英文:
How can I rotate the QBitmap nicely while still drawing the position accurately?
问题
我想在任意点上绘制一个 QBitmap。
例如，我想在 QBitmap 上绘制一个 点 (5, 5)，以匹配屏幕上的 点 (10, 10)。
我还想改变围绕该点的 QBitmap 的角度，但如果我旋转它，绘图将失去位置。
如何在保持准确绘制的同时使 QBitmap 旋转得好看？
英文:
I want to draw a QBitmap over an arbitrary point.
For example, I want to draw a point (5, 5) on the QBitmap to match a point (10,10) on the screen.
I also want to change the angle of the QBitmap around that point, but if I rotate it, the drawing will be out of position.
How can I rotate the QBitmap nicely while still drawing the position accurately?
bool MyApp::eventFilter(QObject *obj, QEvent *event)
{
QBitmap qBmp = QBitmap(".\\pix1.bmp");
int iPixX = 10;
int iPixY = 10;
int iDrawPointX = 5;
int iDrawPointY = 5;
if( event->type() == QEvent::Paint ) {
QPainter painter(m_pUi->drawLayer);
painter.setPen( QPen(Qt::black) );
painter.translate(iPixX, iPixY);
painter.rotate(45);
painter.translate(iPixX - iDrawPointX, iPixY - iDrawPointX);
painter.drawPixmap(0, 0, qBmp);
}
painter.end();
return true;
}
return false;
}
答案1
得分: 1
Translate the following code to position your bitmap in screen coordinates:
# 将位图定位到屏幕坐标上：
painter.translate(iPixX - iDrawPointX, iPixY - iDrawPointY);
Make translation to position the bitmap at the point which is the origin of the rotation operation (this is the step you missed; the (5,5) coordinates of the bitmap will be the rotation origin point):
# 进行平移以将位图定位到旋转操作的原点（这是您忽略的步骤，位图的坐标（5,5）将成为旋转的原点）：
painter.translate(-iPixX, -iPixY);
Make rotation:
# 进行旋转：
painter.rotate(45);
Back to screen coordinates position:
# 返回到屏幕坐标位置：
painter.translate(iPixX, iPixY);
The full code:
# 完整代码：
painter.translate(iPixX, iPixY);
painter.rotate(45);
painter.translate(-iPixX, -iPixY);
painter.translate(iPixX - iDrawPointX, iPixY - iDrawPointY);
英文:
Make translation to position your bitmap in screen coordinates:
painter.translate(iPixX - iDrawPointX,iPixY - iDrawPointY);
Make translation to position the bitmap in the point which is the origin of rotation operation (this is your missed step, (5,5) coord of bitmap will be rotation origin point):
painter.translate(-iPixX, -iPixY);
Make rotation:
painter.rotate(45);
Back to screen coordinates position:
painter.translate(iPixX, iPixY);
The full code:
painter.translate(iPixX, iPixY);
painter.rotate(45);
painter.translate(-iPixX, -iPixY);
painter.translate(iPixX - iDrawPointX,iPixY - iDrawPointY);
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