14.16: Camera Raw's Shadows and Highlights keep tones in order

tests/CameraRawToneOrderTests.cpp

@@ -0,0 +1,72 @@
+#include "CameraRawFixtures.h"
+#include <QtTest>
+#include <cmath>
+
+// Swift 1.4.8: Shadows and Highlights keep tones in order.
+using namespace CameraRawFixtures;
+
+namespace {
+// A gray ramp, black to white, one pixel a level.
+QImage ramp()
+{
+    QImage picture = BrushRaster::context(256, 1, false);
+    for (int x = 0; x < 256; ++x)
+        picture.setPixelColor(x, 0, QColor(x, x, x));
+    return picture;
+}
+
+std::vector<int> levels(double shadows, double highlights)
+{
+    CameraRawSettings settings;
+    settings.shadows = shadows;
+    settings.highlights = highlights;
+    std::vector<int> out;
+    for (const std::array<int, 4> &pixel : pixels(settings.apply(ramp())))
+        out.push_back(pixel[1]);
+    return out;
+}
+
+// Swift's bump, u(1 - 2u)² to a half, apart.
+double bump(double u)
+{
+    return u <= 0 || u >= 0.5 ? 0 : u * (1 - 2 * u) * (1 - 2 * u);
+}
+}
+
+class CameraRawToneOrderTests : public QObject {
+    Q_OBJECT
+private slots:
+    void shadowsAndHighlightsKeepTonesInOrder();
+    void eachToneFollowsSwiftsCurve();
+};
+
+void CameraRawToneOrderTests::shadowsAndHighlightsKeepTonesInOrder()
+{
+    for (const auto &[shadows, highlights] : std::vector<std::pair<double, double>>{{100, 0}, {-100, 0}, {0, 100}, {0, -100}}) {
+        const std::vector<int> out = levels(shadows, highlights);
+        QVERIFY2(std::ranges::is_sorted(out), qPrintable(QStringLiteral("shadows %1, highlights %2").arg(shadows).arg(highlights)));
+        QVERIFY2(out[0] <= 2 && out[255] >= 253, qPrintable(QStringLiteral("black %1, white %2").arg(out[0]).arg(out[255])));
+    }
+    QVERIFY(levels(100, 0)[45] >= 45 + 20);
+}
+
+void CameraRawToneOrderTests::eachToneFollowsSwiftsCurve()
+{
+    // Gray stays gray; Highlights first, then Shadows.
+    for (const auto &[shadows, highlights] : std::vector<std::pair<double, double>>{{100, 0}, {-100, 0}, {60, 0}, {0, 100}, {0, -100}, {0, -40}, {60, -40}}) {
+        const std::vector<int> out = levels(shadows, highlights);
+        const double low = shadows / 100, high = highlights / 100;
+        for (int level = 0; level < 256; ++level) {
+            const double y = level / 255.0;
+            const double lit = std::clamp(y + high * (high >= 0 ? 1.0 : 2.5) * bump(1 - y), 0.0, 1.0);
+            const double lifted = std::clamp(lit + low * (low >= 0 ? 2.5 : 1.0) * bump(lit), 0.0, 1.0);
+            QVERIFY2(std::abs(out[size_t(level)] - std::lround(lifted * 255)) <= 1,
+                     qPrintable(QStringLiteral("%1, %2 at %3: %4").arg(shadows).arg(highlights).arg(level).arg(out[size_t(level)])));
+        }
+        // Black, middle gray and white stay where they were.
+        QVERIFY(out[0] <= 1 && std::abs(out[128] - 128) <= 1 && out[255] >= 254);
+    }
+}
+
+QTEST_MAIN(CameraRawToneOrderTests)
+#include "CameraRawToneOrderTests.moc"