How to increase warpPerspective Or warpAffine precision?

edit

1000*cos(0.0001degree)=1000-0.0000002

translation of 0.0001 pixel

If you have a pixel with a value 256 and nearest neighbour is 0 new pixel will be 256(1-0.0001)=255.9744

Have you try with type CV_32F?

My image pixel types are CV_64F not CV_32F, consider the source image is the following: [93.0, 0.0], then translation in column with 0.1 should give me [93.0 - 9.3, 9.3], right? but it gives me the following answer: [84.28125, 8.71875]!

This is the way I create for instance one of my images:

cv::Mat srcImg = (cv::Mat_<double>(3, 3) << 0.0, 0.0, 0.0,
                                  0.0, 256.0, 0.0,
                                  0.0, 0.0, 0.0);

And when I translate in row by 0.1 this is the result:

[0.0, 0.0, 0.0,
 0.0, 232.0, 0.0,
 0.0, 24.0, 0.0]
Which is wrong!

Ok I understand your problem using this program :

cv::Mat srcImg = (cv::Mat_<double>(3, 3) << 0.0, 0.0, 0.0,
    0.0, 256.0, 0.0,
    0.0, 0.0, 0.0),dstImg;
cout<< srcImg<<endl;
vector<Point2f> srcTri(3), dstTri(3);
srcTri[0] = Point2f(0,0);
srcTri[1] = Point2f(1, 0);
srcTri[2] = Point2f(1, 1);
for (int i = 0; i <= 10; i++)
{
float dx=0.01*i;
dstTri[0] = Point2f(0+dx, 0);
dstTri[1] = Point2f(1+dx, 0);
dstTri[2] = Point2f(1+dx, 1);

cv::Mat affinite = getAffineTransform(srcTri, dstTri);
//cout<<affinite<<"\n";
warpAffine(srcImg, dstImg, affinite, Size(5,5), INTER_LINEAR);
cout<< dx<<" -> "<<dstImg.row(1)<<endl;
}

results are :

[0, 0, 0;
 0, 256, 0;
 0, 0, 0]
0 -> [0, 256, 0, 0, 0]
0.01 -> [0, 256, 0, 0, 0]
0.02 -> [0, 248, 8, 0, 0]
0.03 -> [0, 248, 8, 0, 0]
0.04 -> [0, 248, 8, 0, 0]
0.05 -> [0, 240, 16, 0, 0]
0.06 -> [0, 240, 16, 0, 0]
0.07 -> [0, 240, 16, 0, 0]
0.08 -> [0, 232, 24, 0, 0]
0.09 -> [0, 232, 24, 0, 0]
0.1 -> [0, 232, 24, 0, 0]

You see. Then, What do you think to do as a solution for this kind of problem? and knowing that these small images are only for test, my real images are quite large.