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| author | Even Rouault <even.rouault@spatialys.com> | 2020-05-12 22:01:25 +0200 |
|---|---|---|
| committer | Even Rouault <even.rouault@spatialys.com> | 2020-05-16 17:52:48 +0200 |
| commit | be6b6d7ec9de452904aaf3a2e2758197065502fd (patch) | |
| tree | c2c70496b80990e05881380c744f4304a7581837 /src/grids.cpp | |
| parent | c4059040012a9ab99831c2e0dec7b961fbf7cd5e (diff) | |
| download | PROJ-be6b6d7ec9de452904aaf3a2e2758197065502fd.tar.gz PROJ-be6b6d7ec9de452904aaf3a2e2758197065502fd.zip | |
pj_bilinear_interpolation_three_samples(): add comments
Diffstat (limited to 'src/grids.cpp')
| -rw-r--r-- | src/grids.cpp | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/src/grids.cpp b/src/grids.cpp index a5d9da8e..3284bf02 100644 --- a/src/grids.cpp +++ b/src/grids.cpp @@ -3381,7 +3381,12 @@ bool pj_bilinear_interpolation_three_samples( return false; } + // From a input location lp, determine the grid cell into which it falls, + // by identifying the lower-left x,y of it (ix, iy), and the upper-right + // (ix2, iy2) + double grid_x = (lp.lam - extent.west) / extent.resX; + // Special case for grids with world extent, and dealing with wrap-around if (lp.lam < extent.west) { grid_x = (lp.lam + 2 * M_PI - extent.west) / extent.resX; } else if (lp.lam > extent.east) { @@ -3417,6 +3422,7 @@ bool pj_bilinear_interpolation_three_samples( return false; } + // Bilinear interpolation double frct_lam = grid_x - ix; double frct_phi = grid_y - iy; double m10 = frct_lam; |