# LibRaw/LibRaw-demosaic-pack-GPL3

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 /* Short Discrete Cosine Transform data length :8x8 method :row-column, radix 4 FFT functions ddct8x8s : 8x8 DCT function prototypes void ddct8x8s(int isgn, float **a); */ /* -------- 8x8 DCT (Discrete Cosine Transform) / Inverse of DCT -------- [definition] Normalized 8x8 IDCT C[k1][k2] = (1/4) * sum_j1=0^7 sum_j2=0^7 a[j1][j2] * s[j1] * s[j2] * cos(pi*j1*(k1+1/2)/8) * cos(pi*j2*(k2+1/2)/8), 0<=k1<8, 0<=k2<8 (s[0] = 1/sqrt(2), s[j] = 1, j > 0) Normalized 8x8 DCT C[k1][k2] = (1/4) * s[k1] * s[k2] * sum_j1=0^7 sum_j2=0^7 a[j1][j2] * cos(pi*(j1+1/2)*k1/8) * cos(pi*(j2+1/2)*k2/8), 0<=k1<8, 0<=k2<8 (s[0] = 1/sqrt(2), s[j] = 1, j > 0) [usage] ddct8x8s(1, a); ddct8x8s(-1, a); [parameters] a[0...7][0...7] :input/output data (double **) output data a[k1][k2] = C[k1][k2], 0<=k1<8, 0<=k2<8 */ /* Cn_kR = sqrt(2.0/n) * cos(pi/2*k/n) */ /* Cn_kI = sqrt(2.0/n) * sin(pi/2*k/n) */ /* Wn_kR = cos(pi/2*k/n) */ /* Wn_kI = sin(pi/2*k/n) */ #define C8_1R 0.49039264020161522456 #define C8_1I 0.09754516100806413392 #define C8_2R 0.46193976625564337806 #define C8_2I 0.19134171618254488586 #define C8_3R 0.41573480615127261854 #define C8_3I 0.27778511650980111237 #define C8_4R 0.35355339059327376220 #define W8_4R 0.70710678118654752440 void ddct8x8s(int isgn, float **a) { int j; float x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i; float xr, xi; if (isgn < 0) { for (j = 0; j <= 7; j++) { x0r = a[0][j] + a[7][j]; x1r = a[0][j] - a[7][j]; x0i = a[2][j] + a[5][j]; x1i = a[2][j] - a[5][j]; x2r = a[4][j] + a[3][j]; x3r = a[4][j] - a[3][j]; x2i = a[6][j] + a[1][j]; x3i = a[6][j] - a[1][j]; xr = x0r + x2r; xi = x0i + x2i; a[0][j] = C8_4R * (xr + xi); a[4][j] = C8_4R * (xr - xi); xr = x0r - x2r; xi = x0i - x2i; a[2][j] = C8_2R * xr - C8_2I * xi; a[6][j] = C8_2R * xi + C8_2I * xr; xr = W8_4R * (x1i - x3i); x1i = W8_4R * (x1i + x3i); x3i = x1i - x3r; x1i += x3r; x3r = x1r - xr; x1r += xr; a[1][j] = C8_1R * x1r - C8_1I * x1i; a[7][j] = C8_1R * x1i + C8_1I * x1r; a[3][j] = C8_3R * x3r - C8_3I * x3i; a[5][j] = C8_3R * x3i + C8_3I * x3r; } for (j = 0; j <= 7; j++) { x0r = a[j][0] + a[j][7]; x1r = a[j][0] - a[j][7]; x0i = a[j][2] + a[j][5]; x1i = a[j][2] - a[j][5]; x2r = a[j][4] + a[j][3]; x3r = a[j][4] - a[j][3]; x2i = a[j][6] + a[j][1]; x3i = a[j][6] - a[j][1]; xr = x0r + x2r; xi = x0i + x2i; a[j][0] = C8_4R * (xr + xi); a[j][4] = C8_4R * (xr - xi); xr = x0r - x2r; xi = x0i - x2i; a[j][2] = C8_2R * xr - C8_2I * xi; a[j][6] = C8_2R * xi + C8_2I * xr; xr = W8_4R * (x1i - x3i); x1i = W8_4R * (x1i + x3i); x3i = x1i - x3r; x1i += x3r; x3r = x1r - xr; x1r += xr; a[j][1] = C8_1R * x1r - C8_1I * x1i; a[j][7] = C8_1R * x1i + C8_1I * x1r; a[j][3] = C8_3R * x3r - C8_3I * x3i; a[j][5] = C8_3R * x3i + C8_3I * x3r; } } else { for (j = 0; j <= 7; j++) { x1r = C8_1R * a[1][j] + C8_1I * a[7][j]; x1i = C8_1R * a[7][j] - C8_1I * a[1][j]; x3r = C8_3R * a[3][j] + C8_3I * a[5][j]; x3i = C8_3R * a[5][j] - C8_3I * a[3][j]; xr = x1r - x3r; xi = x1i + x3i; x1r += x3r; x3i -= x1i; x1i = W8_4R * (xr + xi); x3r = W8_4R * (xr - xi); xr = C8_2R * a[2][j] + C8_2I * a[6][j]; xi = C8_2R * a[6][j] - C8_2I * a[2][j]; x0r = C8_4R * (a[0][j] + a[4][j]); x0i = C8_4R * (a[0][j] - a[4][j]); x2r = x0r - xr; x2i = x0i - xi; x0r += xr; x0i += xi; a[0][j] = x0r + x1r; a[7][j] = x0r - x1r; a[2][j] = x0i + x1i; a[5][j] = x0i - x1i; a[4][j] = x2r - x3i; a[3][j] = x2r + x3i; a[6][j] = x2i - x3r; a[1][j] = x2i + x3r; } for (j = 0; j <= 7; j++) { x1r = C8_1R * a[j][1] + C8_1I * a[j][7]; x1i = C8_1R * a[j][7] - C8_1I * a[j][1]; x3r = C8_3R * a[j][3] + C8_3I * a[j][5]; x3i = C8_3R * a[j][5] - C8_3I * a[j][3]; xr = x1r - x3r; xi = x1i + x3i; x1r += x3r; x3i -= x1i; x1i = W8_4R * (xr + xi); x3r = W8_4R * (xr - xi); xr = C8_2R * a[j][2] + C8_2I * a[j][6]; xi = C8_2R * a[j][6] - C8_2I * a[j][2]; x0r = C8_4R * (a[j][0] + a[j][4]); x0i = C8_4R * (a[j][0] - a[j][4]); x2r = x0r - xr; x2i = x0i - xi; x0r += xr; x0i += xi; a[j][0] = x0r + x1r; a[j][7] = x0r - x1r; a[j][2] = x0i + x1i; a[j][5] = x0i - x1i; a[j][4] = x2r - x3i; a[j][3] = x2r + x3i; a[j][6] = x2i - x3r; a[j][1] = x2i + x3r; } } }
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