背景

    在学习AutoML或ML的过程中，需要一些图片类型的数据做分类预测训练，于是想到尝试最简单的数字识别，且单个数字的识别，也就是y的取值只有10种可能，即0到9。

以下参考代码分别考虑了数字字体的大小、数字颜色的深浅、线条的粗细、数字的倾斜、字体随机、图片背景色（纯色）的深浅、噪声点的位置和大小等要素，且进行随机生成。

代码

#include <QGuiApplication>
#include <QtCore>
#include <QtGui>
#include <QTransform>

bool createImage(int number, int size, int sn)
{
    qsrand(QTime::currentTime().msec() * sn * qrand());
    QImage img = QImage(size, size, QImage::Format_RGB32);
    QPainter painter(&img);

    //白色到灰色[0.4~1.0]
    double lightness = qAbs(qrand()) % 500/1000.0 + 0.4;
    double v = 255 * lightness;
    painter.setBrush(QBrush(QColor(v, v, v)));
    painter.drawRect(0, 0, size, size);

    //亮色字体
    int t = qAbs(qrand());
    int r = (100 + t/150) % 150;
    int g = (100 + t%150) % 150;
    QPen pen(QColor(r, g, 0));
    pen.setWidthF(qAbs(qrand() % 4)); //线宽
    painter.setPen(pen);

    //旋转
    QTransform ransform;
    ransform.rotate(qrand() % 30* (qrand() % 3 - 1));
    painter.setTransform(ransform);

    //中心点随机
    int randSize = 20 * size / 100;
    QRectF textRect(QPointF(qAbs(qrand()) % randSize, qAbs(qrand()) % randSize),
                    QSizeF(size-randSize, size-randSize));

    QString sNumber = QString::number(number);
    int fontSize = (30 + qrand() % 20) * size / 100;
    painter.setFont(QFont(qrand()%2 ? "SimSun" : "msyhbd", fontSize));
    painter.setRenderHint(QPainter::TextAntialiasing); //抗锯齿
    painter.drawText(textRect, Qt::AlignCenter, sNumber);

    //噪声点
    painter.setRenderHint(QPainter::HighQualityAntialiasing); //抗锯齿
    for (int i = 0; i < 5 + qrand() % 10; ++i)
    {
        pen.setColor(QColor(qAbs(qrand())%255, qAbs(qrand())%255, qAbs(qrand())%255));
        pen.setWidth(2 + qrand() % 4);
        painter.setPen(pen);
        painter.drawPoint(qAbs(qrand())%size, qAbs(qrand())%size);
    }

    QString fileName = QString("num_%1_%2.png").arg(sn, 6, 10, QChar('0')).arg(sNumber);
    bool ok = img.save(fileName + ".tmp", "PNG", 0);
    if (ok)
    {
        QFile::remove(fileName);
        ok = QFile::rename(fileName + ".tmp", fileName);
    }

    qDebug() << fileName << "Created!";
    return ok;
}

int main(int argc, char *argv[])
{
    QGuiApplication a(argc, argv);
    for (int i = 0; i < 100000; ++i)
    {
        createImage(qAbs(qrand())%10, 100, i);
        qDebug() << "Finish" << i;
    }
    return 0;
}

数字图片示例