[FFmpeg-devel] [PATCH] libavfi: added option to vf_perspective to specify transformation by giving destinations of corners of source.
Nicholas Robbins
nickrobbins at yahoo.com
Sun Oct 19 15:20:22 CEST 2014
Signed-off-by: Nicholas Robbins <nickrobbins at yahoo.com>
---
doc/filters.texi | 21 +++++++++++
libavfilter/vf_perspective.c | 85 +++++++++++++++++++++++++++++++++-----------
2 files changed, 86 insertions(+), 20 deletions(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index b847635..c612052 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -6718,6 +6718,9 @@ A description of the accepted parameters follows.
@item y3
Set coordinates expression for top left, top right, bottom left and bottom right corners.
Default values are @code{0:0:W:0:0:H:W:H} with which perspective will remain unchanged.
+If the @code{sense} option is set to @code{source}, then the specified points will be sent
+to the corners of the destination. If the @code{sense} option is set to @code{destination},
+then the corners of the source will be sent to the specified coordinates.
The expressions can use the following variables:
@@ -6737,6 +6740,24 @@ It accepts the following values:
@end table
Default value is @samp{linear}.
+
+ at item sense
+Set interpretation of coordinate options.
+
+It accepts the following values:
+ at table @samp
+ at item 0, source
+
+Send point in the source specified by the given coordinates to
+the corners of the destination.
+
+ at item 1, destination
+
+Send the corners of the source to the point in the destination specified
+by the given coordinates.
+
+Default value is @samp{source}.
+ at end table
@end table
@section phase
diff --git a/libavfilter/vf_perspective.c b/libavfilter/vf_perspective.c
index a796bd4..bf06d02 100644
--- a/libavfilter/vf_perspective.c
+++ b/libavfilter/vf_perspective.c
@@ -46,6 +46,7 @@ typedef struct PerspectiveContext {
int height[4];
int hsub, vsub;
int nb_planes;
+ int sense;
int (*perspective)(AVFilterContext *ctx,
void *arg, int job, int nb_jobs);
@@ -54,6 +55,11 @@ typedef struct PerspectiveContext {
#define OFFSET(x) offsetof(PerspectiveContext, x)
#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+enum PERSPECTIVESense {
+ PERSPECTIVE_SENSE_SOURCE = 0, ///< coordinates give locations in source of corners of destination.
+ PERSPECTIVE_SENSE_DESTINATION = 1, ///< coordinates give locations in destination of corners of source.
+};
+
static const AVOption perspective_options[] = {
{ "x0", "set top left x coordinate", OFFSET(expr_str[0][0]), AV_OPT_TYPE_STRING, {.str="0"}, 0, 0, FLAGS },
{ "y0", "set top left y coordinate", OFFSET(expr_str[0][1]), AV_OPT_TYPE_STRING, {.str="0"}, 0, 0, FLAGS },
@@ -66,6 +72,12 @@ static const AVOption perspective_options[] = {
{ "interpolation", "set interpolation", OFFSET(interpolation), AV_OPT_TYPE_INT, {.i64=LINEAR}, 0, 1, FLAGS, "interpolation" },
{ "linear", "", 0, AV_OPT_TYPE_CONST, {.i64=LINEAR}, 0, 0, FLAGS, "interpolation" },
{ "cubic", "", 0, AV_OPT_TYPE_CONST, {.i64=CUBIC}, 0, 0, FLAGS, "interpolation" },
+ { "sense", "specify the sense of the coordinates", OFFSET(sense), AV_OPT_TYPE_INT, {.i64=PERSPECTIVE_SENSE_SOURCE}, 0, 1, FLAGS, "sense"},
+ { "source", "specify locations in source to send to corners in destination",
+ 0, AV_OPT_TYPE_CONST, {.i64=PERSPECTIVE_SENSE_SOURCE}, 0, 0, FLAGS, "sense"},
+ { "destination", "specify locations in destination to send corners of source",
+ 0, AV_OPT_TYPE_CONST, {.i64=PERSPECTIVE_SENSE_DESTINATION}, 0, 0, FLAGS, "sense"},
+
{ NULL }
};
@@ -105,7 +117,8 @@ enum { VAR_W, VAR_H, VAR_VARS_NB };
static int config_input(AVFilterLink *inlink)
{
- double x0, x1, x2, x3, x4, x5, x6, x7, q;
+ double x0, x1, x2, x3, x4, x5, x6, x7, x8, q;
+ double t0, t1, t2, t3;
AVFilterContext *ctx = inlink->dst;
PerspectiveContext *s = ctx->priv;
double (*ref)[2] = s->ref;
@@ -141,32 +154,64 @@ static int config_input(AVFilterLink *inlink)
if (!s->pv)
return AVERROR(ENOMEM);
- x6 = ((ref[0][0] - ref[1][0] - ref[2][0] + ref[3][0]) *
- (ref[2][1] - ref[3][1]) -
- ( ref[0][1] - ref[1][1] - ref[2][1] + ref[3][1]) *
- (ref[2][0] - ref[3][0])) * h;
- x7 = ((ref[0][1] - ref[1][1] - ref[2][1] + ref[3][1]) *
- (ref[1][0] - ref[3][0]) -
- ( ref[0][0] - ref[1][0] - ref[2][0] + ref[3][0]) *
- (ref[1][1] - ref[3][1])) * w;
- q = ( ref[1][0] - ref[3][0]) * (ref[2][1] - ref[3][1]) -
- ( ref[2][0] - ref[3][0]) * (ref[1][1] - ref[3][1]);
-
- x0 = q * (ref[1][0] - ref[0][0]) * h + x6 * ref[1][0];
- x1 = q * (ref[2][0] - ref[0][0]) * w + x7 * ref[2][0];
- x2 = q * ref[0][0] * w * h;
- x3 = q * (ref[1][1] - ref[0][1]) * h + x6 * ref[1][1];
- x4 = q * (ref[2][1] - ref[0][1]) * w + x7 * ref[2][1];
- x5 = q * ref[0][1] * w * h;
+ switch (s->sense) {
+ case PERSPECTIVE_SENSE_SOURCE:
+ x6 = ((ref[0][0] - ref[1][0] - ref[2][0] + ref[3][0]) *
+ (ref[2][1] - ref[3][1]) -
+ ( ref[0][1] - ref[1][1] - ref[2][1] + ref[3][1]) *
+ (ref[2][0] - ref[3][0])) * h;
+ x7 = ((ref[0][1] - ref[1][1] - ref[2][1] + ref[3][1]) *
+ (ref[1][0] - ref[3][0]) -
+ ( ref[0][0] - ref[1][0] - ref[2][0] + ref[3][0]) *
+ (ref[1][1] - ref[3][1])) * w;
+ q = ( ref[1][0] - ref[3][0]) * (ref[2][1] - ref[3][1]) -
+ ( ref[2][0] - ref[3][0]) * (ref[1][1] - ref[3][1]);
+
+ x0 = q * (ref[1][0] - ref[0][0]) * h + x6 * ref[1][0];
+ x1 = q * (ref[2][0] - ref[0][0]) * w + x7 * ref[2][0];
+ x2 = q * ref[0][0] * w * h;
+ x3 = q * (ref[1][1] - ref[0][1]) * h + x6 * ref[1][1];
+ x4 = q * (ref[2][1] - ref[0][1]) * w + x7 * ref[2][1];
+ x5 = q * ref[0][1] * w * h;
+ x8 = q * w * h;
+ break;
+ case PERSPECTIVE_SENSE_DESTINATION:
+ t0 = ref[0][0] * (ref[3][1] - ref[1][1]) +
+ ref[1][0] * (ref[0][1] - ref[3][1]) +
+ ref[3][0] * (ref[1][1] - ref[0][1]);
+ t1 = ref[1][0] * (ref[2][1] - ref[3][1]) +
+ ref[2][0] * (ref[3][1] - ref[1][1]) +
+ ref[3][0] * (ref[1][1] - ref[2][1]);
+ t2 = ref[0][0] * (ref[3][1] - ref[2][1]) +
+ ref[2][0] * (ref[0][1] - ref[3][1]) +
+ ref[3][0] * (ref[2][1] - ref[0][1]);
+ t3 = ref[0][0] * (ref[1][1] - ref[2][1]) +
+ ref[1][0] * (ref[2][1] - ref[0][1]) +
+ ref[2][0] * (ref[0][1] - ref[1][1]);
+
+ x0 = t0 * t1 * w * (ref[2][1] - ref[0][1]);
+ x1 = t0 * t1 * w * (ref[0][0] - ref[2][0]);
+ x2 = t0 * t1 * w * (ref[0][1] * ref[2][0] - ref[0][0] * ref[2][1]);
+ x3 = t1 * t2 * h * (ref[1][1] - ref[0][1]);
+ x4 = t1 * t2 * h * (ref[0][0] - ref[1][0]);
+ x5 = t1 * t2 * h * (ref[0][1] * ref[1][0] - ref[0][0] * ref[1][1]);
+ x6 = t1 * t2 * (ref[1][1] - ref[0][1]) +
+ t0 * t3 * (ref[2][1] - ref[3][1]);
+ x7 = t1 * t2 * (ref[0][0] - ref[1][0]) +
+ t0 * t3 * (ref[3][0] - ref[2][0]);
+ x8 = t1 * t2 * (ref[0][1] * ref[1][0] - ref[0][0] * ref[1][1]) +
+ t0 * t3 * (ref[2][0] * ref[3][1] - ref[2][1] * ref[3][0]);
+ break;
+ }
for (y = 0; y < h; y++){
for (x = 0; x < w; x++){
int u, v;
u = (int)floor(SUB_PIXELS * (x0 * x + x1 * y + x2) /
- (x6 * x + x7 * y + q * w * h) + 0.5);
+ (x6 * x + x7 * y + x8) + 0.5);
v = (int)floor(SUB_PIXELS * (x3 * x + x4 * y + x5) /
- (x6 * x + x7 * y + q * w * h) + 0.5);
+ (x6 * x + x7 * y + x8) + 0.5);
s->pv[x + y * w][0] = u;
s->pv[x + y * w][1] = v;
--
1.8.5.5
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