qt5base-lts/tests/benchmarks/gui/image/qimageconversion/tst_qimageconversion.cpp

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#include <qtest.h>
#include <QImage>


class tst_QImageConversion : public QObject
{
    Q_OBJECT
private slots:
    void convertRgb888ToRGB32_data();
    void convertRgb888ToRGB32();

private:
    QImage generateImageRgb888(int width, int height);
};

void tst_QImageConversion::convertRgb888ToRGB32_data()
{
    QTest::addColumn<QImage>("inputImage");
    // height = 5000 to get interesting timing.

    // 3 pixels wide -> smaller than regular vector of 128bits
    QTest::newRow("width: 3px; height: 5000px;") << generateImageRgb888(3, 5000);

    // 8 pixels wide -> potential for 2 vectors
    QTest::newRow("width: 8px; height: 5000px;") << generateImageRgb888(3, 5000);

    // 16 pixels, minimum for the SSSE3 implementation
    QTest::newRow("width: 16px; height: 5000px;") << generateImageRgb888(16, 5000);

    // 50 pixels, more realistic use case
    QTest::newRow("width: 50px; height: 5000px;") << generateImageRgb888(50, 5000);

    // 2000 pixels -> typical values for pictures
    QTest::newRow("width: 2000px; height: 5000px;") << generateImageRgb888(2000, 5000);
}

void tst_QImageConversion::convertRgb888ToRGB32()
{
    QFETCH(QImage, inputImage);

    QBENCHMARK {
        volatile QImage output = inputImage.convertToFormat(QImage::Format_RGB32);
        // we need the volatile and the following to make sure the compiler does not do
        // anything stupid :)
        (void)output;
    }
}

/*
 Fill a RGB888 image with "random" pixel values.
 */
QImage tst_QImageConversion::generateImageRgb888(int width, int height)
{
    QImage image(width, height, QImage::Format_RGB888);
    const int byteWidth = width * 3;

    for (int y = 0; y < image.height(); ++y) {
        uchar *scanline = image.scanLine(y);
        for (int x = 0; x < byteWidth; ++x)
            scanline[x] = x ^ y;
    }
    return image;
}

QTEST_MAIN(tst_QImageConversion)
#include "tst_qimageconversion.moc"