avfilter/vf_pixscope: also show standard deviation of zoomed area

libavfilter/vf_datascope.c

@@ -452,6 +452,8 @@ typedef struct PixscopeContext {
     FFDrawColor   red;
     FFDrawColor  *colors[4];
 
+    uint16_t values[4][80][80];
+
     void (*pick_color)(FFDrawContext *draw, FFDrawColor *color, AVFrame *in, int x, int y, int *value);
 } PixscopeContext;
 
@@ -526,6 +528,8 @@ static int pixscope_config_input(AVFilterLink *inlink)
     return 0;
 }
 
+#define SQR(x) ((x)*(x))
+
 static int pixscope_filter_frame(AVFilterLink *inlink, AVFrame *in)
 {
     AVFilterContext *ctx  = inlink->dst;
@@ -534,7 +538,7 @@ static int pixscope_filter_frame(AVFilterLink *inlink, AVFrame *in)
     AVFrame *out = ff_get_video_buffer(outlink, in->width, in->height);
     int max[4] = { 0 }, min[4] = { INT_MAX, INT_MAX, INT_MAX, INT_MAX };
     float average[4] = { 0 };
-    double rms[4] = { 0 };
+    double std[4] = { 0 }, rms[4] = { 0 };
     const char rgba[4] = { 'R', 'G', 'B', 'A' };
     const char yuva[4] = { 'Y', 'U', 'V', 'A' };
     int x, y, X, Y, i, w, h;
@@ -591,6 +595,7 @@ static int pixscope_filter_frame(AVFilterLink *inlink, AVFrame *in)
             ff_fill_rectangle(&s->draw, &color, out->data, out->linesize,
                               x * w + (s->ww - 4 - (s->w * w)) / 2 + X, y * h + 2 + Y, w, h);
             for (i = 0; i < 4; i++) {
+                s->values[i][x][y] = value[i];
                 rms[i]     += (double)value[i] * (double)value[i];
                 average[i] += value[i];
                 min[i]      = FFMIN(min[i], value[i]);
@@ -637,13 +642,33 @@ static int pixscope_filter_frame(AVFilterLink *inlink, AVFrame *in)
         average[i] /= s->w * s->h;
     }
 
+    for (y = 0; y < s->h; y++) {
+        for (x = 0; x < s->w; x++) {
+            for (i = 0; i < 4; i++)
+                std[i] += SQR(s->values[i][x][y] - average[i]);
+        }
+    }
+
+    for (i = 0; i < 4; i++) {
+        std[i] /= s->w * s->h;
+        std[i]  = sqrt(std[i]);
+    }
+
     snprintf(text, sizeof(text), "CH   AVG    MIN    MAX    RMS\n");
-    draw_text(&s->draw, out, &s->white,        X + 28, Y + s->ww + 20,           text, 0);
+    draw_text(&s->draw, out, &s->white,        X + 28, Y + s->ww +  5,           text, 0);
     for (i = 0; i < s->nb_comps; i++) {
         int c = s->rgba_map[i];
 
         snprintf(text, sizeof(text), "%c  %07.1f %05d %05d %07.1f\n", s->is_rgb ? rgba[i] : yuva[i], average[c], min[c], max[c], rms[c]);
-        draw_text(&s->draw, out, s->colors[i], X + 28, Y + s->ww + 20 * (i + 2), text, 0);
+        draw_text(&s->draw, out, s->colors[i], X + 28, Y + s->ww + 15 * (i + 1), text, 0);
+    }
+    snprintf(text, sizeof(text), "CH   STD\n");
+    draw_text(&s->draw, out, &s->white,        X + 28, Y + s->ww + 15 * (0 + 5), text, 0);
+    for (i = 0; i < s->nb_comps; i++) {
+        int c = s->rgba_map[i];
+
+        snprintf(text, sizeof(text), "%c  %07.2f\n", s->is_rgb ? rgba[i] : yuva[i], std[c]);
+        draw_text(&s->draw, out, s->colors[i], X + 28, Y + s->ww + 15 * (i + 6), text, 0);
     }
 
     av_frame_free(&in);