Question

我正在尝试在QLabel Widge中旋转89x89图像。

#include "header.h"

disc::disc(QWidget *Parent) : QWidget(Parent)
{
    orig_pixmap = new QPixmap();
    rotate = new QLabel(this);
    showDegrees = new QLabel(this);

    orig_pixmap->load("pic.png");
    degrees = 0;

    rotate->resize(89,89);
    rotate->move(100,10);
    rotate->setStyleSheet("QLabel{background-color:red;}");

    showDegrees->resize(100,100);
    showDegrees->move(400,0);
}

void disc::rotate_disc()
{
    QString string;
    degrees++;
    if(degrees == 360) degrees = 0;

    QTransform rotate_disc;

    rotate_disc.translate( (orig_pixmap->width()-rotate->width())/2 , (orig_pixmap->width()-rotate->height())/2);
    rotate_disc.rotate(degrees,Qt::ZAxis);

    QPixmap pixmap;
    //pixmap = orig_disc->scaled(89,89,Qt::IgnoreAspectRatio,Qt::SmoothTransformation);
    pixmap = orig_pixmap->transformed(rotate_disc,Qt::SmoothTransformation);
    rotate->setPixmap(pixmap);

    string.append("Degrees: " + QString::number(degrees) + "*");
    showDegrees->setText(string);
}

即使它旋转。图像的一半在QLabel外部滚动，因此该侧面不可见。如何使其在图像中心的原点（0,0）处居中旋转。

这是文件

http://www65.zippyshare.com/v/85775455/file.html

如果你看一下，你可以看到图像就像向左边弹跳一样。我可以让它在黑色区域内旋转。

我将每10ms的信号超时设置为rotate_disc（）函数。我正在用它来学习Qt深入研究。

谢谢！

Answer 1

我这样做了......

//Move windows's coordinate system to center.
QTransform transform_centerOfWindow( 1, 0, 0, 1, width()/2, height()/2 );

//Rotate coordinate system.
transform_centerOfWindow.rotate( m_LoadingDisk_degrees );

//Draw image with offset to center of image.
QPainter painter( this );

//Transform coordinate system.
painter.setTransform( transform_centerOfWindow );

//Load image.

//Notice: As coordinate system is set at center of window, we have to center the image also... so the minus offset to come to center of image.
painter.drawPixmap( -loadingDisk.width()/2, -loadingDisk.height()/2, loadingDisk );

Answer 2

我认为你真正缺少的是围绕像素图中心旋转的初始平移。

将其移至原点，旋转，然后向后移动。请记住，根据您在代码中指定转换的方式，转换按照您期望的方式以相反的顺序应用。

QTransform rotate_disc;
rotate_disc.translate(orig_pixmap->width()/2.0 , orig_pixmap->height()/2.0);
rotate_disc.rotate(degrees);
rotate_disc.translate(-orig_pixmap->width()/2.0 , -orig_pixmap->height()/2.0);

Answer 3

如果您正在制作加载指示器，动画gif会更容易。见GIF animation in Qt

无法让图像在Qt中心旋转

3 个答案: