avfilter/vf_hflip: refactor plane dimensions calculation

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

libavfilter/vf_hflip.c

@@ -37,7 +37,8 @@
 
 typedef struct {
     int max_step[4];    ///< max pixel step for each plane, expressed as a number of bytes
-    int hsub, vsub;     ///< chroma subsampling
+    int planewidth[4];  ///< width of each plane
+    int planeheight[4]; ///< height of each plane
 } FlipContext;
 
 static int query_formats(AVFilterContext *ctx)
@@ -62,10 +63,14 @@ static int config_props(AVFilterLink *inlink)
 {
     FlipContext *s = inlink->dst->priv;
     const AVPixFmtDescriptor *pix_desc = av_pix_fmt_desc_get(inlink->format);
+    const int hsub = pix_desc->log2_chroma_w;
+    const int vsub = pix_desc->log2_chroma_h;
 
     av_image_fill_max_pixsteps(s->max_step, NULL, pix_desc);
-    s->hsub = pix_desc->log2_chroma_w;
-    s->vsub = pix_desc->log2_chroma_h;
+    s->planewidth[0]  = s->planewidth[3]  = inlink->w;
+    s->planewidth[1]  = s->planewidth[2]  = FF_CEIL_RSHIFT(inlink->w, hsub);
+    s->planeheight[0] = s->planeheight[3] = inlink->h;
+    s->planeheight[1] = s->planeheight[2] = FF_CEIL_RSHIFT(inlink->h, vsub);
 
     return 0;
 }
@@ -91,8 +96,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
         memcpy(out->data[1], in->data[1], AVPALETTE_SIZE);
 
     for (plane = 0; plane < 4 && in->data[plane] && in->linesize[plane]; plane++) {
-        const int width  = (plane == 1 || plane == 2) ? FF_CEIL_RSHIFT(inlink->w, s->hsub) : inlink->w;
-        const int height = (plane == 1 || plane == 2) ? FF_CEIL_RSHIFT(inlink->h, s->vsub) : inlink->h;
+        const int width  = s->planewidth[plane];
+        const int height = s->planeheight[plane];
         step = s->max_step[plane];
 
         outrow = out->data[plane];