c++ - OpenCV彩色图像转灰度麻烦

Question

我是 OpenCV 的新手，我正在尝试处理目录中的图像，将其设为黑白(灰度)，然后将其写入另一个文件。但是输出图像与我预期的大不相同。也许你能帮我指出代码中的错误？

#include <iostream>
#include <opencv2/opencv.hpp>
#include <conio.h>
#include <string.h>
#include <string>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/core/core.hpp>
#include <stdio.h>
#include <stdlib.h>
#include "cuda_runtime.h"
#include "device_launch_parameters.h"

using namespace std;

void faktorial(int InSize, char *DataIn, char *DataOut)// заголовок функции
{
    for(int i = 0,  j = 0; i < InSize; i += 4, j++)
    {
        DataOut[j] = (DataIn[i] + DataIn[i + 1] + DataIn[i + 2]) / 3;
    }

}

int main() 
{        
        char* c = "E:\henrik-evensen-castle-valley-v03.jpg";

        printf("Input source of image\n Example of right directory file: E:\henrik-evensen-castle-valley-v03.jpg\n Your try:\n");
        char *tbLEN;
        tbLEN = new char [1024];

        cin.getline(tbLEN,1024);

        cout << tbLEN;


        IplImage* image;
        image = cvLoadImage(tbLEN, 1);
        int height1 = image->height;
        int width1 = image->width;
        int step = image->widthStep;
        int SizeIn = step*height1;
        char* DatIn = image->imageData;

        IplImage *image2 = cvCreateImage(cvSize(image->width, image->height), IPL_DEPTH_8U, 1);
        char* DatOut = image2->imageData;

        faktorial(SizeIn, DatIn, DatOut);

        cvNamedWindow("Imagecolor");
        cvShowImage("Imagecolor", image);

        cvNamedWindow("Gray");
        cvShowImage("Gray", image2);
        cvWaitKey(0);
        return 0;
}

编辑:我不需要 CvtColor 函数，我需要使用那个阶乘函数。

Answer 1

在 faktorial 中，您假设您有 3 个 channel 。所以你需要将 i 增加 3，而不是增加 4。另外，你需要将 char* 数据转换为 uchar* 数据，所以积累工作正常:

你最终得到:

void faktorial(int InSize, uchar *DataIn, uchar *DataOut)
{
    for (int i = 0, j = 0; i < InSize; i += 3, j++)
    {
        DataOut[j] = (DataIn[i] + DataIn[i + 1] + DataIn[i + 2]) / 3;
    }
}

您可以轻松地将其扩展到多个 channel ，例如:

void faktorial2(int InSize, int nChannels, uchar *DataIn, uchar *DataOut)
{
    for (int i = 0, j = 0; i < InSize; i += nChannels, j++)
    {
        int accum = 0;
        for (int c = 0; c < nChannels; ++c)
        {
            accum += DataIn[i + c];
        }
        DataOut[j] = uchar(accum / nChannels);
    }
}

您通常还需要考虑图像步幅:

void faktorial3(int rows, int cols, int in_step, int in_channels, int out_step, uchar *in, uchar *out)
{
    for (int r = 0; r < rows; ++r)
    {
        for (int c = 0; c < cols; ++c)
        {
            int accum = 0;
            for (int i = 0; i < in_channels; ++i)
            {
                accum += in[r*in_step + c * in_channels + i];
            }
            out[r*out_step + c] = uchar(accum / in_channels);
        }
    }
}

这里是完整的调用代码:

#include <opencv2/opencv.hpp>
using namespace std;

void faktorial3(int rows, int cols, int in_step, int in_channels, int out_step, uchar *in, uchar *out)
{
    for (int r = 0; r < rows; ++r)
    {
        for (int c = 0; c < cols; ++c)
        {
            int accum = 0;
            for (int i = 0; i < in_channels; ++i)
            {
                accum += in[r*in_step + c * in_channels + i];
            }
            out[r*out_step + c] = uchar(accum / in_channels);
        }
    }
}

void faktorial(int InSize, uchar *DataIn, uchar *DataOut)
{
    for (int i = 0, j = 0; i < InSize; i += 3, j++)
    {
        DataOut[j] = (DataIn[i] + DataIn[i + 1] + DataIn[i + 2]) / 3;
    }

}

void faktorial2(int InSize, int nChannels, uchar *DataIn, uchar *DataOut)
{
    for (int i = 0, j = 0; i < InSize; i += nChannels, j++)
    {
        int accum = 0;
        for (int c = 0; c < nChannels; ++c)
        {
            accum += DataIn[i + c];
        }
        DataOut[j] = uchar(accum / nChannels);
    }
}

int main()
{
    char tbLEN[] = "D:\\SO\\img\\barns.jpg";

    IplImage* image;
    image = cvLoadImage(tbLEN, 1);

    IplImage *image2 = cvCreateImage(cvSize(image->width, image->height), IPL_DEPTH_8U, 1);

    int height1 = image->height;
    int width1 = image->width;
    int step = image->widthStep;
    int SizeIn = step*height1;
    int nChannels = image->nChannels;
    uchar* DatIn = (uchar*)image->imageData;
    uchar* DatOut = (uchar*)image2->imageData;

    faktorial(SizeIn, DatIn, DatOut);
    //faktorial2(SizeIn, nChannels, DatIn, DatOut);
    //faktorial3(image->height, image->width, image->widthStep, image->nChannels, image2->widthStep, (uchar*)image->imageData, (uchar*)image2->imageData);

    cvNamedWindow("Imagecolor");
    cvShowImage("Imagecolor", image);

    cvNamedWindow("Gray");
    cvShowImage("Gray", image2);
    cvWaitKey(0);
    return 0;
}

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请记住，C api 已过时。 您应该切换到 C++ api。