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1.原理简述:
- 根据两幅图像中的一些已知对应点(控制点对),建立函数关系式,通过坐标变换,实现失真图像的几何校正。
- ![1704593-20190607214039234-614794812.jpg][]
- 设两幅图像坐标系统之间畸变关系能用解析式来描述:
- ![1704593-20190607214412623-284507974.png][]
- 根据上述的函数关系,可以依次计算畸变图像每个像素的矫正坐标值,保持各像素值不变,这样生成一幅矫正图像。
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2.实现过程:
- (1)因此首先要得到多项式,matlab提供了拟合多项式的函数 Isqcurvefit,
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** 格式**:lsqcurvefit(f,a,x,y)
- f:符号函数句柄
- a:最开始预估的值(预拟合的未知参数的估计值)。如上面的问题如果我们预估A为1,B为2,则a=\[1 2\]
- x:我们已经获知的x的值
- y:我们已经获知的x对应的y的值
- 函数的返回值为对应多项式系数组成的一维数组。
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示例(二次多项式):建立由校正图像到畸变图像的函数
- function [F] = fun(a,b)
- x = b(:,1);
- y = b(:,2);
- F = a(1)+a(2)*x+a(3)*y+a(4)*x.^2+a(5)*x.*y+a(6)*y.^2;
- end
- x0 = fixedPoints(:,1);
- y0 = fixedPoints(:,2);
- x1 = movingPoints(:,1);
- y1 = movingPoints(:,2);
- data = [x1,y1];
- a = [1 1 1 1 1 1];
- a1 = lsqcurvefit('fun',a,data,x0);
- a2 = lsqcurvefit('fun',a,data,y0);
- (2)根据得到的二项式,由校正图像每个像素坐标(x,y)出发,算出在已知畸变图像上的对应坐标(x',y'),使像元一一对应,赋予校正图像对应畸变图像的像元
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的像素值,最终得到校正图像。
示例:
- J2 = uint8(zeros(size(J)));
- for rgb = 1:3
- for i = 1:m
- for j = 1:n
- if round(fun(a1,[i,j]))>=1 && round(fun(a1,[i,j]))<=c && round(fun(a2,[i,j]))>=1 && round(fun(a2,[i,j]))<=d
- J2(i,j,rgb) = J1(round(fun(a1,[i,j])),round(fun(a2,[i,j])),rgb);
- end
- end
- end
- end
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** ** 这样生成的图像像素分布不规则,会出现像素挤压、疏密不均的现象,因此最后还需对不规则图像进行灰度内插生成规则的栅格图像。
源码:
- I = imread('sp.tif');
- J = imread('tm.tif');
- [m,n] = size(J);
- [o,p] = size(I);
- %cpselect(J,I);
- %xlswrite('data1.xls',fixedPoints);
- %xlswrite('data2.xls',movingPoints);
- %%重采样
- J1 = J(1:m/o:end,1:n/p:end,1:3);
- [c,d,q]= size(J1);
- fixedPoints = xlsread('data1.xls');
- movingPoints = xlsread('data2.xls');
- x0 = fixedPoints(:,1);
- y0 = fixedPoints(:,2);
- x1 = movingPoints(:,1);
- y1 = movingPoints(:,2);
- data = [x1,y1];
- a = [1 1 1 1 1 1];
- a1 = lsqcurvefit('fun',a,data,x0);
- a2 = lsqcurvefit('fun',a,data,y0);
- %多项式几何校正
- J2 = uint8(zeros(size(J)));
- for rgb = 1:3
- for i = 1:m
- for j = 1:n
- if round(fun(a1,[i,j]))>=1 && round(fun(a1,[i,j]))<=c && round(fun(a2,[i,j]))>=1 && round(fun(a2,[i,j]))<=d
- J2(i,j,rgb) = J1(round(fun(a1,[i,j])),round(fun(a2,[i,j])),rgb);
- end
- % J2(round(fun(a1,[i,j])),round(fun(a2,[i,j]))) = J(i,j);
- % end
- end
- end
- end
- [x,y] = size(J2);
- %根据数据游标取截取区域的左上方点
- J3 = imcrop(I,[98 180 60*o/x 60*p/y]);
- J4 = imcrop(J2,[41 80 60 60]);
- [k,y,z] = size(J3);
- [h,t,e] = size(J4);
- %%重采样
- %双线性内插法
- u = h/k;
- v = t/y;
- itp = uint8(zeros(k,y,3));
- for rgb = 1:3
- for i = ceil(1/u):k-1
- iu = floor(i*u);
- for j = ceil(1/v):y-1
- jv = floor(j*v);
- itp(i,j,rgb) = (1-(i*u-iu))*(1-(j*v-jv))*J4(iu,jv,rgb)...
- +(1-(i*u-iu))*(j*v-jv)*J4(iu,jv+1,rgb)...
- +(i*u-iu)*(1-(j*v-jv))*J4(iu+1,jv,rgb)...
- +(i*u-iu)*(j*v-jv)*J4(iu+1,jv+1,rgb);
- end
- end
- end
- %去黑边
- for rgb = 1:3
- for i = 1:3
- for j = 1:175
- itp(i,j,rgb) = J4(ceil(i*u),ceil(j*v),rgb);
- itp(145,j,rgb) = J4(43,ceil(j*v),rgb);
- end
- end
- for j = 1:2
- for i = 1:145
- itp(i,j,rgb) = J4(ceil(i*u),ceil(j*v),rgb);
- itp(i,175,rgb) = J4(ceil(i*u),61,rgb);
- end
- end
- end
- imwrite(J3,'Core1.bmp','bmp');
- imwrite(itp,'Core2.bmp','bmp');
- subplot(231),imshow(J),title('待配准图像');
- subplot(232),imshow(I),title('基准图像');
- subplot(233),imshow(J2),title('多项式几何校正后');
- subplot(234),imshow(J3),title('基准影像裁剪后');
- subplot(235),imshow(itp),title('校正影像裁剪重采样后');
- % %基准图重采样
- % kh = zuixiaogongbeishu(k,h);
- % yt = zuixiaogongbeishu(y,t);
- % u = h/kh;v = t/yt;
- % J5 = J3(1:k/kh:end,1:y/yt:end,1:3);
- % %配准图 双线性内插法重采样
- % itp = uint8(zeros(kh,yt,3));
- % for rgb = 1:3
- % for i = floor(1/u):kh-1
- % iu = floor(i*u);
- % for j = floor(1/v):yt-1
- % jv = floor(j*v);
- % itp(i,j,rgb) = (1-(i*u-iu))*(1-(j*v-jv))*J4(iu,jv,rgb)...
- % +(1-(i*u-iu))*(j*v-jv)*J4(iu,jv+1,rgb)...
- % +(i*u-iu)*(1-(j*v-jv))*J4(iu+1,jv,rgb)...
- % +(i*u-iu)*(j*v-jv)*J4(iu+1,jv+1,rgb);
- % end
- % end
- % end
- % %去黑边
- % for rgb = 1:3
- % for i = 1:144
- % for j = 1:10675
- % itp(i,j,rgb) = J4(ceil(i*u),ceil(j*v),rgb);
- % end
- % end
- % for j = 1:175
- % for i = 1:6235
- % itp(i,j,rgb) = J4(ceil(i*u),ceil(j*v),rgb);
- % end
- % end
- % end
- %
- % itp1 = uint8(zeros(6193,10615,3));
- % itp1(1:6193,1:10615,1:3) = itp(1:6193,1:10615,1:3);
- % imwrite(J5,'Crop1.bmp','bmp');
- % J5 = imread('Crop1.bmp');
- % imwrite(itp1,'Crop2.bmp','bmp');
- % J6 = imread('Crop2.bmp');
- % subplot(231),imshow(J),title('待配准图像');
- % subplot(232),imshow(I),title('基准图像');
- % subplot(233),imshow(J2),title('多项式几何校正后');
- % subplot(234),imshow(J5),title('基准影像裁剪重采样后');
- % subplot(235),imshow(J6),title('校正影像裁剪重采样后');
- % a = imread('基准.bmp');
- % b = imread('重采样后图像.bmp');
- % c = imcrop(a,[1,100,100,100]);
- % d = imcrop(b,[1,100,100,100]);
- % imwrite(c,'Core3.bmp','bmp');
- % imwrite(d,'Core4.bmp','bmp');
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