[css-color-4] Slightly incorrect sRGB inverse transfer function

[jessestricker]

The sRGB inverse transfer function, the one from the non-linear to the linear sRGB values, is given in the CSS spec with a comparison that diverges from the sRGB standard.

The CSS spec states:

if (abs < 0.04045) {
  cl = c / 12.92;
}
// ...

But in the DIN EN 61966-2-1:2003-09, which is the German version of the EN 61966-2-1:2000 + A1:2003 (“sRGB standard”),
the comparison is stated using the less-than-or-equal operator, so the sample code should be:

if (abs <= 0.04045) { // note the use of the less-than-or-equal operator
  cl = c / 12.92;
}
// ...

Is this deviation from the sRGB standard intentional? Is it negligible? Or is the German version of the sRGB standard incorrect?

The affected sections are:

• Section 10.2, in the code for the transfer function
• Section 17, in function lin_sRGB(RGB)

[jessestricker]

Note: The comparison with the value 0.0031308 in the actual transfer function (from the linear to the non-linear sRGB values, as seen in function gam_sRGB(RGB) in section 17) is correct and matches the DIN EN 61966-2-1:2003-09.

[facelessuser]

It should be noted that the CSS example in Section 17 references a Wikipedia article that also uses <= as well: https://en.wikipedia.org/wiki/SRGB.

[svgeesus]

Fixed.

Note that this will only change the result if a component value is exactly 0.04045 × 255 = 10.31475