| 1411 | coeffs[3] = 1.f - coeffs[0] - coeffs[1] - coeffs[2]; |
| 1412 | } |
| 1413 | static inline void interpolate_lanczos4(float x, float* coeffs) { |
| 1414 | static const double s45 = 0.70710678118654752440084436210485; |
| 1415 | static const double cs[][2] = {{1, 0}, {-s45, -s45}, {0, 1}, {s45, -s45}, |
| 1416 | {-1, 0}, {s45, s45}, {0, -1}, {-s45, s45}}; |
| 1417 | |
| 1418 | if (x < FLT_EPSILON) { |
| 1419 | for (int i = 0; i < 8; i++) |
| 1420 | coeffs[i] = 0; |
| 1421 | coeffs[3] = 1; |
| 1422 | return; |
| 1423 | } |
| 1424 | |
| 1425 | float sum = 0; |
| 1426 | double y0 = -(x + 3) * MEGCV_PI * 0.25, s0 = sin(y0), c0 = cos(y0); |
| 1427 | for (int i = 0; i < 8; i++) { |
| 1428 | double y = -(x + 3 - i) * MEGCV_PI * 0.25; |
| 1429 | coeffs[i] = (float)((cs[i][0] * s0 + cs[i][1] * c0) / (y * y)); |
| 1430 | sum += coeffs[i]; |
| 1431 | } |
| 1432 | |
| 1433 | sum = 1.f / sum; |
| 1434 | for (int i = 0; i < 8; i++) |
| 1435 | coeffs[i] *= sum; |
| 1436 | } |
| 1437 | |
| 1438 | template <typename T, typename WT, typename AT> |
| 1439 | struct HResizeLanczos4 { |
no test coverage detected