QPainter :: drawText，为每个字符获取边界框 [英] QPainter::drawText, get bounding boxes for each character

问题描述

我使用QPainter在QImage上绘制多行文本。但是，我还需要在每个字符的边框周围显示一个彩色矩形。

I'm using QPainter to draw multiline text on QImage. However, I also need to display a colored rectangle around each character's bounding box.

所以我需要知道每个字符在绘制时的边界框。

So I need to know the bounding box that each character had when being drawn.

例如，对于

painter.drawText(QRect(100, 100, 200, 200), Qt::TextWordWrap, "line\nline2", &r);

我需要得到10个矩形，考虑换行，换行，标签等。

I would need to get 10 rectangles, taking into account newlines, word-wrap, tabs, etc.

例如，第二个'l'的矩形将位于第一个'l'，而不是在'e'的右边。

For example, the rectangle of the second 'l' would be below the rectangle of the first 'l', instead of being to the right of 'e', because of the newline.

这个图片中的红色矩形的坐标（我用手把它们放在一起，所以他们不是真正的位置）：

Something like the coordinates of the red rectangles in this picture (I've put them by hand so they're not really the correct positions):

推荐答案

这可能不是最好的解决方案，但它是我能想到的最好的解决方案。

This may not be the best solution, but it's the best one I can think of.

我相信你必须自己。也就是说，不是绘制文本块，而是一次绘制一个字符。然后你可以使用QFontMetrics得到每个字符的边框。

I believe you will have to "do it yourself". That is, instead of drawing a block of text, draw each character one at a time. Then you can use QFontMetrics to get the bounding box of each character.

这是一个小工作，但不是太糟糕。类似的东西（伪代码，而不是代码）：

It's a little work, but not too bad. Something like (pseudo code, not code):

QFontMetrics fm(myFont, paintDevice);
int x = startX;
int y = startY;
for (unsigned int i = 0; i < numChars; i++)
{
    char myChar = mystr[i];  // get character to print/bound
    QRect rect = fm.boundingRect( myChar );   // get that char's bounding box
    painter.drawText(x, y, Qt::TextWordWrap, mystr[i], &r);  // output char
    painter.drawRect(...); // draw char's bounding box using 'rect'
    x += rect.width();     // advance current position horizontally

    // TODO:
    // if y > lineLen      // handle cr
    //     x = startX;
    //     y += line height

}

out QFontMetrics，它有一些不同的方法来获取边界框，最小边界框等。

Check out QFontMetrics, it has a number of different methods for getting bounding boxes, minimum bounding boxes, etc.

QFontMetrics 4.7

啊...我现在看到你使用的重载返回实际边界rect。你可以使用它，如果你喜欢跳过QFontMetrics，否则整个算法是一样的。

Ahhh... I see now that the overload you're using returns the actual bounding rect. You can just use that and skip the QFontMetrics if you like - otherwise the overall algorithm is the same.

这篇关于QPainter :: drawText，为每个字符获取边界框的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！