14.1: Color Overlay, Inner Glow and Inner Shadow recolour translucent pixels fully; Add layer effect

tests/ColorOverlayTests.cpp

@@ -0,0 +1,100 @@
+#include "Document/BrushStroke.h"
+#include "Document/LayerEffects+Renderer.h"
+#include <QtTest>
+
+// Swift's ColorOverlayTests, and the inner effects alike.
+namespace {
+QImage square(const QColor &colour, int size = 20)
+{
+    QImage image = BrushRaster::context(size, size, false);
+    image.fill(colour);
+    return image;
+}
+
+// The premultiplied RGBA bytes at the image's middle.
+std::array<int, 4> middle(const QImage &image)
+{
+    const uchar *pixel = image.constScanLine(image.height() / 2) + (image.width() / 2) * 4;
+    return {pixel[0], pixel[1], pixel[2], pixel[3]};
+}
+
+std::array<int, 4> rendered(const QImage &source, const LayerEffects &effects)
+{
+    const QImage image = LayerEffectsRenderer::render(source, std::nullopt, effects).image;
+    if (image.format() != QImage::Format_RGBA8888_Premultiplied)
+        qFatal("the renderer's format changed");
+    return middle(image);
+}
+
+bool near(const std::array<int, 4> &pixel, const std::array<int, 4> &expected, int tolerance)
+{
+    for (int channel = 0; channel < 4; ++channel) {
+        if (std::abs(pixel[channel] - expected[channel]) > tolerance)
+            return false;
+    }
+    return true;
+}
+
+QString text(const std::array<int, 4> &pixel)
+{
+    return QStringLiteral("%1 %2 %3 %4").arg(pixel[0]).arg(pixel[1]).arg(pixel[2]).arg(pixel[3]);
+}
+}
+
+class ColorOverlayTests : public QObject {
+    Q_OBJECT
+private slots:
+    void overlayRecolorsTranslucentPixelsAndKeepsTheirAlpha();
+    void overlayOpacityMixesWithTheLayersOwnColor();
+    void overlayLeavesTheShadowBeneathTranslucentPixels();
+    void innerEffectsRecolourTranslucentPixelsAndKeepTheirAlpha();
+};
+
+void ColorOverlayTests::overlayRecolorsTranslucentPixelsAndKeepsTheirAlpha()
+{
+    // Half-clear black under white: half-clear white, no grey band.
+    LayerEffects effects;
+    effects.colorOverlay = ColorOverlayEffect{.red = 1, .green = 1, .blue = 1, .opacity = 1};
+    const std::array<int, 4> pixel = rendered(square(QColor(0, 0, 0, 128)), effects);
+    QVERIFY2(near(pixel, {128, 128, 128, 128}, 1), qPrintable(text(pixel)));
+}
+
+void ColorOverlayTests::overlayOpacityMixesWithTheLayersOwnColor()
+{
+    LayerEffects effects;
+    effects.colorOverlay = ColorOverlayEffect{.red = 0, .green = 0, .blue = 1, .opacity = 0.5};
+    const std::array<int, 4> pixel = rendered(square(QColor(255, 0, 0)), effects);
+    QVERIFY2(near(pixel, {128, 0, 128, 255}, 1), qPrintable(text(pixel)));
+}
+
+void ColorOverlayTests::overlayLeavesTheShadowBeneathTranslucentPixels()
+{
+    // A red shadow under half-clear black stays red beneath.
+    LayerEffects effects;
+    effects.colorOverlay = ColorOverlayEffect{.red = 1, .green = 1, .blue = 1, .opacity = 1};
+    effects.shadow = ShadowEffect{.angle = 90, .distance = 0, .blur = 0, .red = 1, .green = 0, .blue = 0, .opacity = 1};
+    const std::array<int, 4> pixel = rendered(square(QColor(0, 0, 0, 128)), effects);
+    QVERIFY2(near(pixel, {192, 128, 128, 192}, 1), qPrintable(text(pixel)));
+}
+
+void ColorOverlayTests::innerEffectsRecolourTranslucentPixelsAndKeepTheirAlpha()
+{
+    const QImage half = square(QColor(0, 0, 0, 128));
+    // A glow a hair wide falls by half.
+    LayerEffects shadowed;
+    shadowed.innerShadow = InnerShadowEffect{.angle = 0, .distance = 60, .blur = 0.01, .red = 1, .green = 0, .blue = 0, .opacity = 1};
+    std::array<int, 4> pixel = rendered(half, shadowed);
+    QVERIFY2(near(pixel, {128, 0, 0, 128}, 1), qPrintable(text(pixel)));
+    // A hair-wide glow falls by what the shape lacks: half.
+    LayerEffects glowing;
+    glowing.innerGlow = InnerGlowEffect{.size = 0.01, .red = 1, .green = 1, .blue = 1, .opacity = 1};
+    pixel = rendered(half, glowing);
+    QVERIFY2(near(pixel, {64, 64, 64, 128}, 1), qPrintable(text(pixel)));
+    // A shadow beneath stays untinted.
+    shadowed.shadow = ShadowEffect{.angle = 90, .distance = 0, .blur = 0, .red = 0, .green = 0, .blue = 1, .opacity = 1};
+    pixel = rendered(half, shadowed);
+    QVERIFY2(near(pixel, {128, 0, 64, 192}, 1), qPrintable(text(pixel)));
+}
+
+QTEST_GUILESS_MAIN(ColorOverlayTests)
+#include "ColorOverlayTests.moc"