opencv estimateRigidTransform:如何获得全局缩放? [英] opencv estimateRigidTransform: How to get global scale?
问题描述
我使用openCV的estimateRigidTransform来稳定一系列视频帧,效果非常好。
I'm using openCV's estimateRigidTransform to stabilize a series of video frames, which works very well.
该函数返回一个2x3转换矩阵M:
The function returns a 2x3 transformation matrix M:
| a_11 a_12 b_1 |
| -a_12 a_11 b_2 |
据我所知, b
代表翻译, a
元素用于缩放和旋转。
As far as I understand the b
elements represent the translation, and the a
elements are used to do the scaling and rotation.
我想要do,是从M获取全局缩放 - 表示相机缩放因子的值。如何从 a
值正确计算?
What I would like to do, is get global scale from M - a value that represents the camera zooming factor. How can I do calculate this correctly from a
values?
为了澄清一点我想得到的,这里是一个例子。让我们说estimateRigidTransform计算下面第二帧关于第一帧的变换矩阵M:
To clarify a little more what I want to get, here is an example. Let's say estimateRigidTransform calculates a transformation matrix M for the second frame below regarding to the first frame:
在这种情况下,全局缩放因子应该是aroud 2.我的问题是如何从M? p>
The global zooming factor in this case should be aroud 2. My question is how to get this value from M?
推荐答案
确定,额外搜索后,我发现了一个很好的答案: http://math.stackexchange.com/questions/13150/extracting-rotation-scale-values-from-2d-transformation-matrix
Ok, after additional search I found a great answer here: http://math.stackexchange.com/questions/13150/extracting-rotation-scale-values-from-2d-transformation-matrix
其中缩放由s_x和s_y表示。这两个值大部分是相等的(因为摄像机拍摄的视频在两个方向上都是相等的),所以我可以选择其中一个。
Where the "zooming" is represented by s_x and s_y. These two values will mostly be equal (since zoom in video captured by cameras is equal in both directions), so I can take either one.
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