degenerate!!! Nothing short of 1.0f will return a 255 in the byte space. That’s a pretty big discontinuity at the top of the color channel number space.

Even the current (new) implementation is completely degenerate, with shortened spaces for 0 and 255 in the floating point space. I would think the correct data-pure way would be to:

  • multiply float by 256
  • floored it always (cast to byte/int)
  • clamped it to 0-255

To see what I mean, simulate 2550 separate floating point values between 0.0 and 1.0 in Python:

#!/usr/bin/env python3

for n in range(2560):
    i = n / 2560.0

    # degenerate method from above (note how 0 and 255 are half-sized)
    a = i * 255
    a += 0.5
    a = int(a)

    # a proper even way, data purity
    b = i * 256
    if b > 255: b = 255
    b = int(b)

    print( "%6.2ff -> %3u -> %3u" % (i, a, b))

That would have been an even transition. While the official docs do not promise (AFAIK) a particular conversion process, they certainly shouldn’t change it mid-stream.

There was a guy a few days ago noting he was getting suddenly different colors.

My advice to him and you is to avoid such a lossless conversion, even if it is a stable lossless conversion (stable when Unity doesn’t change it).

3

Kurt - yeah, I noticed the same thing, I told my partner, If they were going to screw us with a change, at least do it well! :wink: Oh well.

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