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Change opacity without a round trip through HLC - #16
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change(.opacity, …) converted the color to HLC and back just to set the opacity, which shifted the RGB components by up to about 1e-6 (e.g. green 0 became 1.7e-6). Opacity is the same in every color space, so it now goes through the RGB path. The never reached .opacity branches of the HSB and HLC helpers are removed.
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Overview
Color.change(.opacity, to:)andchange(.opacity, by:)converted the color to HLC and back just to set the opacity. That round trip shifted the RGB components by up to about 1.7e-6 (pure green got a red component of 1.7e-6). Opacity is the same in every color space, so it now goes through the RGB path. The.opacitycases of the HSB and HLC helpers were never reached and are removed.This is a precision fix: the drift is far below what a display shows, but it makes
change(.opacity, …)keep the RGB values exactly as they were.Split out of #7.
How this was verified
ColorExtTests.changingOpacityKeepsTheRGBComponentschecks three colors with a tolerance of 5e-7 (the float precision of the platform colors is around 1e-7).Red, with
main'sColorExt.swift:Green, this branch: