问题描述
我正在使用Python和Opencv。我现在正在进行车牌识别项目。我现在可以识别这样的盘子：
I am using Python and Opencv. I am now doing a license-plate recognition project. I can now recognize the plate like this:
我得到一个像这样的数组：
And I got an "array" like this :
[[[542 796]]
[[965 883]]
[[547 884]]
[[966 795]]]
问题是：如何用这些坐标裁剪出边界区域？
The problem is: How can I crop out the bound region with these coordinates?
因为四个corrdinates是置换，它不是一个矩形，所以我不知道如何裁剪出来。
As the four corrdinates are permuted and it is not a rectangle, so I dont know how I can crop this out.
推荐答案
你可以裁剪内部矩形或外边界矩形。让四个坐标为： -
You can crop the inner rectangle or outer bounding rectangle. Let the four co-ordinates be:-
（x1，y1），（x2，y2）
(x1,y1), (x2,y2)
（x3，y3），（x4，y4）
(x3,y3), (x4,y4)
假设您对外边界矩形感兴趣，因此没有字母被分割，您可以使用下面的方法进行简单裁剪投资回报率。
Assuming, you are interested in outer bounding rectangle, so that no letter is segmented, you can do simple cropping using below ROI.
int topLeftX = min(x1,x3);
int topLeftY = min(y1, y2);
int width = max(x2, x4) - topLeftX;
int height = max(y3, y4) - topLeftY;
cv::Rect outerRoi(topLeftX, topLeftY, width, height);
cv::Mat roiImage = image(outerRoi); //Note that this will not create a deep copy
如果对最适合梯形的矩形感兴趣在里面，你应该用最大值交换min，反之亦然。
If interested in largest rectangle which fits the trapezium from inside, you should swap min with max and vice-versa.
如果你想要像roi这样的梯形，你应该创建一个蒙版图像。有关更多说明，请参阅
If you want a trapezium like roi, you should create a mask image. For further directions,, see copying non-rectangular roi opencv
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