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ICC: Implement TRC inversion in from_pcs for parametric curves
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3 changed files with 71 additions and 8 deletions
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@ -1551,6 +1551,7 @@ ErrorOr<void> Profile::from_pcs(FloatVector3 const& pcs, Bytes color) const
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// greenTRC^-1, and blueTRC^-1 function is undefined. If a one-dimensional curve is constant, the curve cannot be
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// inverted."
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// Convert from XYZ to linear rgb.
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// FIXME: Inverting matrix and curve on every call to this function is very inefficient.
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auto const& red_matrix_column = this->red_matrix_column();
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auto const& green_matrix_column = this->green_matrix_column();
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@ -1561,13 +1562,22 @@ ErrorOr<void> Profile::from_pcs(FloatVector3 const& pcs, Bytes color) const
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red_matrix_column.Y, green_matrix_column.Y, blue_matrix_column.Y,
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red_matrix_column.Z, green_matrix_column.Z, blue_matrix_column.Z
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};
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if (!forward_matrix.is_invertible())
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return Error::from_string_literal("ICC::Profile::from_pcs: matrix not invertible");
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auto matrix = forward_matrix.inverse();
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FloatVector3 linear_rgb = matrix * pcs;
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auto evaluate_curve_inverse = [this](TagSignature curve_tag, float f) {
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auto const& trc = *m_tag_table.get(curve_tag).value();
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VERIFY(trc.type() == CurveTagData::Type || trc.type() == ParametricCurveTagData::Type);
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if (trc.type() == CurveTagData::Type) {
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TODO();
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return 0.f;
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}
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return static_cast<ParametricCurveTagData const&>(trc).evaluate_inverse(f);
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};
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// Convert from linear rgb to device rgb.
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// See equations (F.8) - (F.16) above.
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// FIXME: The spec says to do this, but it loses information. Color.js returns unclamped
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// values instead (...but how do those make it through the TRC?) and has a separate
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@ -1576,12 +1586,13 @@ ErrorOr<void> Profile::from_pcs(FloatVector3 const& pcs, Bytes color) const
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// (For LUT profiles, I think the gamut mapping is baked into the BToA* data in the profile (?).
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// But for matrix profiles, it'd have to be done in code.)
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linear_rgb.clamp(0.f, 1.f);
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float device_r = evaluate_curve_inverse(redTRCTag, linear_rgb[0]);
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float device_g = evaluate_curve_inverse(greenTRCTag, linear_rgb[1]);
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float device_b = evaluate_curve_inverse(blueTRCTag, linear_rgb[2]);
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// FIXME: Implement curve inversion and apply inverse curve transform here.
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color[0] = round(255 * linear_rgb[0]);
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color[1] = round(255 * linear_rgb[1]);
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color[2] = round(255 * linear_rgb[2]);
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color[0] = round(255 * device_r);
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color[1] = round(255 * device_g);
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color[2] = round(255 * device_b);
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return {};
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}
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