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avfilter/vf_v360: add hammer projection

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This commit is contained in:
Paul B Mahol 2019-09-21 15:29:18 +02:00
parent 76f861bbb7
commit b8dfc108a2
3 changed files with 95 additions and 0 deletions
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3
doc/filters.texi
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@ -18063,6 +18063,9 @@ Mercator format.
@item ball
Ball format, gives significant distortion toward the back.
@item hammer
Hammer-Aitoff map projection format.
@end table
@item interp

1
libavfilter/v360.h
View File

@ -41,6 +41,7 @@ enum Projections {
STEREOGRAPHIC,
MERCATOR,
BALL,
HAMMER,
NB_PROJECTIONS,
};

91
libavfilter/vf_v360.c
View File

@ -67,6 +67,7 @@ static const AVOption v360_options[] = {
{ "sg", "stereographic", 0, AV_OPT_TYPE_CONST, {.i64=STEREOGRAPHIC}, 0, 0, FLAGS, "in" },
{ "mercator", "mercator", 0, AV_OPT_TYPE_CONST, {.i64=MERCATOR}, 0, 0, FLAGS, "in" },
{ "ball", "ball", 0, AV_OPT_TYPE_CONST, {.i64=BALL}, 0, 0, FLAGS, "in" },
{ "hammer", "hammer", 0, AV_OPT_TYPE_CONST, {.i64=HAMMER}, 0, 0, FLAGS, "in" },
{ "output", "set output projection", OFFSET(out), AV_OPT_TYPE_INT, {.i64=CUBEMAP_3_2}, 0, NB_PROJECTIONS-1, FLAGS, "out" },
{ "e", "equirectangular", 0, AV_OPT_TYPE_CONST, {.i64=EQUIRECTANGULAR}, 0, 0, FLAGS, "out" },
{ "equirect", "equirectangular", 0, AV_OPT_TYPE_CONST, {.i64=EQUIRECTANGULAR}, 0, 0, FLAGS, "out" },
@ -83,6 +84,7 @@ static const AVOption v360_options[] = {
{ "sg", "stereographic", 0, AV_OPT_TYPE_CONST, {.i64=STEREOGRAPHIC}, 0, 0, FLAGS, "out" },
{ "mercator", "mercator", 0, AV_OPT_TYPE_CONST, {.i64=MERCATOR}, 0, 0, FLAGS, "out" },
{ "ball", "ball", 0, AV_OPT_TYPE_CONST, {.i64=BALL}, 0, 0, FLAGS, "out" },
{ "hammer", "hammer", 0, AV_OPT_TYPE_CONST, {.i64=HAMMER}, 0, 0, FLAGS, "out" },
{ "interp", "set interpolation method", OFFSET(interp), AV_OPT_TYPE_INT, {.i64=BILINEAR}, 0, NB_INTERP_METHODS-1, FLAGS, "interp" },
{ "near", "nearest neighbour", 0, AV_OPT_TYPE_CONST, {.i64=NEAREST}, 0, 0, FLAGS, "interp" },
{ "nearest", "nearest neighbour", 0, AV_OPT_TYPE_CONST, {.i64=NEAREST}, 0, 0, FLAGS, "interp" },
@ -1658,6 +1660,83 @@ static void ball_to_xyz(const V360Context *s,
}
}
/**
* Calculate 3D coordinates on sphere for corresponding frame position in hammer format.
*
* @param s filter private context
* @param i horizontal position on frame [0, width)
* @param j vertical position on frame [0, height)
* @param width frame width
* @param height frame height
* @param vec coordinates on sphere
*/
static void hammer_to_xyz(const V360Context *s,
int i, int j, int width, int height,
float *vec)
{
const float x = ((2.f * i) / width - 1.f);
const float y = ((2.f * j) / height - 1.f);
const float xx = x * x;
const float yy = y * y;
const float z = sqrtf(1.f - xx * 0.5f - yy * 0.5f);
const float a = M_SQRT2 * x * z;
const float b = 2.f * z * z - 1.f;
const float aa = a * a;
const float bb = b * b;
const float w = sqrtf(1.f - 2.f * yy * z * z);
vec[0] = w * 2.f * a * b / (aa + bb);
vec[1] = -M_SQRT2 * y * z;
vec[2] = -w * (bb - aa) / (aa + bb);
normalize_vector(vec);
}
/**
* Calculate frame position in hammer format for corresponding 3D coordinates on sphere.
*
* @param s filter private context
* @param vec coordinates on sphere
* @param width frame width
* @param height frame height
* @param us horizontal coordinates for interpolation window
* @param vs vertical coordinates for interpolation window
* @param du horizontal relative coordinate
* @param dv vertical relative coordinate
*/
static void xyz_to_hammer(const V360Context *s,
const float *vec, int width, int height,
uint16_t us[4][4], uint16_t vs[4][4], float *du, float *dv)
{
const float theta = atan2f(vec[0], -vec[2]) * s->input_mirror_modifier[0];
const float z = sqrtf(1.f + sqrtf(1.f - vec[1] * vec[1]) * cosf(theta * 0.5f));
const float x = sqrtf(1.f - vec[1] * vec[1]) * sinf(theta * 0.5f) / z;
const float y = -vec[1] / z * s->input_mirror_modifier[1];
float uf, vf;
int ui, vi;
uf = (x + 1.f) * width / 2.f;
vf = (y + 1.f) * height / 2.f;
ui = floorf(uf);
vi = floorf(vf);
*du = uf - ui;
*dv = vf - vi;
for (int i = -1; i < 3; i++) {
for (int j = -1; j < 3; j++) {
us[i + 1][j + 1] = mod(ui + j, width);
vs[i + 1][j + 1] = av_clip(vi + i, 0, height - 1);
}
}
}
/**
* Prepare data for processing equi-angular cubemap input format.
*
@ -2512,6 +2591,12 @@ static int config_output(AVFilterLink *outlink)
wf = w;
hf = h / 2.f;
break;
case HAMMER:
s->in_transform = xyz_to_hammer;
err = 0;
wf = w;
hf = h;
break;
default:
av_log(ctx, AV_LOG_ERROR, "Specified input format is not handled.\n");
return AVERROR_BUG;
@ -2588,6 +2673,12 @@ static int config_output(AVFilterLink *outlink)
w = roundf(wf);
h = roundf(hf * 2.f);
break;
case HAMMER:
s->out_transform = hammer_to_xyz;
prepare_out = NULL;
w = roundf(wf);
h = roundf(hf);
break;
default:
av_log(ctx, AV_LOG_ERROR, "Specified output format is not handled.\n");
return AVERROR_BUG;