java 使用 mat.get() 的像素的 OpenCV 颜色值有时会返回 null
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OpenCV color-value of a pixel by using mat.get() returns sometimes null
提问by Paket2001
I try to get the RGB Values of a pixel using mat.get(inx, int y) on Android and OpenCV 2.4.4.
我尝试在 Android 和 OpenCV 2.4.4 上使用 mat.get(inx, int y) 获取像素的 RGB 值。
Mat img = Utils.loadResource(getBaseContext(), R.drawable.ex3);
double[] tmp = img.get(100, 100);
if(printLog) Log.v(tag, "Color: "+ tmp[0] +","+ tmp[1] +","+ tmp[2] +"");
Normaly I got the tmp-Array returned. But at some pixels, i got returned "null". (That points are in range of the picture!)
通常我得到了返回的 tmp-Array。但是在某些像素处，我得到了“null”的返回。（这些点在图片范围内！）
So why I get at some coordinates a array and on some others "null" and how to fix that?
那么为什么我在某些坐标上得到一个数组而在其他一些坐标上得到“null”以及如何解决这个问题？
回答by Paket2001
At OpenCV by getting pixelinformations with Mat.get(row, col) the meaning of X and Y is changed: Use Y for the row and X for the col.
在 OpenCV 中，通过使用 Mat.get(row, col) 获取像素信息，X 和 Y 的含义发生了变化：对行使用 Y，对列使用 X。
Mat.get(Y, X);
So in my case I was out of range but openCV did not return a Exception. It returns "null"
所以在我的情况下，我超出了范围，但 openCV 没有返回异常。它返回“空”
回答by Dan
I'd first check how many channels your Matgot with Mat::channels()and then access to them through:
我会首先检查您使用Mat了多少个频道Mat::channels()，然后通过以下方式访问它们：
double[] tmp = img.at(100,100);
双[] tmp = img.at(100,100);
回答by GPrathap
To access each pixel separately you can do this if you are using https://github.com/bytedeco/javacv
要单独访问每个像素，如果您使用的是https://github.com/bytedeco/javacv，则可以执行此操作
IplImage image = cvLoadImage("path/to/image/get.jpg");
public void colorProcess(IplImage image){
CvMat result = CvMat.create(image.width(),image.height(), CV_32F);
CvMat ff =image.asCvMat();
for(int a=0;a<result.cols();a++){
for(int b=0;b<result.rows();b++){
CvScalar rgb = cvGet2D(ff, a, b);
System.out.println("blue "+rgb.getVal(0)+"green "+rgb.getVal(1)+"red "+rgb.getVal(2));
}
}
}
