Filter › Dither, as Compositor 1.3.3 (12.15)
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#include "Document/BrushStroke.h"
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#include "Document/Dither.h"
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#include "Document/EditorSession.h"
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#include <QtTest>
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#include <set>
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// Swift 1.3.3's Dither: the model and the kernel through `apply`.
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namespace {
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QImage filled(int width, int height, QColor colour)
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{
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QImage image = BrushRaster::context(width, height, false);
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image.fill(colour);
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return image;
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}
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// A horizontal ramp of grays, left black, right white.
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QImage ramp(int width, int height)
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{
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QImage image = BrushRaster::context(width, height, false);
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for (int y = 0; y < height; ++y)
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for (int x = 0; x < width; ++x)
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image.setPixelColor(x, y, QColor::fromRgbF(float(x) / float(width - 1), float(x) / float(width - 1), float(x) / float(width - 1)));
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return image;
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}
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std::set<QRgb> colours(const QImage &image)
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{
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std::set<QRgb> found;
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for (int y = 0; y < image.height(); ++y)
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for (int x = 0; x < image.width(); ++x)
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found.insert(image.pixel(x, y));
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return found;
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}
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DitherSettings style(DitherStyle each, double pixelSize = 1)
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{
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DitherSettings settings;
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settings.style = each;
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settings.pixelSize = pixelSize;
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return settings;
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}
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}
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class DitherTests : public QObject {
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Q_OBJECT
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private slots:
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void stylesKeepSwiftsNamesOrderAndGroups();
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void normalizingClampsRoundsAndTrimsTheCharacters();
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void bayerThresholdsAGrayIntoItsPattern();
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void diffusionMakesTwoTonesOrMore();
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void twoColorsAndTheOriginalOnes();
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void alphaIsKeptAndClearPixelsLeftAlone();
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void chunkyPixelsFillTheirBlocks();
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void dotsLeaveTheirCornersToTheDarkColour();
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void marksDrawLightOnDarkOrDarkOnLight();
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void glyphsAreSortedByTheirInk();
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void densityAndContrastMoveTheThreshold();
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void theScreenTurnsWithItsAngle();
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void asciiDrawsWithItsOwnCharacters();
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};
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void DitherTests::stylesKeepSwiftsNamesOrderAndGroups()
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{
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QStringList names;
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for (const DitherStyle each : allDitherStyles)
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names << rawValue(each);
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QCOMPARE(names, (QStringList{"Atkinson (Classic Mac)", "Floyd–Steinberg", "Bayer 2 × 2", "Bayer 4 × 4", "Bayer 8 × 8", "Halftone Dots",
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"Halftone Lines", "Halftone Diamonds", "Mac Patterns", "ASCII"}));
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QString groups;
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for (const DitherStyle each : allDitherStyles)
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groups += QString::number(ditherGroup(each));
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QCOMPARE(groups, QString("0011122233"));
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QVERIFY(diffuses(DitherStyle::floydSteinberg) && !diffuses(DitherStyle::bayer2));
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QVERIFY(hasTones(DitherStyle::bayer8) && !hasTones(DitherStyle::dots));
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QVERIFY(isHalftone(DitherStyle::diamonds) && !isHalftone(DitherStyle::patterns));
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QVERIFY(drawsMarks(DitherStyle::ascii) && drawsMarks(DitherStyle::lines) && !drawsMarks(DitherStyle::atkinson));
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QCOMPARE(rawValue(DitherPixelShape::dot), QString("Dot"));
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QCOMPARE(rawValue(DitherColors::twoColors), QString("Two Colors"));
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// Chunky square pixels, 1-bit Atkinson, glowing marks by default.
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const DitherSettings defaults;
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QVERIFY(defaults.style == DitherStyle::atkinson && defaults.pixelSize == 2 && defaults.pixelShape == DitherPixelShape::square);
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QVERIFY(defaults.levels == 2 && defaults.lightOnDark && defaults.colors == DitherColors::blackWhite);
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}
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void DitherTests::normalizingClampsRoundsAndTrimsTheCharacters()
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{
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DitherSettings wild;
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wild.pixelSize = 40.6;
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wild.cellSize = 2;
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wild.angle = std::nan("");
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wild.levels = 4.5;
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wild.diffusion = -5;
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wild.density = 300;
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wild.contrast = std::numeric_limits<double>::infinity();
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wild.dark = AdjustmentColor(-1, 0.5, 2);
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wild.light = AdjustmentColor(3, -2, 0.25);
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wild.characters = QStringLiteral("ab\ncd\r\ne\u2028f\u000Bg\u000Ch\u0085i\u2029\t j") + QString(80, u'x');
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const DitherSettings normal = wild.normalized();
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QCOMPARE(normal.pixelSize, 32.0);
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QCOMPARE(normal.cellSize, 4.0);
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QCOMPARE(normal.angle, 45.0);
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QCOMPARE(normal.levels, 5.0);
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QCOMPARE(normal.diffusion, 0.0);
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QCOMPARE(normal.density, 100.0);
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QCOMPARE(normal.contrast, 0.0);
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QVERIFY(normal.dark == AdjustmentColor(0, 0.5, 1) && normal.light == AdjustmentColor(1, 0, 0.25));
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// Every line break goes, tabs and spaces stay; 64 kept.
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QCOMPARE(normal.characters, QStringLiteral("abcdefghi\t j") + QString(52, u'x'));
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// A grapheme of many units counts once, never split.
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DitherSettings emoji;
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emoji.characters = QString(63, u'.') + QStringLiteral("\U0001F44D\U0001F3FD") + QStringLiteral("zz");
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QCOMPARE(emoji.normalized().characters, QString(63, u'.') + QStringLiteral("\U0001F44D\U0001F3FD"));
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QCOMPARE(DitherSettings().normalized(), DitherSettings());
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}
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void DitherTests::bayerThresholdsAGrayIntoItsPattern()
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{
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// Half gray over Bayer 2 × 2: high thresholds light.
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const QImage out = style(DitherStyle::bayer2).apply(filled(4, 4, QColor(128, 128, 128)));
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const QRgb black = qRgb(0, 0, 0), white = qRgb(255, 255, 255);
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const std::array<QRgb, 4> pattern{black, white, white, black};
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for (int y = 0; y < 4; ++y)
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for (int x = 0; x < 4; ++x)
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QCOMPARE(out.pixel(x, y), pattern[size_t((y & 1) * 2 + (x & 1))]);
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// Four tones on a ramp: 0, 85, 170, 255 alone.
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DitherSettings tones = style(DitherStyle::bayer4);
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tones.levels = 4;
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std::set<int> levels;
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const QImage toned = tones.apply(ramp(64, 8));
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for (int x = 0; x < 64; ++x)
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levels.insert(qRed(toned.pixel(x, 3)));
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QCOMPARE(levels, (std::set<int>{0, 85, 170, 255}));
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}
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void DitherTests::diffusionMakesTwoTonesOrMore()
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{
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for (const DitherStyle each : {DitherStyle::atkinson, DitherStyle::floydSteinberg}) {
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const QImage out = style(each).apply(ramp(64, 16));
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QCOMPARE(colours(out), (std::set<QRgb>{qRgb(0, 0, 0), qRgb(255, 255, 255)}));
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// More white towards the light end.
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int left = 0, right = 0;
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for (int y = 0; y < 16; ++y) {
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for (int x = 0; x < 16; ++x) {
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left += qRed(out.pixel(x, y)) == 255;
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right += qRed(out.pixel(63 - x, y)) == 255;
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}
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}
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QVERIFY2(left < 40 && right > 216, qPrintable(QStringLiteral("%1 %2").arg(left).arg(right)));
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}
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// No diffusion: a flat mid gray rounds whole.
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DitherSettings flat = style(DitherStyle::atkinson);
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flat.diffusion = 0;
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QCOMPARE(colours(flat.apply(filled(8, 8, QColor(140, 140, 140)))), (std::set<QRgb>{qRgb(255, 255, 255)}));
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}
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void DitherTests::twoColorsAndTheOriginalOnes()
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{
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DitherSettings two = style(DitherStyle::bayer8);
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two.colors = DitherColors::twoColors;
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two.dark = AdjustmentColor(0.2, 0, 0.4);
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two.light = AdjustmentColor(1, 0.8, 0.6);
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QCOMPARE(colours(two.apply(ramp(32, 8))), (std::set<QRgb>{qRgb(51, 0, 102), qRgb(255, 204, 153)}));
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// Original: red stays red, dithered on its own channels.
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DitherSettings original = style(DitherStyle::bayer8);
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original.colors = DitherColors::original;
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for (const QRgb each : colours(original.apply(filled(8, 8, QColor(255, 0, 0)))))
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QCOMPARE(each, qRgb(255, 0, 0));
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}
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void DitherTests::alphaIsKeptAndClearPixelsLeftAlone()
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{
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QImage image = ramp(16, 4);
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image.setPixelColor(0, 0, Qt::transparent);
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image.setPixelColor(5, 1, QColor::fromRgbF(1, 1, 1, 0.5f));
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const QImage out = style(DitherStyle::floydSteinberg).apply(image);
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QCOMPARE(out.pixelColor(0, 0).alpha(), 0);
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QCOMPARE(out.pixelColor(5, 1).alpha(), 128);
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for (int x = 1; x < 16; ++x)
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QCOMPARE(out.pixelColor(x, 3).alpha(), 255);
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}
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void DitherTests::chunkyPixelsFillTheirBlocks()
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{
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const QImage out = style(DitherStyle::bayer8, 4).apply(ramp(18, 10));
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QCOMPARE(out.size(), QSize(18, 10));
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// One colour a 4 × 4 block; edge blocks cut.
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for (int y = 0; y < 10; ++y)
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for (int x = 0; x < 18; ++x)
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QCOMPARE(out.pixel(x, y), out.pixel(x / 4 * 4, y / 4 * 4));
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QCOMPARE(colours(out.copy(0, 0, 16, 8)), (std::set<QRgb>{qRgb(0, 0, 0), qRgb(255, 255, 255)}));
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// A cut block averages in the clear beyond the edge.
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QCOMPARE(out.pixelColor(17, 0).alpha(), 128);
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QCOMPARE(out.pixelColor(0, 9).alpha(), 128);
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QCOMPARE(out.pixelColor(17, 9).alpha(), 64);
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// Diffused small: each block's exact average, then its pixel.
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const QImage source = ramp(18, 10);
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QImage averaged = BrushRaster::context(5, 3, false);
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for (int y = 0; y < 3; ++y) {
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for (int x = 0; x < 5; ++x) {
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std::array<int, 4> sum{};
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for (int sy = y * 4; sy < std::min(10, y * 4 + 4); ++sy)
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for (int sx = x * 4; sx < std::min(18, x * 4 + 4); ++sx)
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for (int channel = 0; channel < 4; ++channel)
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sum[size_t(channel)] += source.constScanLine(sy)[sx * 4 + channel];
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for (int channel = 0; channel < 4; ++channel)
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averaged.scanLine(y)[x * 4 + channel] = uchar((sum[size_t(channel)] + 8) / 16);
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}
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}
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const QImage small = style(DitherStyle::floydSteinberg).apply(averaged);
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const QImage chunky = style(DitherStyle::floydSteinberg, 4).apply(source);
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for (int y = 0; y < 10; ++y)
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for (int x = 0; x < 18; ++x)
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QCOMPARE(chunky.pixel(x, y), small.pixel(x / 4, y / 4));
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// A block's average: half black, half white reads as gray.
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QImage halves = BrushRaster::context(8, 8, false);
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for (int y = 0; y < 8; ++y)
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for (int x = 0; x < 8; ++x)
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halves.setPixelColor(x, y, x % 2 ? Qt::white : Qt::black);
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DitherSettings levels = style(DitherStyle::bayer2, 8);
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levels.levels = 3;
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QCOMPARE(colours(levels.apply(halves)), (std::set<QRgb>{qRgb(128, 128, 128)}));
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}
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void DitherTests::dotsLeaveTheirCornersToTheDarkColour()
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{
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DitherSettings dots = style(DitherStyle::bayer2, 8);
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dots.pixelShape = DitherPixelShape::dot;
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const QImage out = dots.apply(filled(16, 16, Qt::white));
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// White dots on black, each centred in its block.
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QCOMPARE(out.pixel(0, 0), qRgb(0, 0, 0));
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QCOMPARE(out.pixel(4, 4), qRgb(255, 255, 255));
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QCOMPARE(out.pixel(8, 15), qRgb(0, 0, 0));
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QCOMPARE(out.pixel(12, 12), qRgb(255, 255, 255));
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// Two Colors: the gaps are the dark one.
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dots.colors = DitherColors::twoColors;
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dots.dark = AdjustmentColor(0, 0, 1);
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QCOMPARE(dots.apply(filled(16, 16, Qt::white)).pixel(0, 0), qRgb(0, 0, 255));
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// Square pixels have no gaps.
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dots.pixelShape = DitherPixelShape::square;
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QCOMPARE(dots.apply(filled(16, 16, Qt::white)).pixel(0, 0), qRgb(255, 255, 255));
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}
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void DitherTests::marksDrawLightOnDarkOrDarkOnLight()
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{
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for (const DitherStyle each : {DitherStyle::dots, DitherStyle::lines, DitherStyle::diamonds, DitherStyle::patterns, DitherStyle::ascii}) {
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DitherSettings marks = style(each);
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const QImage glowing = marks.apply(ramp(64, 64));
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// Hard marks, but for the characters' smoothed ink.
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if (each == DitherStyle::ascii) {
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for (const QRgb colour : colours(glowing))
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QVERIFY(qRed(colour) == qGreen(colour) && qGreen(colour) == qBlue(colour));
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} else {
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QCOMPARE(colours(glowing), (std::set<QRgb>{qRgb(0, 0, 0), qRgb(255, 255, 255)}));
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}
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marks.lightOnDark = false;
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const QImage inked = marks.apply(ramp(64, 64));
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QVERIFY2(inked != glowing, qPrintable(rawValue(each)));
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// Black stays black, white white, either way.
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QCOMPARE(qRed(glowing.pixel(0, 32)), 0);
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QCOMPARE(qRed(inked.pixel(63, 32)), 255);
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}
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}
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void DitherTests::glyphsAreSortedByTheirInk()
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{
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const DitherSettings::Glyphs glyphs = DitherSettings::glyphs(QStringLiteral("@. .#"), 8);
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// Four distinct: space, dot, hash, at; 8 × 8 maps.
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QCOMPARE(glyphs.coverage.size(), size_t(4));
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QCOMPARE(glyphs.maps.size(), size_t(4 * 64));
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QCOMPARE(glyphs.coverage[0], 0.0f);
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QVERIFY(glyphs.coverage[1] > 0 && glyphs.coverage[1] < glyphs.coverage[2] && glyphs.coverage[2] <= glyphs.coverage[3]);
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QVERIFY(*std::max_element(glyphs.maps.begin() + 192, glyphs.maps.end()) > 200);
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QCOMPARE(DitherSettings::glyphs(DitherSettings::defaultCharacters(), 12).coverage.size(), size_t(10));
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// A 20-pixel cell: M at 23 pixels, 15–19 tall.
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const std::vector<uint8_t> m = DitherSettings::glyphs(QStringLiteral("M"), 20).maps;
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int top = 20, bottom = -1;
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bool smooth = false;
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for (int index = 0; index < 400; ++index) {
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if (m[size_t(index)] > 128) {
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top = std::min(top, index / 20);
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bottom = std::max(bottom, index / 20);
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}
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smooth = smooth || (m[size_t(index)] > 0 && m[size_t(index)] < 255);
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}
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QVERIFY2(bottom - top + 1 >= 15 && bottom - top + 1 <= 19, qPrintable(QString::number(bottom - top + 1)));
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QVERIFY(smooth);
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// Centred on its ink both ways: a dot mid cell.
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const std::vector<uint8_t> dot = DitherSettings::glyphs(QStringLiteral("."), 20).maps;
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double sum = 0, sumX = 0, sumY = 0;
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for (int index = 0; index < 400; ++index) {
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sum += dot[size_t(index)];
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sumX += dot[size_t(index)] * (index % 20 + 0.5);
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sumY += dot[size_t(index)] * (index / 20 + 0.5);
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}
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QVERIFY2(std::abs(sumX / sum - 10) < 0.6 && std::abs(sumY / sum - 10) < 0.6, qPrintable(QStringLiteral("%1 %2").arg(sumX / sum).arg(sumY / sum)));
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// Canonically equal graphemes are one, as Swift's Characters.
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QCOMPARE(DitherSettings::glyphs(QStringLiteral("\u00E9e\u0301"), 20).coverage.size(), size_t(1));
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}
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void DitherTests::densityAndContrastMoveTheThreshold()
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{
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// Bayer 8 × 8 on flat gray: whites follow tone.
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const auto whites = [](int gray, double density, double contrast) {
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DitherSettings settings = style(DitherStyle::bayer8);
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settings.density = density;
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settings.contrast = contrast;
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const QImage out = settings.apply(filled(8, 8, QColor(gray, gray, gray)));
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int count = 0;
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for (int y = 0; y < 8; ++y)
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for (int x = 0; x < 8; ++x)
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count += qRed(out.pixel(x, y)) == 255;
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return count;
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};
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// Density: gamma 2^(1.5 d), more ink as it rises.
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QCOMPARE(whites(128, 0, 0), 32);
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QCOMPARE(whites(128, 50, 0), 20);
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QCOMPARE(whites(128, -50, 0), 42);
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// Contrast pivots on mid gray, steeper as it rises.
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QCOMPARE(whites(153, 0, 0), 38);
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QCOMPARE(whites(153, 0, 50), 44);
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QCOMPARE(whites(153, 0, -50), 35);
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}
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void DitherTests::theScreenTurnsWithItsAngle()
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{
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// Halftone lines at 0°: rows alike; at 90°: columns alike.
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for (const double angle : {0.0, 90.0}) {
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DitherSettings lines = style(DitherStyle::lines);
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lines.angle = angle;
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lines.cellSize = 8;
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const QImage out = lines.apply(filled(32, 32, QColor(100, 100, 100)));
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bool alike = true, varied = false;
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for (int a = 0; a < 32; ++a) {
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for (int b = 0; b < 32; ++b) {
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const QRgb here = angle == 0 ? out.pixel(b, a) : out.pixel(a, b);
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alike = alike && here == (angle == 0 ? out.pixel(0, a) : out.pixel(a, 0));
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varied = varied || here != out.pixel(0, 0);
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}
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}
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QVERIFY2(alike && varied, qPrintable(QString::number(angle)));
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}
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}
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void DitherTests::asciiDrawsWithItsOwnCharacters()
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{
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DitherSettings ascii = style(DitherStyle::ascii);
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ascii.cellSize = 12;
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const QImage source = ramp(48, 24);
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// A blank alphabet marks nothing: all the dark paper.
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ascii.characters = QStringLiteral(" ");
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QCOMPARE(colours(ascii.apply(source)), (std::set<QRgb>{qRgb(0, 0, 0)}));
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// None at all: Swift's default alphabet.
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ascii.characters = QString();
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const QImage fallback = ascii.apply(source);
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ascii.characters = DitherSettings::defaultCharacters();
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QCOMPARE(fallback, ascii.apply(source));
|
||||
// Another alphabet draws otherwise.
|
||||
ascii.characters = QStringLiteral(" #");
|
||||
QVERIFY(ascii.apply(source) != fallback);
|
||||
}
|
||||
|
||||
QTEST_MAIN(DitherTests)
|
||||
#include "DitherTests.moc"
|
||||
Reference in new issue
Block a user