Is there any way to correct the fisheye of a single image？

[Adarine99]

Hi Everyone, I need to correct the fisheye of a single image，how to get the result in this project? Thanks

[brmarkus]

Do you find an example (e.g. ffmpeg or gstreamer) under the "https://github.com/intel/libxcam/wiki/Tests" Test section, with de-warping?

[zongwave]

You can use unit tests (GLES and CPU version) to do fisheye correction. you probably need to create a map table according to your camera.

https://github.com/intel/libxcam/wiki/Tests#4-test-gles-handler 2) Remap test $ test-gles-handler --type remap --input0 input0.nv12 --output output.nv12 --in-w 1280 --in-h 800 --out-w 1280 --out-h 800 --save true --loop 1000

https://github.com/intel/libxcam/wiki/Tests#6-test-soft-image 1) Remap test $ test-soft-image --type remap --input0 input0.nv12 --output output.nv12 --in-w 1280 --in-h 800 --out-w 1280 --out-h 800 --save true --loop 1000

[Adarine99]

Hi, In "test-gles-handler " remap means to flip the image,so I'm trying to do some change as below:

static void calc_undistortion_table (uint32_t width, uint32_t height, struct ocam_model *ocam_model,PointFloat2 *&map_table,float sf)
{
    int i,j;
    float Nxc = height/2.0;
    float Nyc = width/2.0;
    float Nz  = -width/sf;
    double M[3];
    double m[2];
    for (i=0; i<height; i++)
    {
        PointFloat2 *lineT = &map_table[i * width];
        for (j=0; j<width; j++)
        {   
            M[0] = (i - Nxc);
            M[1] = (j - Nyc);
            M[2] = Nz;
            world2cam(m, M, ocam_model);
            lineT[j].x  = (float) m[1];
            lineT[j].y  = (float) m[0];
        }
    }
}
struct ocam_model
{
        double pol[MAX_POL_LENGTH];    // the polynomial coefficients: pol[0] + x"pol[1] + x^2*pol[2] + ... + x^(N-1)*pol[N-1]
        int length_pol;                // length of polynomial
        double invpol[MAX_POL_LENGTH]; // the coefficients of the inverse polynomial
        int length_invpol;             // length of inverse polynomial
        double xc;         // row coordinate of the center
        double yc;         // column coordinate of the center
        double c;          // affine parameter
        double d;          // affine parameter
        double e;          // affine parameter
        int width;         // image width
        int height;        // image height
};
void world2cam(double point2D[2], double point3D[3], struct ocam_model *myocam_model)
{
   double *invpol     = myocam_model->invpol; 
   double xc          = (myocam_model->xc);
   double yc          = (myocam_model->yc); 
   double c           = (myocam_model->c);
   double d           = (myocam_model->d);
   double e           = (myocam_model->e);
   int width          = (myocam_model->width);
   int height         = (myocam_model->height);
   int length_invpol  = (myocam_model->length_invpol);
   double norm        = sqrt(point3D[0]*point3D[0] + point3D[1]*point3D[1]);
   double theta       = atan(point3D[2]/norm);
   double t, t_i;
   double rho, x, y;
   double invnorm;
   int i;
   if (norm != 0) 
   {
        invnorm = 1/norm;
        t  = theta;
        rho = invpol[0];
        t_i = 1; 
        for (i = 1; i < length_invpol; i++)
        {
            t_i *= t;
            rho += t_i*invpol[i];
        }
        x = point3D[0]*invnorm*rho;
        y = point3D[1]*invnorm*rho;      
        point2D[0] = x*c + y*d + xc;
        point2D[1] = x*e + y   + yc;
   }
    else
    {
        point2D[0] = xc;
        point2D[1] = yc;
    }
}

use "calc_undistortion_table" to replace "calc_hor_flip_table",but got wrong result. I may have created the wrong map table,some advice? Thanks

[Adarine99]

Hi Everyone: Some advice? grateful！

[zongwave]

Please read this page how to use OCamCalib camera calibration toolbox https://sites.google.com/site/scarabotix/ocamcalib-omnidirectional-camera-calibration-toolbox-for-matlab

[Adarine99]

Hi, Sorry to bother you,but want to know whether there is a difference between the function "remap" in opencv and "GLGeoMapHandler::remap" in this project.Thank you so much!

[zongwave]

Hi, Sorry to bother you,but want to know whether there is a difference between the function "remap" in opencv and "GLGeoMapHandler::remap" in this project.Thank you so much!

function "GLGeoMapHandler::remap" apply geometrical transformation to input image by GLES shader program. the map table is set by function GLGeoMapHandler::set_lut_buf https://github.com/intel/libxcam/blob/master/modules/gles/gl_geomap_handler.cpp#L760

opencv remap function is similar, here's the definition https://docs.opencv.org/3.4/da/d54/group__imgproc__transform.html#gab75ef31ce5cdfb5c44b6da5f3b908ea4