[FFmpeg-devel] [PATCH 4/4] avfilter/vf_v360: refactor (i)flat_range for fisheye

[Daniel Playfair Cal]

This changes the iflat_range and flat_range values for the fisheye
projection to match their meaning for the flat/rectilinear projection.
That is, the range is between the two x or two y coordinates of the
outermost points above/below or left/right of the center, in the
flat/rectilinear projection.

Signed-off-by: Daniel Playfair Cal <daniel.playfair.cal at gmail.com>
---
 libavfilter/vf_v360.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/libavfilter/vf_v360.c b/libavfilter/vf_v360.c
index 68bb2f7b0f..3158451963 100644
--- a/libavfilter/vf_v360.c
+++ b/libavfilter/vf_v360.c
@@ -2807,9 +2807,8 @@ static int prepare_fisheye_out(AVFilterContext *ctx)
 {
     V360Context *s = ctx->priv;
 
-    s->flat_range[0] = s->h_fov / 180.f;
-    s->flat_range[1] = s->v_fov / 180.f;
-
+    s->flat_range[0] = 0.5f * s->h_fov * M_PI / 180.f;
+    s->flat_range[1] = 0.5f * s->v_fov * M_PI / 180.f;
     return 0;
 }
 
@@ -2827,8 +2826,8 @@ static int fisheye_to_xyz(const V360Context *s,
                           int i, int j, int width, int height,
                           float *vec)
 {
-    const float uf = s->flat_range[0] * ((2.f * i) / width  - 1.f);
-    const float vf = s->flat_range[1] * ((2.f * j + 1.f) / height - 1.f);
+    const float uf = 2.f * s->flat_range[0] / M_PI * ((2.f * i) / width  - 1.f);
+    const float vf = 2.f * s->flat_range[1] / M_PI * ((2.f * j + 1.f) / height - 1.f);
 
     const float phi   = atan2f(vf, uf);
     const float theta = M_PI_2 * (1.f - hypotf(uf, vf));
@@ -2858,8 +2857,8 @@ static int prepare_fisheye_in(AVFilterContext *ctx)
 {
     V360Context *s = ctx->priv;
 
-    s->iflat_range[0] = s->ih_fov / 180.f;
-    s->iflat_range[1] = s->iv_fov / 180.f;
+    s->iflat_range[0] = 0.5f * s->ih_fov * M_PI / 180.f;
+    s->iflat_range[1] = 0.5f * s->iv_fov * M_PI / 180.f;
 
     return 0;
 }
@@ -2882,10 +2881,10 @@ static int xyz_to_fisheye(const V360Context *s,
 {
     const float h   = hypotf(vec[0], vec[1]);
     const float lh  = h > 0.f ? h : 1.f;
-    const float phi = atan2f(h, vec[2]) / M_PI;
+    const float phi = atan2f(h, vec[2]);
 
-    float uf = vec[0] / lh * phi / s->iflat_range[0];
-    float vf = vec[1] / lh * phi / s->iflat_range[1];
+    float uf = 0.5f * vec[0] / lh * phi / s->iflat_range[0];
+    float vf = 0.5f * vec[1] / lh * phi / s->iflat_range[1];
 
     const int visible = -0.5f < uf && uf < 0.5f && -0.5f < vf && vf < 0.5f;
     int ui, vi;
-- 
2.31.0