opencv c ++:将图像矩阵从无符号字符转换为浮点数 [英] opencv c++: converting image matrix from unsigned char to float

问题描述

我在转换图像矩阵时遇到问题.我使用:

I have a problem with converting an image matrix. I use:

Mat image = imread(image_name, 0);

将图像读取到Mat对象中.通过调试器查看时，我看到数据存储为无符号字符.

to read an image into the Mat object. When i look through the debugger, i see the data is stored as an unsigned char.

接下来，我使用convertTo方法将数据转换为浮点值:

Next, i use convertTo method to convert the data to float values:

Mat image_f;
image.convertTo(image_f, CV_32F);

再次检查调试器，数据仍然是unsigned char类型.

Again I look through the debugger and the data is still of type unsigned char.

我在做什么错了?

推荐答案

您正在检查类型错误.对于任何图像类型，您可能都会查看image.data，该值始终为uchar*.

You're checking the type wrong. Probably you look at image.data, which will always be uchar*, for any image type.

再次尝试检查，您的类型就可以了.

Try checking again, your types will be ok.

#include <opencv2\opencv.hpp>
#include <iostream>

using namespace std;
using namespace cv;

int main()
{
    Mat image(100, 100, CV_8UC1);
    cout << image.type() << " == " << CV_8U << endl;

    Mat image_f;
    image.convertTo(image_f, CV_32F);
    cout << image_f.type() << " == " << CV_32F << endl;

    return 0;
}

您可以访问float值，例如:

#include <opencv2\opencv.hpp>
#include <iostream>

using namespace std;
using namespace cv;

int main()
{
    Mat m(10,10,CV_32FC1);

    // you can access element at row "r" and col "c" like:
    int r = 2;
    int c = 3;

    // 1
    float f1 = m.at<float>(r,c);

    // 2
    float* fData1 = (float*)m.data;
    float f2 = fData1[r*m.step1() + c];

    // 3
    float* fData2 = m.ptr<float>(0);
    float f3 = fData2[r*m.step1() + c];

    // 4
    float* fData3 = m.ptr<float>(r);
    float f4 = fData3[c];

    // 5
    Mat1f mm(m); // Or directly create like: Mat1f mm(10,10);
    float f5 = mm(r,c);

    // f1 == f2 == f3 == f4 == f5


    return 0;
}

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