void idct(int colors[8][8], const double data[8][8])
{
int u,v,x,y;
/* iDCT */
for (y=0; y<8; y++) {
for (x=0; x<8; x++)
{
double z = 0.0;
for (v=0; v<8; v++)
for (u=0; u<8; u++)
{
double S, q;
double Cu, Cv;
COEFFS(Cu,Cv,u,v);
S = data[v][u];
q = Cu * Cv * S *
cos((double)(2*x+1) * (double)u * PI/16.0) *
cos((double)(2*y+1) * (double)v * PI/16.0);
z += q;
}
z /= 4.0;
if (z > 255.0) z = 255.0;
if (z < 0) z = 0.0;
colors[x][y] = (unsigned char) z;
}
}
}
void idct(tga_image *tga, double data[8][8], const int xpos, const int ypos)
{
int u,v,x,y;
/* iDCT */
for (y=0; y<8; y++)
for (x=0; x<8; x++)
{
double z = 0.0;
for (v=0; v<8; v++)
for (u=0; u<8; u++)
{
double S, q;
double Cu, Cv;
COEFFS(Cu,Cv,u,v);
S = data[v][u];
q = Cu * Cv * S *
cos((double)(2*x+1) * (double)u * PI/16.0) *
cos((double)(2*y+1) * (double)v * PI/16.0);
z += q;
}
z /= 4.0;
if (z > 255.0) z = 255.0;
if (z < 0) z = 0.0;
pixel(tga, x+xpos, y+ypos) = (uint8_t) z;
}
}
arma::mat compute_dct(arma::mat& inp) {
arma::mat out(8,8);
for(int v = 0; v < 8; v++) {
for(int u = 0; u < 8; u++) {
double Cu, Cv, z = 0.0;
COEFFS(Cu,Cv,u,v);
for(int y = 0; y < 8; y++) {
for(int x = 0; x < 8; x++) {
double s, q;
s = inp.at(x,y);
q = s * cos((double)(2*x+1) * (double)u * M_PI/16.0) *
cos((double)(2*y+1) * (double)v * M_PI/16.0);
z += q;
}}
out.at(u,v) = 0.25 * Cu * Cv * z;
}}
return out;
}
