翻译Python函数来敷面膜图像转换成Java

Question

我试着翻译下面的Python功能，应用于口罩，图像，到Java：

# Applies an image mask. 
def region_of_interest(img, vertices): 
    #defining a blank mask to start with 
    mask = np.zeros_like(img) 

    #defining a 3 channel or 1 channel color to fill the mask with depending on the input image 
    if len(img.shape) > 2: 
     channel_count = img.shape[2] # i.e. 3 or 4 depending on your image 
     ignore_mask_color = (255,) * channel_count 
    else: 
     ignore_mask_color = 255 

    #filling pixels inside the polygon defined by "vertices" with the fill color  
    cv2.fillPoly(mask, vertices, ignore_mask_color) 

    #returning the image only where mask pixels are nonzero 
    masked_image = cv2.bitwise_and(img, mask) 
    return masked_image 

到目前为止，这是我” ve得到了：

public static opencv_core.Mat applyMask(opencv_core.Mat image, opencv_core.MatVector vertices) { 
    opencv_core.Mat mask = opencv_core.Mat.zeros(image.size(), opencv_core.CV_8U).asMat(); 

    opencv_core.Scalar color = new opencv_core.Scalar(image.channels()); // 3 
    double[] colors = new double[] { 
    255.0, 255.0, 255.0, 255.0, 
    255.0, 255.0, 255.0, 255.0, 
    255.0, 255.0, 255.0, 255.0}; 
    color.put(colors, 0, colors.length); 

    opencv_imgproc.fillPoly(mask, vertices, color); 

    opencv_core.Mat dst = new opencv_core.Mat(); 
    opencv_core.bitwise_and(image, mask, dst); 
    return dst; 
} 

但是，它不工作。当我尝试在下面的示例中调用此方法，如：

opencv_core.MatVector points = new opencv_core.MatVector(
    new opencv_core.Mat(2, 3, opencv_core.CV_32F, new IntPointer(1, 2, 3, 4, 5, 6)) 
); 

opencv_core.MatVector vertices = new opencv_core.MatVector(points); 
opencv_core.Mat masked = LaneManager.applyMask(src, vertices); 

（我假设这是建立三个点的2x3矩阵，两个坐标每个(1,2)，(3, 4)和(5,6)正道）

我得到一个异常：

java.lang.RuntimeException: std::bad_alloc 
at org.bytedeco.javacpp.opencv_imgproc.fillPoly(Native Method) 

我使用的OpenCV作为Maven的通过由中央提供org.bytedeco.javacpp-presets:opencv-platform:3.2.0-1.3。

我必须承认我在这里感到茫然：与上面的Python函数做同样事情的惯用Java方法是什么？

Answer 1

也许一些高手有完整的答案。这里是深思：

1. Java的API是CPP API直接拷贝：http://opencv.org/opencv-java-api.html

2. 错误std::bad_alloc当你无法分配所需的存储空间出现。 （http://answers.opencv.org/question/28959/cascade-training-killed-and-bad_alloc/）

3. 有两种CPP方法：
   • C++：void fillPoly(Mat& img, const Point** pts, const int* npts, int ncontours, const Scalar& color, int lineType=LINE_8, int shift=0, Point offset=Point())和
   • C++：void fillPoly(InputOutputArray img, InputArrayOfArrays pts, const Scalar& color, int lineType=LINE_8, int shift=0, Point offset=Point())

4. 你并不需要从Mat转换为InputArray，但您可以（也应该）只通过一个Mat对象，其中InputArray请求（https://stackoverflow.com/a/32976883/1587329）

Answer 2

好吧，我终于想通了。如果你定义坐标：

int[] points = new int[] {x1, y1, x2, y2, ...}; 

然后，你可以简单地敷个面膜用下面的代码：

opencv_core.Mat mask = new opencv_core.Mat(image.size(), image.type()); 

// Array of polygons where each polygon is represented as an array of points 
opencv_core.Point polygon = new opencv_core.Point(); 
polygon.put(points, 0, points.length); 
opencv_imgproc.fillPoly(mask, polygon, new int[] {points.length/2}, 1, new opencv_core.Scalar(255, 255, 255, 0)); 

opencv_core.Mat masked = new opencv_core.Mat(image.size(), image.type()); 
opencv_core.bitwise_and(image, mask, masked); 

哪里image是原始图像，并且masked是屏蔽后的结果。

问题是没有正确定义原始点列表。