3 files changed, 48 insertions, 0 deletions

diff --git a/video/out/gl_video.c b/video/out/gl_video.c
index f1ea03ed80..7420d9d4d1 100644
--- a/video/out/gl_video.c
+++ b/video/out/gl_video.c
@@ -355,6 +355,7 @@ static int validate_scaler_opt(struct mp_log *log, const m_option_t *opt,
 const struct m_sub_options gl_video_conf = {
     .opts = (const m_option_t[]) {
         OPT_FLOATRANGE("gamma", gamma, 0, 0.1, 2.0),
+        OPT_FLAG("gamma-auto", gamma_auto, 0),
         OPT_FLAG("srgb", srgb, 0),
         OPT_FLAG("npot", npot, 0),
         OPT_FLAG("pbo", pbo, 0),
@@ -2564,6 +2565,31 @@ void gl_video_resize_redraw(struct gl_video *p, int w, int h)
     gl_video_render_frame(p, 0, NULL);
 }
 
+float gl_video_scale_ambient_lux(float lmin, float lmax,
+                                 float rmin, float rmax, float lux)
+{
+    assert(lmax > lmin);
+
+    float num = (rmax - rmin) * (log10(lux) - log10(lmin));
+    float den = log10(lmax) - log10(lmin);
+    float result = num / den + rmin;
+
+    // clamp the result
+    float max = MPMAX(rmax, rmin);
+    float min = MPMIN(rmax, rmin);
+    return MPMAX(MPMIN(result, max), min);
+}
+
+void gl_video_set_ambient_lux(struct gl_video *p, int lux)
+{
+    if (p->opts.gamma_auto) {
+        float gamma = gl_video_scale_ambient_lux(16.0, 64.0, 2.40, 1.961, lux);
+        MP_INFO(p, "ambient light changed: %dlux (gamma: %f)\n", lux, gamma);
+        p->opts.gamma = MPMIN(1.0, 1.961 / gamma);
+        gl_video_eq_update(p);
+    }
+}
+
 void gl_video_set_hwdec(struct gl_video *p, struct gl_hwdec *hwdec)
 {
     p->hwdec = hwdec;
diff --git a/video/out/gl_video.h b/video/out/gl_video.h
index 74a8b7fd93..8c273faa9e 100644
--- a/video/out/gl_video.h
+++ b/video/out/gl_video.h
@@ -35,6 +35,7 @@ struct gl_video_opts {
     float scaler_radius[2];
     float scaler_antiring[2];
     float gamma;
+    int gamma_auto;
     int srgb;
     int linear_scaling;
     int fancy_downscaling;
@@ -83,6 +84,10 @@ void gl_video_eq_update(struct gl_video *p);
 void gl_video_set_debug(struct gl_video *p, bool enable);
 void gl_video_resize_redraw(struct gl_video *p, int w, int h);
 
+float gl_video_scale_ambient_lux(float lmin, float lmax,
+                                 float rmin, float rmax, float lux);
+void gl_video_set_ambient_lux(struct gl_video *p, int lux);
+
 void gl_video_set_gl_state(struct gl_video *p);
 void gl_video_unset_gl_state(struct gl_video *p);
 void gl_video_reset(struct gl_video *p);
diff --git a/video/out/vo_opengl.c b/video/out/vo_opengl.c
index a9435eeac2..9318914dbd 100644
--- a/video/out/vo_opengl.c
+++ b/video/out/vo_opengl.c
@@ -276,6 +276,19 @@ static bool get_and_update_icc_profile(struct gl_priv *p, int *events)
     return true;
 }
 
+static void get_and_update_ambient_lighting(struct gl_priv *p, int *events)
+{
+    int lux;
+    int r = p->glctx->vo_control(p->vo, events, VOCTRL_GET_AMBIENT_LUX, &lux);
+    if (r == VO_TRUE) {
+        gl_video_set_ambient_lux(p->renderer, lux);
+    }
+    if (r != VO_TRUE && p->renderer_opts->gamma_auto) {
+        MP_ERR(p, "gamma_auto option provided, but querying for ambient"
+                  " lighting is not supported on this platform\n");
+    }
+}
+
 static bool reparse_cmdline(struct gl_priv *p, char *args)
 {
     struct m_config *cfg = NULL;
@@ -390,6 +403,10 @@ static int control(struct vo *vo, uint32_t request, void *data)
         get_and_update_icc_profile(p, &events);
         vo->want_redraw = true;
     }
+    if (events & VO_EVENT_AMBIENT_LIGHTING_CHANGED) {
+        get_and_update_ambient_lighting(p, &events);
+        vo->want_redraw = true;
+    }
     if (events & VO_EVENT_RESIZE)
         resize(p);
     if (events & VO_EVENT_EXPOSE)