用QPainter平铺渲染

时间:2011-11-02 12:26:40

标签: c++ qt graphics qpainter

我正在实现一个平铺渲染系统(以避免GL_MAX_VIEWPORT_DIMS - 限制)。我需要支持QWidget - 覆盖,并且必须为小部件实现平铺渲染。计划是通过使用正确的转换创建QPainter并使用“已转换的”QWidget::render调用QPainter来实现此目的。

我有一些测试代码可以做到这一点:

int w = 24;
int h = 24;
QImage tiles[4];
QPushButton btn;
btn.resize(w, h);
btn.move(w/2, h/2);
for (int i = 0; i < 2; ++i) {
  for (int j = 0; j < 2; ++j) {
    int tileidx = i + 2*j;
    tiles[tileidx] = QImage(QSize(w, h), QImage::Format_ARGB32);
    tiles[tileidx].fill(0);

    QPainter painter(&tiles[tileidx]);
    painter.setViewport(i*w,i*h, w,h); // or setWindow()
    painter.save();
    painter.translate(btn.pos());
    btn.render(&painter);
    painter.restore();
  }
}
for (int i = 0; i < 4; ++i) {
  tiles[i].save(QString("c:/temp/tile%0.bmp").arg(i));
}

我希望在每个图块中呈现按钮的四分之一,但结果却完全不同:

Tile 0 Tile 2
Tile 1 Tile 3

上面的瓷砖数字是:

0 2
1 3

如何正确设置QPainter(或实现我需要的内容)?

1 个答案:

答案 0 :(得分:0)

我最终绕过QPainter,自己进行计算并直接致电QWidget::render()

QRect viewport(i*w,j*h, w,h);
QRect intersection = viewport.intersected(widget->frameGeometry());
if (!intersection.isEmpty()) {
  QPoint target = intersection.topLeft() - viewport.topLeft();
  QPoint topLeft = widget->mapFromGlobal(intersection.topLeft());
  QPoint bottomRight = widget->mapFromGlobal(intersection.bottomRight());     
  widget->render(&paintDevice, target, QRegion(intersection));
}