Qt图片按原比例缩放

1.选择图片

QString strFilePath = QFileDialog::getOpenFileName(this, tr("Select file"), QStandardPaths::standardLocations(QStandardPaths::PicturesLocation), "*.png *.jpg");

if (strFilePath.isEmpty())

{

　　return;

}

2.图片合法性校验

QImageReader imgReader;

imgReader.setFileName(strFilePath);

if (!imgReader.canRead())

{

    QMessageBox::information(, "", QObject::tr("The image data is corrupt, Please select a valid one!"));

    return;

}

3.原图比例缩放

int nThumbnailWidth  = ;

int nThumbnailHeight = ;

QLable *pThumbLab = new QLabel(this);

pThumbLab->setFixedSize(nThumbnailWidth, nThumbnailHeight);

QSize sizeImage = imgReader.size();

QPixmap pixThumb(mstrPicPath);

if (sizeImage.width() > nThumbnailWidth || sizeImage.height() > nThumbnailHeight)

{

    if (sizeImage.width() > sizeImage.height())

    {

        pixThumb = pixThumb.scaledToWidth(nThumbnailWidth, Qt::SmoothTransformation);

    }

    else

    {

        pixThumb = pixThumb.scaledToHeight(nThumbnailHeight, Qt::SmoothTransformation);

    }

    pThumbLab->setFixedSize(pixThumb.size());

}

else

{

    pThumbLab->setFixedSize(sizeImage);

}

pThumbLab->setPixmap(pixThumb);