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Reduce range of gamma and gain in the color grading filter
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As suggested here:
https://forum.shotcut.org/t/color-grading-wheels-sensitivity-curve/36563
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@bmatherly
bmatherly committed Jan 15, 2025
1 parent fcdd9c6 commit 5a7f090
Showing 1 changed file with 86 additions and 44 deletions.
130 changes: 86 additions & 44 deletions src/qml/filters/color/ui.qml
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2014-2024 Meltytech, LLC
* Copyright (c) 2014-2025 Meltytech, LLC
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
Expand All @@ -20,12 +20,10 @@ import QtQuick.Layouts
import Shotcut.Controls as Shotcut

Item {

// For a = 0, the function is linear
// The solution to the quadratic formula reduces to:
property var defaultParameters: ['lift_r', 'lift_g', 'lift_b', 'gamma_r', 'gamma_g', 'gamma_b', 'gain_r', 'gain_g', 'gain_b']
property double gammaFactor: 2
property double gainFactor: 4
property double _gammaFactorV0: 2
property double _gainFactorV0: 4
property int _filterVersion: 1
property bool blockUpdate: true

function loadValues() {
Expand All @@ -38,12 +36,12 @@ Item {
liftRedSpinner.value = filter.getDouble("lift_r", position) * 100;
liftGreenSpinner.value = filter.getDouble("lift_g", position) * 100;
liftBlueSpinner.value = filter.getDouble("lift_b", position) * 100;
gammaRedSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gamma_r", position), gammaFactor));
gammaGreenSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gamma_g", position), gammaFactor));
gammaBlueSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gamma_b", position), gammaFactor));
gainRedSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gain_r", position), gainFactor));
gainGreenSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gain_g", position), gainFactor));
gainBlueSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gain_b", position), gainFactor));
gammaRedSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gamma_r", position), _gammaFactorV0));
gammaGreenSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gamma_g", position), _gammaFactorV0));
gammaBlueSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gamma_b", position), _gammaFactorV0));
gainRedSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gain_r", position), _gainFactorV0));
gainGreenSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gain_g", position), _gainFactorV0));
gainBlueSpinner.value = wheelToSpinner(scaleValueToWheel(filter.getDouble("gain_b", position), _gainFactorV0));
liftKeyframesButton.checked = filter.keyframeCount('lift_r') > 0;
gammaKeyframesButton.checked = filter.keyframeCount('gamma_r') > 0;
gainKeyframesButton.checked = filter.keyframeCount('gain_r') > 0;
Expand All @@ -55,6 +53,47 @@ Item {
}

function scaleWheelToValue(w, f) {
if (_filterVersion == 0)
return scaleWheelToValueV0(w, f);
else
return scaleWheelToValueV1(w);
}

function scaleValueToWheel(v, f) {
if (_filterVersion == 0)
return scaleValueToWheelV0(v, f);
else
return scaleValueToWheelV1(v);
}

function scaleWheelToValueV1(w) {
// Scaling function for filter version 1
// The color wheel value (w) range is [0.0 - 1.0]. For the gamma and gain
// parameters, we want to scale that to [0.5 - 2]
// With the following point mappings:
// f(0) = 0.5
// f(0.5) = 1.0 (no change)
// f(1) = 2
if (w < 0.5)
return 0.5 + w;
if (w == 0.5)
return 1.0;
return w * 2
}

function scaleValueToWheelV1(v) {
// Scaling function for filter version 1
// Do the opposite of scaleWheelToValueV1
if (v < 1.0)
return v - 0.5;
if (v == 1.0)
return 0.5;
if (v > 1.0)
return v / 2.0
}

function scaleWheelToValueV0(w, f) {
// Scaling function for filter version 0
// The color wheel value (w) range is [0.0 - 1.0]. For the gamma and gain
// gain parameters, we want to scale that to [0.0 - f] where (f) is the
// maximum scaling factor. The middle of the wheel (0.5) needs to map to
Expand All @@ -74,8 +113,9 @@ Item {
return a * (w * w) + b * w;
}

function scaleValueToWheel(v, f) {
// Do the opposite of scaleWheelToValue
function scaleValueToWheelV0(v, f) {
// Scaling function for filter version 0
// Do the opposite of scaleWheelToValueV0
var a = (2 * f) - 4;
var b = f - a;
if (a == 0)
Expand Down Expand Up @@ -108,8 +148,10 @@ Item {
filter.set("gain_r", 1);
filter.set("gain_g", 1);
filter.set("gain_b", 1);
filter.set("shotcut:filter_version", 1);
filter.savePreset(defaultParameters);
}
_filterVersion = filter.getDouble("shotcut:filter_version");
loadValues();
// The color wheel widgets' colorChanged signals are queued between
// threads and trigger after loadValues() has set blockUpdate false.
Expand Down Expand Up @@ -220,13 +262,13 @@ Item {
filter.resetProperty('gamma_g');
filter.resetProperty('gamma_b');
if (checked) {
filter.set('gamma_r', scaleWheelToValue(gammawheel.redF, gammaFactor), getPosition());
filter.set('gamma_g', scaleWheelToValue(gammawheel.greenF, gammaFactor), getPosition());
filter.set('gamma_b', scaleWheelToValue(gammawheel.blueF, gammaFactor), getPosition());
filter.set('gamma_r', scaleWheelToValue(gammawheel.redF, _gammaFactorV0), getPosition());
filter.set('gamma_g', scaleWheelToValue(gammawheel.greenF, _gammaFactorV0), getPosition());
filter.set('gamma_b', scaleWheelToValue(gammawheel.blueF, _gammaFactorV0), getPosition());
} else {
filter.set('gamma_r', scaleWheelToValue(gammawheel.redF, gammaFactor));
filter.set('gamma_g', scaleWheelToValue(gammawheel.greenF, gammaFactor));
filter.set('gamma_b', scaleWheelToValue(gammawheel.blueF, gammaFactor));
filter.set('gamma_r', scaleWheelToValue(gammawheel.redF, _gammaFactorV0));
filter.set('gamma_g', scaleWheelToValue(gammawheel.greenF, _gammaFactorV0));
filter.set('gamma_b', scaleWheelToValue(gammawheel.blueF, _gammaFactorV0));
}
filter.endUndoCommand();
}
Expand Down Expand Up @@ -258,13 +300,13 @@ Item {
filter.resetProperty('gain_g');
filter.resetProperty('gain_b');
if (checked) {
filter.set('gain_r', scaleWheelToValue(gainwheel.redF, gainFactor), getPosition());
filter.set('gain_g', scaleWheelToValue(gainwheel.greenF, gainFactor), getPosition());
filter.set('gain_b', scaleWheelToValue(gainwheel.blueF, gainFactor), getPosition());
filter.set('gain_r', scaleWheelToValue(gainwheel.redF, _gainFactorV0), getPosition());
filter.set('gain_g', scaleWheelToValue(gainwheel.greenF, _gainFactorV0), getPosition());
filter.set('gain_b', scaleWheelToValue(gainwheel.blueF, _gainFactorV0), getPosition());
} else {
filter.set('gain_r', scaleWheelToValue(gainwheel.redF, gainFactor));
filter.set('gain_g', scaleWheelToValue(gainwheel.greenF, gainFactor));
filter.set('gain_b', scaleWheelToValue(gainwheel.blueF, gainFactor));
filter.set('gain_r', scaleWheelToValue(gainwheel.redF, _gainFactorV0));
filter.set('gain_g', scaleWheelToValue(gainwheel.greenF, _gainFactorV0));
filter.set('gain_b', scaleWheelToValue(gainwheel.blueF, _gainFactorV0));
}
filter.endUndoCommand();
}
Expand Down Expand Up @@ -331,14 +373,14 @@ Item {
filter.resetProperty('gamma_r');
filter.resetProperty('gamma_g');
filter.resetProperty('gamma_b');
filter.set('gamma_r', scaleWheelToValue(gammawheel.redF, gammaFactor));
filter.set('gamma_g', scaleWheelToValue(gammawheel.greenF, gammaFactor));
filter.set('gamma_b', scaleWheelToValue(gammawheel.blueF, gammaFactor));
filter.set('gamma_r', scaleWheelToValue(gammawheel.redF, _gammaFactorV0));
filter.set('gamma_g', scaleWheelToValue(gammawheel.greenF, _gammaFactorV0));
filter.set('gamma_b', scaleWheelToValue(gammawheel.blueF, _gammaFactorV0));
} else {
var position = getPosition();
filter.set('gamma_r', scaleWheelToValue(gammawheel.redF, gammaFactor), position);
filter.set('gamma_g', scaleWheelToValue(gammawheel.greenF, gammaFactor), position);
filter.set('gamma_b', scaleWheelToValue(gammawheel.blueF, gammaFactor), position);
filter.set('gamma_r', scaleWheelToValue(gammawheel.redF, _gammaFactorV0), position);
filter.set('gamma_g', scaleWheelToValue(gammawheel.greenF, _gammaFactorV0), position);
filter.set('gamma_b', scaleWheelToValue(gammawheel.blueF, _gammaFactorV0), position);
}
filter.endUndoCommand();
}
Expand Down Expand Up @@ -368,14 +410,14 @@ Item {
filter.resetProperty('gain_r');
filter.resetProperty('gain_g');
filter.resetProperty('gain_b');
filter.set('gain_r', scaleWheelToValue(gainwheel.redF, gainFactor));
filter.set('gain_g', scaleWheelToValue(gainwheel.greenF, gainFactor));
filter.set('gain_b', scaleWheelToValue(gainwheel.blueF, gainFactor));
filter.set('gain_r', scaleWheelToValue(gainwheel.redF, _gainFactorV0));
filter.set('gain_g', scaleWheelToValue(gainwheel.greenF, _gainFactorV0));
filter.set('gain_b', scaleWheelToValue(gainwheel.blueF, _gainFactorV0));
} else {
var position = getPosition();
filter.set('gain_r', scaleWheelToValue(gainwheel.redF, gainFactor), position);
filter.set('gain_g', scaleWheelToValue(gainwheel.greenF, gainFactor), position);
filter.set('gain_b', scaleWheelToValue(gainwheel.blueF, gainFactor), position);
filter.set('gain_r', scaleWheelToValue(gainwheel.redF, _gainFactorV0), position);
filter.set('gain_g', scaleWheelToValue(gainwheel.greenF, _gainFactorV0), position);
filter.set('gain_b', scaleWheelToValue(gainwheel.blueF, _gainFactorV0), position);
}
filter.endUndoCommand();
}
Expand Down Expand Up @@ -632,14 +674,14 @@ Item {
filter.set('lift_b', liftwheel.blueF * 2 - 1, position);
break;
case 'gamma_r':
filter.set('gamma_r', scaleWheelToValue(gammawheel.redF, gammaFactor), position);
filter.set('gamma_g', scaleWheelToValue(gammawheel.greenF, gammaFactor), position);
filter.set('gamma_b', scaleWheelToValue(gammawheel.blueF, gammaFactor), position);
filter.set('gamma_r', scaleWheelToValue(gammawheel.redF, _gammaFactorV0), position);
filter.set('gamma_g', scaleWheelToValue(gammawheel.greenF, _gammaFactorV0), position);
filter.set('gamma_b', scaleWheelToValue(gammawheel.blueF, _gammaFactorV0), position);
break;
case 'gain_r':
filter.set('gain_r', scaleWheelToValue(gainwheel.redF, gainFactor), position);
filter.set('gain_g', scaleWheelToValue(gainwheel.greenF, gainFactor), position);
filter.set('gain_b', scaleWheelToValue(gainwheel.blueF, gainFactor), position);
filter.set('gain_r', scaleWheelToValue(gainwheel.redF, _gainFactorV0), position);
filter.set('gain_g', scaleWheelToValue(gainwheel.greenF, _gainFactorV0), position);
filter.set('gain_b', scaleWheelToValue(gainwheel.blueF, _gainFactorV0), position);
break;
}
}
Expand Down

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