motion estimation and compensation for very low bitrate video coding

202 Chapter D. Complements to Chapter 5
}
reference_triangle(VertOrigin, HoriOrigin, wF, Top1V,Top1H,
Top2V,Top2H,Top3V,Top3H);
/* Compute the invariants p and q of the related affine
transform */
Heigh_12 = Top2V - Top1V;
Width_12 = Top2H - Top1H;
Height_13 = Top3V - Top1V;
Width_13 = Top3H - Top1H;
denominator = Height_12 * Width_13 - Width_12 * Height_13;
p = Height_13*(Top1H-HoriOrigin)+Width_13*(VertOrigin-Top1V);
q = Height_12*(HoriOrigin-Top1H)+Width_12*(Top1V-VertOrigin);
p /= denominator;
q /= denominator;
/* Insert the equation in the system */
// vertical component of the vector
A[i*2+1][indice_of_top1]= (double)1-p-q;
A[i*2+1][indice_of_top2]= p;
A[i*2+1][indice_of_top3]= q;
// horizontal component of the vector
A[i*2+1+1][indice_of_top1]= (double)1-p-q;
A[i*2+1+1][indice_of_top2]= p;
A[i*2+1+1][indice_of_top3]= q;
// independent term
b[i*2+1] = -vertical_component(mField, i);
b[i*2+1+1] = -horizontal_component(mField, i);
}