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avfilter/vf_v360: extend stereographic projection

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Add option to change central point projection.
This commit is contained in:
Paul B Mahol 2019-09-09 14:01:23 +02:00
parent 7985430c70
commit 976617c7d2
3 changed files with 30 additions and 8 deletions
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7
doc/filters.texi
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@ -18038,7 +18038,12 @@ Stereographic format. @i{(output only)}
Format specific options:
@table @option
@item h_fov
Set field of view. Values in degrees.
@item v_fov
Set horizontal/vertical field of view. Values in degrees.
@item p_lon
@item p_lat
Set central point of projection longitude/latitude. Values in degrees.
@end table
@end table

1
libavfilter/v360.h
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@ -105,6 +105,7 @@ typedef struct V360Context {
float h_fov, v_fov;
float flat_range[3];
float p_lon, p_lat;
float input_mirror_modifier[2];

30
libavfilter/vf_v360.c
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@ -33,6 +33,8 @@
* 5) Remap input frame to output frame using precalculated data
*/
#include <float.h>
#include "libavutil/avassert.h"
#include "libavutil/imgutils.h"
#include "libavutil/pixdesc.h"
@ -105,6 +107,8 @@ static const AVOption v360_options[] = {
{ "iv_flip", "flip in video vertically", OFFSET(iv_flip), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS, "iv_flip"},
{ "in_trans", "transpose video input", OFFSET(in_transpose), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS, "in_transpose"},
{ "out_trans", "transpose video output", OFFSET(out_transpose), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS, "out_transpose"},
{ "p_lon", "central projection longitude", OFFSET(p_lon), AV_OPT_TYPE_FLOAT, {.dbl=0.f}, -180.f, 180.f, FLAGS, "p_lon"},
{ "p_lat", "central projection latitude", OFFSET(p_lat), AV_OPT_TYPE_FLOAT, {.dbl=90.f}, -90.f, 90.f, FLAGS, "p_lat"},
{ NULL }
};
@ -1406,14 +1410,26 @@ static void stereographic_to_xyz(const V360Context *s,
int i, int j, int width, int height,
float *vec)
{
const float z = 0.5f * s->h_fov * M_PI / 180.f;
const float x = z * (2.f * i / width - 1.f);
const float y = z * (2.f * j / height - 1.f);
const float xy = x * x + y * y;
const float x = ((2.f * i) / width - 1.f) * (s->h_fov / 180.f) * M_PI;
const float y = ((2.f * j) / height - 1.f) * (s->v_fov / 90.f) * M_PI_2;
const float rho = hypotf(x, y) + FLT_EPSILON;
const float c = 2.f * atan2f(rho, 0.15f / 2.f);
const float cos_c = cosf(c);
const float sin_c = sinf(c);
const float cp_x = s->p_lon / 180.f * M_PI;
const float cp_y = s->p_lat / 90.f * M_PI_2;
vec[0] = 2.f * x / (1.f + xy);
vec[1] = (-1.f + xy) / (1.f + xy);
vec[2] = 2.f * y / (1.f + xy);
const float phi = cp_x + atan2f(x * sin_c, rho * cosf(cp_y) * cos_c - y * sinf(cp_y) * sin_c);
const float theta = asinf(cos_c * sinf(cp_y) + (y * sin_c * cosf(cp_y)) / rho);
const float sin_phi = sinf(phi);
const float cos_phi = cosf(phi);
const float sin_theta = sinf(theta);
const float cos_theta = cosf(theta);
vec[0] = cos_theta * sin_phi;
vec[1] = -sin_theta;
vec[2] = -cos_theta * cos_phi;
normalize_vector(vec);
}