avfilter/palettegen: move box stats computation to a dedicated function

libavfilter/vf_palettegen.c

@@ -40,6 +40,8 @@ struct color_ref {
 /* Store a range of colors */
 struct range_box {
     uint32_t color;     // average color
+    int major_axis;     // best axis candidate for cutting the box
+    uint64_t weight;    // sum of all the weights of the colors
     int64_t variance;   // overall variance of the box (how much the colors are spread)
     int start;          // index in PaletteGenContext->refs
     int len;            // number of referenced colors
@@ -143,6 +145,35 @@ static av_always_inline int diff(const uint32_t a, const uint32_t b)
     return dr*dr + dg*dg + db*db;
 }
 
+static void compute_box_stats(PaletteGenContext *s, struct range_box *box)
+{
+    int rr, gr, br;
+
+    /* compute the box weight (sum all the weights of the colors in the
+     * range) and its boundings */
+    uint8_t min[3] = {0xff, 0xff, 0xff};
+    uint8_t max[3] = {0x00, 0x00, 0x00};
+    box->weight = 0;
+    for (int i = box->start; i < box->start + box->len; i++) {
+        const struct color_ref *ref = s->refs[i];
+        const uint32_t rgb = ref->color;
+        const uint8_t r = rgb >> 16 & 0xff, g = rgb >> 8 & 0xff, b = rgb & 0xff;
+        min[0] = FFMIN(r, min[0]), max[0] = FFMAX(r, max[0]);
+        min[1] = FFMIN(g, min[1]), max[1] = FFMAX(g, max[1]);
+        min[2] = FFMIN(b, min[2]), max[2] = FFMAX(b, max[2]);
+        box->weight += ref->count;
+    }
+
+    /* define the axis to sort by according to the widest range of colors */
+    rr = max[0] - min[0];
+    gr = max[1] - min[1];
+    br = max[2] - min[2];
+    box->major_axis = 1; // pick green by default (the color the eye is the most sensitive to)
+    if (br >= rr && br >= gr) box->major_axis = 2;
+    if (rr >= gr && rr >= br) box->major_axis = 0;
+    if (gr >= rr && gr >= br) box->major_axis = 1; // prefer green again
+}
+
 /**
  * Find the next box to split: pick the one with the highest variance
  */
@@ -324,35 +355,16 @@ static AVFrame *get_palette_frame(AVFilterContext *ctx)
     s->nb_boxes = 1;
 
     while (box && box->len > 1) {
-        int i, rr, gr, br, longest;
-        uint64_t median, box_weight = 0;
-
-        /* compute the box weight (sum all the weights of the colors in the
-         * range) and its boundings */
-        uint8_t min[3] = {0xff, 0xff, 0xff};
-        uint8_t max[3] = {0x00, 0x00, 0x00};
-        for (i = box->start; i < box->start + box->len; i++) {
-            const struct color_ref *ref = s->refs[i];
-            const uint32_t rgb = ref->color;
-            const uint8_t r = rgb >> 16 & 0xff, g = rgb >> 8 & 0xff, b = rgb & 0xff;
-            min[0] = FFMIN(r, min[0]), max[0] = FFMAX(r, max[0]);
-            min[1] = FFMIN(g, min[1]), max[1] = FFMAX(g, max[1]);
-            min[2] = FFMIN(b, min[2]), max[2] = FFMAX(b, max[2]);
-            box_weight += ref->count;
-        }
+        int i, longest;
+        uint64_t median, box_weight;
 
-        /* define the axis to sort by according to the widest range of colors */
-        rr = max[0] - min[0];
-        gr = max[1] - min[1];
-        br = max[2] - min[2];
-        longest = 1; // pick green by default (the color the eye is the most sensitive to)
-        if (br >= rr && br >= gr) longest = 2;
-        if (rr >= gr && rr >= br) longest = 0;
-        if (gr >= rr && gr >= br) longest = 1; // prefer green again
+        compute_box_stats(s, box);
+        longest = box->major_axis;
+        box_weight = box->weight;
 
-        ff_dlog(ctx, "box #%02X [%6d..%-6d] (%6d) w:%-6"PRIu64" ranges:[%2x %2x %2x] sort by %c (already sorted:%c) ",
+        ff_dlog(ctx, "box #%02X [%6d..%-6d] (%6d) w:%-6"PRIu64" sort by %c (already sorted:%c) ",
                 box_id, box->start, box->start + box->len - 1, box->len, box_weight,
-                rr, gr, br, "rgb"[longest], box->sorted_by == longest ? 'y':'n');
+                "rgb"[longest], box->sorted_by == longest ? 'y':'n');
 
         /* sort the range by its longest axis if it's not already sorted */
         if (box->sorted_by != longest) {