在 OpenCV 中实现 DCT 时出错

error in implementation of dct in opencv

本文关键字：出错 DCT 实现 OpenCV      更新时间：2023-10-16

为什么当我尝试在OpenCV中实现DCT时会出现以下错误？ 

Assertion failed (type == CV_32FC1 || type == CV_64FC1) in dct,

这是代码：

#include <cv.h>
#include "opencv2/imgproc/imgproc.hpp"
#include <highgui.h>
#include <iostream>
using namespace cv;
using namespace std;
int main()
{
    Mat image,dimage(image);
       image = imread( "lena.jpg", 1 );
      if( !image.data )
        {
          printf( "No image data n" );
           return -1;
         }
        namedWindow( "Display Image", CV_WINDOW_AUTOSIZE );
        imshow( "Display Image", image );
        dimage=Mat::zeros(image.rows,image.cols,CV_32F);
        dct(image, dimage, DCT_INVERSE == 0 );
        namedWindow( "DCT Image", CV_WINDOW_AUTOSIZE );
        imshow( "DCT image", dimage );
        waitKey(0);
       return 0;
}

您必须先将图像从 uchar 转换为浮点（稍后可能再转换回 uchar）：

// also please use the c++ headers, not the old c-ones !
#include "opencv2/core/core.hpp" 
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
Mat image = imread( "lena.jpg", 0 ); // grayscale
Mat fimage;
image.convertTo(fimage, CV_32F, 1.0/255); // also scale to [0..1] range (not mandatory)
// you're lucky with lena (512x512), for odd sizes, you have to 
// pad it to pow2 size, or use dft() instead:
Mat dimage;
dct( fimage, dimage ); 
// process dimage,
// then same way back:
dct( dimage, dimage, DCT_INVERSE );
dimage.convertTo(image, CV_8U); // maybe scale back to [0..255] range (depending on your processing)
imshow("result",image);
waitKey();
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