avfilter/vf_vectorscope: always flip output vertically

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/vf_vectorscope.c

@@ -911,7 +911,7 @@ static void draw_htext(AVFrame *out, int x, int y, float o1, float o2, const cha
             int v = color[plane];
 
             uint8_t *p = out->data[plane] + y * out->linesize[plane] + (x + i * 8);
-            for (char_y = 0; char_y < font_height; char_y++) {
+            for (char_y = font_height - 1; char_y >= 0; char_y--) {
                 for (mask = 0x80; mask; mask >>= 1) {
                     if (font[txt[i] * font_height + char_y] & mask)
                         p[0] = p[0] * o2 + v * o1;
@@ -937,7 +937,7 @@ static void draw_htext16(AVFrame *out, int x, int y, float o1, float o2, const c
             int v = color[plane];
 
             uint16_t *p = (uint16_t *)(out->data[plane] + y * out->linesize[plane]) + (x + i * 8);
-            for (char_y = 0; char_y < font_height; char_y++) {
+            for (char_y = font_height - 1; char_y >= 0; char_y--) {
                 for (mask = 0x80; mask; mask >>= 1) {
                     if (font[txt[i] * font_height + char_y] & mask)
                         p[0] = p[0] * o2 + v * o1;
@@ -1207,6 +1207,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
     VectorscopeContext *s = ctx->priv;
     AVFilterLink *outlink = ctx->outputs[0];
     AVFrame *out;
+    int plane;
 
     if (s->colorspace) {
         s->cs = (s->depth - 8) * 2 + s->colorspace - 1;
@@ -1232,6 +1233,13 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
     s->vectorscope(s, in, out, s->pd);
     s->graticulef(s, out, s->x, s->y, s->pd, s->cs);
 
+    for (plane = 0; plane < 4; plane++) {
+        if (out->data[plane]) {
+            out->data[plane]    += (s->size - 1) * out->linesize[plane];
+            out->linesize[plane] = -out->linesize[plane];
+        }
+    }
+
     av_frame_free(&in);
     return ff_filter_frame(outlink, out);
 }

tests/ref/fate/filter-vectorscope_color

 #tb 0: 1/25
-0,          0,          0,        1,   196608, 0x1890aa30
-0,          1,          1,        1,   196608, 0xa490acf9
-0,          2,          2,        1,   196608, 0x404a775d
+0,          0,          0,        1,   196608, 0xf6e3aa30
+0,          1,          1,        1,   196608, 0x5584acf9
+0,          2,          2,        1,   196608, 0xa862775d

tests/ref/fate/filter-vectorscope_color2

 #tb 0: 1/25
-0,          0,          0,        1,   196608, 0x9bfcfae5
-0,          1,          1,        1,   196608, 0x1ac6fcbf
-0,          2,          2,        1,   196608, 0x31cb1088
+0,          0,          0,        1,   196608, 0x5e62fae5
+0,          1,          1,        1,   196608, 0x4c27fcbf
+0,          2,          2,        1,   196608, 0xb7531088

tests/ref/fate/filter-vectorscope_color3

 #tb 0: 1/25
-0,          0,          0,        1,   196608, 0x6e698770
-0,          1,          1,        1,   196608, 0x374d74a7
-0,          2,          2,        1,   196608, 0x3d817143
+0,          0,          0,        1,   196608, 0x83df8770
+0,          1,          1,        1,   196608, 0xa6a674a7
+0,          2,          2,        1,   196608, 0x11757143

tests/ref/fate/filter-vectorscope_color4

 #tb 0: 1/25
-0,          0,          0,        1,   196608, 0x4d2e53c4
-0,          1,          1,        1,   196608, 0x795e1dcc
-0,          2,          2,        1,   196608, 0xe4268800
+0,          0,          0,        1,   196608, 0x326953c4
+0,          1,          1,        1,   196608, 0x870e1dcc
+0,          2,          2,        1,   196608, 0x87cb8800

tests/ref/fate/filter-vectorscope_gray

 #tb 0: 1/25
-0,          0,          0,        1,   196608, 0x8e4171e2
-0,          1,          1,        1,   196608, 0xf3d371e2
-0,          2,          2,        1,   196608, 0xb9cb71e2
+0,          0,          0,        1,   196608, 0x79ba71e2
+0,          1,          1,        1,   196608, 0x909271e2
+0,          2,          2,        1,   196608, 0x143971e2

tests/ref/fate/filter-vectorscope_xy

 #tb 0: 1/25
-0,          0,          0,        1,   196608, 0xa0939af1
-0,          1,          1,        1,   196608, 0x43699af1
-0,          2,          2,        1,   196608, 0x69a19af1
+0,          0,          0,        1,   196608, 0xa2899af1
+0,          1,          1,        1,   196608, 0x26409af1
+0,          2,          2,        1,   196608, 0xf5209af1