Talk:HSL and HSV

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please explain

The article says both The HSL color space was invented in 1938 by Georges Valensi and computer graphics pioneers at PARC and NYIT developed the HSV model in the mid-1970s, formally described by Alvy Ray Smith[10] in the August 1978 issue of Computer Graphics.

What does this mean? Is this contradictory, or if not, why? CapnZapp (talk) 06:56, 16 June 2018 (UTC)[reply]

Judging only by your quotes, there doesn't seem to be a problem, since HSL and HSV are different things. ➧datumizer ☎ 04:06, 27 August 2018 (UTC)[reply]

per CapnZapp and datumizer thoughts I elaborated on HSL "invented for television" and HSV "introduced the HSV model for computer display technology" in an attempt to clarify the original concern without altering meaning. HSL_and_HSV&diff=prev&oldid=901938209 Rdela (talk) 10:12, 15 June 2019 (UTC)[reply]

I know this topic is many years old, but the opening paragraph is misleading and confusing, partly due to bad grammar and partly due to the contradications that @CapnZapp points out.

The body of the article reads:

"The HSL color space was invented for television in 1938 by Georges Valensi..."

and later:

"...computer graphics pioneers at PARC and NYIT developed the HSV model in the mid-1970s..."

But the leading sentence of the article says that both HSL and HSV were designed in the 1970s, which is misleading at best. It also seems to use an appositive incorrectly: "...are alternative representations of the RGB color model, designed in the 1970s... to more closely align with the way human vision perceives color..." This implies that it is RGB that was designed in the 1970s and that RGB was designed to align with how humans perceive color. I believe it's incorrect to say that HSL and HSV are "representations" of RGB. HSL, HSV, and RGB are each color models or gamuts in their own right. They are all alternatives to one another.

I recommend that the reference to RGB and the misleading fact that both HSL and HSV were invented in the 1970s be removed completely from the leading paragraph. That level of detail is appropriate for the body of the article where it can be treated more carefully. 2600:1700:2820:5630:3DE7:6C28:D3AA:FC12 (talk) 20:03, 13 June 2023 (UTC)[reply]

I don't have the expertise to totally fix it but will take out some of the unsourced stuff that looks wrong. North8000 (talk) 20:50, 13 June 2023 (UTC)[reply]

I wrote this article to be clear and well sourced over a decade ago, but in the mean time it has suffered from gradual deterioration. The stuff about TV color broadcasting is not really directly relevant IMO, and is not sourced to secondary sources. It would be nice if someone who is an expert on old television broadcast standards could write a clear summary, but this article isn't really the place for it IMO. –jacobolus (t) 09:53, 10 January 2024 (UTC)[reply]

Color space where full saturation ignores intensity/lightness/luma/luminosity/value

Is there a color space similar to HSL/HSV/HSI such that 0% saturation ignores hue and 100% saturation ignores intensity/lightness/luma/luminosity/value? Notice the bottom of the example: solid yellow.

— Preceding unsigned comment added by Sollyucko (talk • contribs) 02:54, 5 February 2019 (UTC)[reply]

Color conversion formulae: HSL to RGB

There is a discrepancy in the formula for $(R_{1},G_{1},B_{1})$ .

${H\in [0^{\circ },360^{\circ }]}$ . H is cyclic, so the same results should occur for H=0 and H=360.
$H^{\prime }={\frac {H}{60^{\circ }}}$ , but H'=0 when H=0 and H'=6 when H=360. The six cases for $(R_{1},G_{1},B_{1})$ cover ⌈H'⌉ from 1 to 6, but H'=0 yields (0,0,0), but H'=6 is (C,0,X). When H'=0, you should get the same result when H'=6. — Preceding unsigned comment added by Chelmite (talk • contribs) 20:28, 8 June 2020 (UTC)[reply]

I have changed the piecewise function back to the previous version, at some point someone changed it from inequalities to a ceiling function, but it was not correct as written because ceil(0) != 1 --Alextgordon (talk) 13:46, 16 July 2020 (UTC)[reply]

Issues with HSI to RGB formulas

Unless I am missing something, I believe there are issues with the HSI to RGB formulas. The result of the formula C = (3 · I · S) / (1 + Z) can yield values where 0 ≤ C ≤ 3. Values where C + m > 1 are problematic, since this will result in values for R, G, and B that are outside the acceptable range of 0 to 1 (inclusive). Techfan101 (talk) 16:17, 1 March 2021 (UTC)[reply]

"HSV, V for light" -- ?

It says that HSV represent { "how the object appear under light" / amount of reflected light, by the V value } . This is not true .?

HSV's V behave irrelevantly to light, for some colors . If you use any white light source, you get what HSL's L does . Try to use these 2 values on #49301D . In HSV, after 50% HSL's L, the color still can be made brighter, but in reality, under white light, surface with such color will only reflect more and more white, as in HSL .

For preview,

HSV -- https://www.getpaint.net/download.html ,
HSL -- https://www.w3schools.com/colors/colors_hsl.asp .

Irvnriir (talk) 16:52, 11 March 2021 (UTC)[reply]

I reverted to an older version of the lead section. That was nonsense. –jacobolus (t) 08:29, 10 January 2024 (UTC)[reply]

Formula section poorly written

I'm not a wikipedian, I'm not sure how one would request a rewrite, but the section describing the various conversion formulae has grammatical mistakes and is just in general really hard to read.

--71.231.105.84 (talk) 11:04, 15 April 2022 (UTC)[reply]

It was clear and carefully written a decade ago. unfortunately entropy is generally not kind to wikipedia articles. –jacobolus (t) 08:29, 10 January 2024 (UTC)[reply]

Section 3.6 Examples

Is it just me, or are some of the examples wrong? Or maybe they're using some idealized values?

For example, #008000 would have the RGB values of (0,128,0). If you normalize these values, you should get (0.0,0.501,0.0), but in the example it gives much "nicer looking" values of (0.0,0.500,0.0). This affects the downstream calculation as well. So instead of getting HSV of (120.0,1.00,0.502), you get (120.0,1.00,0.500). Certainly a "nicer looking" result, but unless I'm missing something, it's slightly inaccurate.

A couple online calculators seem to give the results I'm expecting (different from the examples on this page). So, what am I missing here?

Justin T Conroy (talk) 05:52, 26 March 2024 (UTC)[reply]

The exact (R, G, B) values are canonical here, and the 8-bit/channel version is an approximation (which is why it is only an intentionally invisible hexadecimal string, rather than a numerical column). The approximation is necessary because HTML/CSS (and many operating systems and displays) are only capable of describing colors using 8 bit/channel. If you instead treated the 8 bit/channel colors as canonical and computed a decimal approximation for the (R, G, B) columns, that would be worse, because 255ths are not cleanly expressible as decimal numbers, so it would not be obvious which values should be taken as canonical for putting into the definitional formulas for these various color representations between a fraction out of 255 vs. a fraction out of 1000 (3 decimal places). The point of the examples is substantially so people can double-check implementations of these formulas, so the resulting confusion would compromise that goal. –jacobolus (t) 07:40, 26 March 2024 (UTC)[reply]

So, how would you go about converting the hexadecimal values to these canonical RGB values? Justin T Conroy (talk) 15:05, 26 March 2024 (UTC)[reply]

The conversion went the other way. If you start with an arbitrary number between 0 and 1, you can multiply it by 255 and then round to the nearest integer, which will be between 0 and 255 or in hexadecimal between 0x00 and 0xFF. For example,

0.750\times 255=191.25\approx 191=11\cdot 16+15\cdot 1.

So the number 0.750 corresponds (approximately) to 0xBF. If instead you treated 191/255 as the canonical value, then the decimal fraction for that is 0.749... –jacobolus (t) 16:37, 26 March 2024 (UTC)[reply]