qt - 如何将 QImage 裁剪到其不透明区域？

Question

如果我有一个带有 alpha 通道的 QImage，如何创建一个新的 QImage，它被裁剪到不透明区域的边界框？

Answer 1

I found another SO answer (in C++) that does this:

Does Qt have a way to find bounding box of an image?

def bbox(p):
    bounding-box-of-an-image
    l = p.width()
    t = p.height()
    r = 0
    b = 0

    for y in range(p.height()):
        rowFilled = False
        for x in range(p.width()):
            if qAlpha(p.pixel(x, y)):
                rowFilled = True
                r = max(r, x)
                if l > x:
                    l = x
        if rowFilled:
            t = min(t, y)
            b = y
    return QRect(QPoint(l, t), QPoint(r, b))

but it would be great if there were a better/faster way to do this.

Answer 2

您要实现的是图像处理的一部分。这不是 QImage 中的标准操作。您必须遍历像素并计算边界框。我建议您使用 cv libs 因为它们对此类操作很有用。