c++ - 在原生 C/C++ 中使用 Qt 绘制二维码

Question

我成功地在 QLabel 上绘制并显示了 QrCode，但是当我扫描它时无法识别它。这是我使用的代码 - 我制作了一个带有静态函数的小类:

void QrCodeDrawer::paintQR(QPainter &painter, const QSize sz, const QString &data, QColor fg)
{
    char *str=data.toUtf8().data();
    // NOTE: At this point you will use the API to get the encoding and format you want, instead of my hardcoded stuff:
    QrCode qr = QrCode::encodeText(str, QrCode::Ecc::HIGH);
    const int s=qr.size>0?qr.size:1;
    const double w=sz.width();
    const double h=sz.height();
    const double aspect=w/h;
    const double size=((aspect>1.0)?h:w);
    const double scale=size/(s+2);
    // NOTE: For performance reasons my implementation only draws the foreground parts in supplied color.
    // It expects background to be prepared already (in white or whatever is preferred).
    painter.setPen(Qt::NoPen);
    painter.setBrush(fg);
    for(int y=0; y<s; y++) {
        for(int x=0; x<s; x++) {
            const int color=qr.getModule(x, y);  // 0 for white, 1 for black
            if(0x0!=color) {
                const double rx1=(x+1)*scale, ry1=(y+1)*scale;
                QRectF r(rx1, ry1, scale, scale);
                painter.drawRects(&r,1);
            }
        }
    }
}

并在这里调用它:

QPixmap map(400,400);
QPainter painter(&map);
QrCodeDrawer::paintQR(painter,QSize(400,400),"Hello World", QColor("white"));
ui.qrCode->setPixmap(map);

我将“Hello World”作为输入字符串，这是我得到的代码:

我从here得到了源代码.

Answer 1

我使用了相同的示例，但遇到垃圾 QR 码问题，直到我意识到 str 可能是一个悬空指针。我将我的代码更改为此并且它工作正常:

void QrCodeDrawer::paintQR(QPainter &painter, const QSize sz, const QString &data, QColor fg)
{
    // NOTE: At this point you will use the API to get the encoding and format you want, instead of my hardcoded stuff:
    QrCode qr = QrCode::encodeText(data.toUtf8().constData(), QrCode::Ecc::HIGH);