如何解决使用 C++ 和 opencv 进行图像缩放的样条 Catmull-Rom
我正在尝试使用 C++ 和 OpenCV 实现用于图像缩放的样条 Catmull-Rom。 我进行了两次测试，第一个是图像缩放（X2），第二个是图像重建（缩放图像抽取）。 我的问题是在插入的图像中出现一些白色和黑色像素（image1），当我显示像素值时，我发现白色像素具有负值，黑色像素的值大于 255，也是重建的图像显得模糊（image2 和 image3）。
float CalCurveInt(float t,float p0,float p1,float p2,float p3)
{
float t2 = t * t;
float t3 = t2 * t;
float x = 0.5f * ((2.0f * p1) +
(-p0 + p2) * t +
(2.0f * p0 - 5.0f * p1 + 4 * p2 - p3) * t2 +
(-p0 + 3.0f * p1 - 3.0f * p2 + p3) * t3);
return x;
}
Mat CalcCatmull(Mat &src,int zoom)
{
int v1,v2,v3,v4,Ptr,Xmax,Ymax;
float Result,t,c1,c2,c3,c4;
//------------------------------------------------------------
Xmax = src.cols;
Ymax = src.rows;
Size srcSize(zoom*Xmax,Ymax);
Mat dst(srcSize,CV_8UC1);
for (int j = 0; j < Ymax; j++)
{
Ptr = 0;
for (int i = 0; i < Xmax; i++)
{
v1 = i - 1; v2 = i; v3 = i + 1; v4 = i + 2;
if (i - 1 < 0) v1 = 0;
if (Xmax <= i + 1) v3 = Xmax - 1;
if (Xmax <= i + 2) v4 = Xmax - 1;
for (double J = 1; J <= zoom; J++)
{
t = J / zoom;
Result = 0.0;
c1 = src.at<uchar>(j,v1);
c2 = src.at<uchar>(j,v2);
c3 = src.at<uchar>(j,v3);
c4 = src.at<uchar>(j,v4);
Result = CalCurveInt(t,c4);
dst.at<uchar>(j,Ptr) = abs(Result);
Ptr++;
}
}
}
//------------------------------------------------
Xmax = dst.cols;
Ymax = dst.rows;
Size srcSize1(Xmax,zoom*Ymax);
Mat dest(srcSize1,CV_8UC1);
for (int i = 0; i < Xmax; i++)
{
Ptr = 0;
for (int j = 0; j < Ymax; j++)
{
v1 = j - 1; v2 = j; v3 = j + 1; v4 = j + 2;
if (j - 1 < 0) v1 = 0;
if (Ymax <= j + 1) v3 = Ymax - 1;
if (Ymax <= j + 2) v4 = Ymax - 1;
for (double J = 1; J <= zoom; J++)
{
t = J / zoom;
Result = 0.0;
c1 = dst.at<uchar>(v1,i);
c2 = dst.at<uchar>(v2,i);
c3 = dst.at<uchar>(v3,i);
c4 = dst.at<uchar>(v4,i);
Result = CalCurveInt(t,c4);
dest.at<uchar>(Ptr,i) = Result;
Ptr++;
}
}
}
return dest;
}
float zoom = 2.0;
int main()
{
Mat src = imread("fruits.png",CV_LOAD_IMAGE_GRAYSCALE);
int width = src.cols;
int hight = src.rows;
/*Image decimation*/
Size srcdSize(int(width / zoom),int(hight / zoom));
Mat srcd;
pyrDown(src,srcd,srcdSize);
imshow("decimation",srcd);
Mat dst = CalcCatmull(srcd,zoom);
imshow("Image Source",src);
imshow("Image dest",dst);
imwrite("Image dest.png",dst);
waitKey(0);
return 0;
}
提前致谢。
解决方法
我的旧实现，似乎运行良好。
#include <iostream>
#include <vector>
#include <stdio.h>
#include <stdarg.h>
#include "opencv2/opencv.hpp"
#include "fstream"
#include "iostream"
using namespace std;
using namespace cv;
//-----------------------------------------------------------------------------------------------------
// Take 2 points,compute values between p1 and p2,p0 and p3 need for tangents computation
// on the bouunds. Parameter t - changes in range 0 to 1 (0 - we are in p1,1 - we are in p2)
//-----------------------------------------------------------------------------------------------------
void PointOnCurve(Point2f &out,float t,Point2f p0,Point2f p1,Point2f p2,Point2f p3)
{
float t2 = t * t;
float t3 = t2 * t;
out.x = 0.5f * ( ( 2.0f * p1.x ) + ( -p0.x + p2.x ) * t +
( 2.0f * p0.x - 5.0f * p1.x + 4 * p2.x - p3.x ) * t2 +
( -p0.x + 3.0f * p1.x - 3.0f * p2.x + p3.x ) * t3 );
out.y = 0.5f * ( ( 2.0f * p1.y ) + ( -p0.y + p2.y ) * t +
( 2.0f * p0.y - 5.0f * p1.y + 4 * p2.y - p3.y ) * t2 +
( -p0.y + 3.0f * p1.y - 3.0f * p2.y + p3.y ) * t3 );
}
//-----------------------------------------------------------------------------------------------------
// interpolation of 4х4 patch
//
// S * S * S * S
// * * * * * * *
// S * S * S * S
// * * * * * * *
// S * S * S * S
// * * * * * * *
// S * S * S * S
//
// S- pixels of source imgage
//
// sequentially take 2 middle columns and computte D.
//
// S * 1 * 2 * S
// * * * * * * *
// S * 1 * 2 * S
// * * D * D * *
// S * 1 * 2 * S
// * * * * * * *
// S * 1 * 2 * S
//
// same for rows and we will have F
//
// S * S * S * S
// * * * * * * *
// 3 * 3 F 3 * 3
// * * D * D * *
// 4 * 4 F 4 * 4
// * * * * * * *
// S * S * S * S
//
// then compute diagonals and after averafing with neihbours will find С
//
// 1 * S * S * 2
// * * * * * * *
// S * 1 F 2 * S
// * * D C D * *
// S * 2 F 1 * S
// * * * * * * *
// 2 * S * S * 1
//-----------------------------------------------------------------------------------------------------
void PointOnSurface(Mat& src,Mat& dst)
{
float t=0.5;
Point2f out;
dst=Mat(3,3,CV_32FC1);
// Угловые точки результата совпадают с точками центральной ячейки исходного патча
dst.at<float>(0,0)=src.at<float>(1,1);
dst.at<float>(2,0)=src.at<float>(2,1);
dst.at<float>(0,2)=src.at<float>(1,2);
dst.at<float>(2,2)=src.at<float>(2,2);
Point2f p0;
Point2f p1;
Point2f p2;
Point2f p3;
p0.x=0;p0.y=src.at<float>(0,1);
p1.x=1;p1.y=src.at<float>(1,1);
p2.x=2;p2.y=src.at<float>(2,1);
p3.x=3;p3.y=src.at<float>(3,1);
PointOnCurve(out,t,p0,p1,p2,p3);
dst.at<float>(1,0)=out.y;
p0.x=0;p0.y=src.at<float>(0,2);
p1.x=1;p1.y=src.at<float>(1,2);
p2.x=2;p2.y=src.at<float>(2,2);
p3.x=3;p3.y=src.at<float>(3,2);
PointOnCurve(out,2)=out.y;
p0.x=0;p0.y=src.at<float>(1,0);
p1.x=1;p1.y=src.at<float>(1,1);
p2.x=2;p2.y=src.at<float>(1,2);
p3.x=3;p3.y=src.at<float>(1,3);
PointOnCurve(out,p3);
dst.at<float>(0,1)=out.y;
p0.x=0;p0.y=src.at<float>(2,0);
p1.x=1;p1.y=src.at<float>(2,2);
p3.x=3;p3.y=src.at<float>(2,3);
PointOnCurve(out,p3);
dst.at<float>(2,1)=out.y;
// diagonals
// 1
p0.x=0;p0.y=src.at<float>(0,p3);
float d1=out.y;
// 2
p0.x=0;p0.y=src.at<float>(3,2);
p3.x=3;p3.y=src.at<float>(0,p3);
float d2=out.y;
// averaging
dst.at<float>(1,1)=1.0/6.0*(d1+d2+dst.at<float>(0,1)+dst.at<float>(1,0)+dst.at<float>(1,2)+dst.at<float>(2,1));
}
//-----------------------------------------------------------------------------------------------------
//
//-----------------------------------------------------------------------------------------------------
//-----------------------------------------------------------------------------------------------------
void Scale2Times(Mat& src_img,Mat &dstImg)
{
Mat imgf,img;
Mat dst;
Mat src;
src_img.convertTo(imgf,CV_32FC1,1.0/255.0);
cv::copyMakeBorder(imgf,img,1,cv::BORDER_REFLECT);
dstImg=Mat(src_img.rows*2,src_img.cols*2,CV_32FC1);
for(int i=0;i<img.rows-4;i++)
{
for(int j=0;j<img.cols-4;j++)
{
img(Rect(j,i,4,4)).copyTo(src);
PointOnSurface(src,dst);
dst.copyTo(dstImg(Rect(2*j+1,2*i+1,3)));
}
}
dstImg=dstImg(Rect(0,dstImg.cols-2,dstImg.rows-2)).clone();
}
//-----------------------------------------------------------------------------------------------------
//
//-----------------------------------------------------------------------------------------------------
int main( int argc,char** argv )
{
namedWindow("Src");
namedWindow("cvResize");
namedWindow("Catmul-Rom");
Mat Img=imread("C:\\ImagesForTest\\1.tiff",0);
imshow("Src",Img);
Mat dstImg;
Scale2Times(Img,dstImg);
imshow("Catmul-Rom",dstImg);
Mat ImgLin(Img.rows*2,Img.cols*2,CV_8UC1);
cv::resize(Img,ImgLin,Size(Img.cols*2,Img.rows*2),INTER_CUBIC);
imshow("cvResize",ImgLin);
waitKey(0);
//getchar();
return 0;
}
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