Question

我正在寻找将图像像素数据提取到整数列表（或任何数字表示）中。例如，具有2×2白色图像，结果将是[255,255,255,255]。如果图像是生成代码而不是从磁盘读取，Mat.dump（）方法会准确地打印图像像素值：

    Mat m = new Mat(5, 10, CvType.CV_8UC1, new Scalar(0));
    System.out.println("OpenCV Mat: " + m);
    Mat mr1 = m.row(1);
    mr1.setTo(new Scalar(1));
    Mat mc5 = m.col(5);
    mc5.setTo(new Scalar(5));
    System.out.println("OpenCV Mat data, "+m.total()+" elements:\n" + 
    m.dump());

准确打印=＆gt;

    OpenCV Mat: Mat [ 5*10*CV_8UC1, isCont=true, isSubmat=false, 
    nativeObj=0x1415d50, dataAddr=0x13a6880 ]
    OpenCV Mat data, 50 elements:
    [  0,   0,   0,   0,   0,   5,   0,   0,   0,   0;
       1,   1,   1,   1,   1,   5,   1,   1,   1,   1;
       0,   0,   0,   0,   0,   5,   0,   0,   0,   0;
       0,   0,   0,   0,   0,   5,   0,   0,   0,   0;
       0,   0,   0,   0,   0,   5,   0,   0,   0,   0]

但如果我写Mat＆＃34; m＆＃34;磁盘上的内容，然后我再次读取它，dump（）方法吐出奇怪的输出：

    Imgcodecs.imwrite(TRAIN_PATH_PROC+"m.jpg",m);

    m = null;
    m = Imgcodecs.imread(TRAIN_PATH_PROC+"m.jpg");
    System.out.println("Fresly read m, "+m.total()+" elements:\n"+m.dump());

打印

Fresly read m, 50 elements:
[  0,   0,   0,   0,   0,   0,   0,   0,   0,   1,   1,   1,   0,   0,   0,   
5,   5,   5,   1,   1,   1,   0,   0,   0,   0,   0,   0,   0,   0,   0;
1,   1,   1,   1,   1,   1,   1,   1,   1,   1,   1,   1,   1,   1,   1,   
5,   5,   5,   1,   1,   1,   1,   1,   1,   1,   1,   1,   1,   1,   1;
0,   0,   0,   0,   0,   0,   0,   0,   0,   1,   1,   1,   0,   0,   0,   5,   
5,   5,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0;
0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   4,   
4,   4,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0;
0,   0,   0,   0,   0,   0,   0,   0,   0,   1,   1,   1,   0,   0,   0,   
5,   5,   5,   1,   1,   1,   0,   0,   0,   0,   0,   0,   0,   0,   0]

由于我需要从读取的图像中提取int值，并依赖dump（）来表示字符串，这会给我带来麻烦。

修改

我设法使用

简单地提取数据

    List<Integer> values = new ArrayList<>();

    for (int i = 0; i < m.rows(); i++) {
        for (int j = 0; j < m.cols(); j++) {
            values.add((int)m.get(i,j)[0]);
        }
    }

Answer 1

Mat.dump（）是我们的朋友，就像打印垫子名称以显示其属性一样。（问题标题应更改为不贬低dump（）。）imread自动假定已转换为BGR，因此转换为3通道数据，而不是预期的1通道。 imwrite JPEG自动压缩。您可以控制未读转换并减少压缩，但这仍然有一些损耗。

MatOfInt imwrite_flags = new MatOfInt();
imwrite_flags.fromArray(Imgcodecs.IMWRITE_JPEG_QUALITY , 100);
Imgcodecs.imwrite(TRAIN_PATH_PROC+"m.jpg",m, imwrite_flags);

m = Imgcodecs.imread(TRAIN_PATH_PROC+"m.jpg", Imgcodecs.IMREAD_UNCHANGED);

您需要无压缩或无损压缩，因此请使用TIFF格式-下面结合TIFF进行示例。（请参见Is there a way to set specific compression scheme when saving tiff file in opencv?）

String TRAIN_PATH_PROC = "";

Mat m = new Mat(5, 10, CvType.CV_8UC1, new Scalar(0));
System.out.println("OpenCV Mat: " + m);
Mat mr1 = m.row(1);
mr1.setTo(new Scalar(1));
Mat mc5 = m.col(5);
mc5.setTo(new Scalar(5));
System.out.println("OpenCV Mat data, "+m.total()+" elements:\n" + 
m.dump());

MatOfInt imwrite_flags = new MatOfInt();
imwrite_flags.fromArray(Imgcodecs.IMWRITE_TIFF_COMPRESSION , 1); // no compression
Imgcodecs.imwrite(TRAIN_PATH_PROC+"m2.tif",m, imwrite_flags);// note name change so both examples can run
// OR
Imgcodecs.imwrite(TRAIN_PATH_PROC+"m.tif",m); // default compression LZW grayscale but lossless, I think

m = null;
m = Imgcodecs.imread(TRAIN_PATH_PROC+"m.tif", Imgcodecs.IMREAD_UNCHANGED);
System.out.println("OpenCV Mat: " + m);
System.out.println("Fresly read m, "+m.total()+" elements:\n"+m.dump());

Mat.dump（）的OpenCV java实现返回不准确的数据

1 个答案: