如何从 SURF 描述符获取子图像的大小
我想复制由 SURF 描述符描述的图像部分。我知道 surf 中的 9x9 过滤器的比例为 1.2。因此，如果我有一个比例为 1.2 的描述符，我可以复制描述符点周围的 9x9 像素吗？如果我的比例为 1.6，我会用“9 / 1.2 * 1.6 = 12”来计算部分？子图像将是 12x12 像素？ 另一方面，我在 OpenSURF 文档中读到：
“提取 SURF 描述符的第一步是围绕兴趣点构建一个方形窗口。该窗口包含将形成描述符向量中的条目的像素，大小为 20s ，同样，其中 s 指的是检测到的比例。”
那么如果我在描述符点周围取 20*scale 像素，也许我会得到子图像？ 我不知道为什么应该是20！？我想第一个解决方案更清楚...... 谢谢！
I want to copy the part of an image which is descibed by a SURF descriptor. I know that the 9x9 filter in surf has a scale of 1.2. So if I have for example a descriptor with a scale of 1.2 is the part I can copy the 9x9 pixels around the descriptor point? And if I have a scale of 1.6 I would calculate the part with "9 / 1.2 * 1.6 = 12"? The subimage would be 12x12 pixels than?
On the other hand I read this in the OpenSURF documentation:
"The first step in extracting the SURF descriptor is to construct a square window around the interest point. This window contains the pixels which will form entries in the descriptor vector and is of size 20s, again where s refers to the detected scale."
So maybe I get the subimage if I take the 20*scale pixels around the descriptor point?
I don't know why it should be 20!? The first solution is more clear I guess...
Thanks!
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根据SURF原始论文，我可以回答你两件事：
According to SURF original paper, I can answer you with two things:
如果实现与原始 SURF 论文中描述的完全一样，则必须使用 20 秒。 9x9 是检测兴趣点的起始滤波器大小，但 20s 是描述兴趣点周围区域的窗口尺寸。
If the implementation is exactly the one described in the original SURF paper, you have to use 20s. 9x9 is the starting filter size to detect interest points, but 20s is the window dimension to describe the area around an interest point.