Composite translucent colors
Resolve foreground alpha against a backdrop before measuring or storing the visible color.
Backdrop
opaque
#2563eb
Foreground
alpha 0.65
#f43f5ea6
Visible result
opaque
#ac4c8f
Resolve the layer stack into one visible color
The translucent rose foreground over the opaque blue backdrop becomes #ac4c8f with alpha 1.
Composite before evaluating the result
ContrastSolver::composite() accepts the foreground first and the background second, then returns an sRGB color.
<?php
use PhpColor\Color\Color;
use PhpColor\Color\Contrast\ContrastSolver;
$foreground = Color::parse('rgb(244 63 94 / 65%)');
$backdrop = Color::parse('#2563eb');
$visible = ContrastSolver::composite($foreground, $backdrop);
echo $visible->toHex(true);
// #ac4c8fffCompositing depends on the backdrop
A translucent color has no single visible RGB result until the background and layer order are known.
OrderThe first argument is foreground; the second is background.
SpaceThe returned object is an sRGB color.
Opaque backdropAn opaque background makes this demonstrated result opaque.
ContrastMeasure contrast against the composited representation viewers receive.