[FFmpeg-devel] [PATCH 07/17] swscale/graph: settle colorspace metadata before scaling

[Niklas Haas]

From: Niklas Haas <git at haasn.dev>

Take special care to handle grayscale formats without a colorspace
gracefully.
---
 libswscale/graph.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/libswscale/graph.c b/libswscale/graph.c
index fbad1fe8c3..36b74fad0c 100644
--- a/libswscale/graph.c
+++ b/libswscale/graph.c
@@ -521,8 +521,21 @@ int sws_graph_create(SwsContext *ctx, const SwsFormat *dst, const SwsFormat *src
     graph->field = field;
     graph->opts_copy = *ctx;
 
-    graph->exec.input.fmt  = src->format;
-    graph->exec.output.fmt = dst->format;
+    /**
+     * Grayspace does not really have primaries, so just force the use of
+     * the equivalent other primary set to avoid a conversion. Technically,
+     * this does affect the weights used for the Grayscale conversion, but
+     * in practise, that should give the expected results more often than not.
+     */
+    if (isGray(dst->format)) {
+        graph->dst.color = graph->src.color;
+    } else if (isGray(src->format)) {
+        graph->src.color = graph->dst.color;
+    }
+
+    graph->incomplete = ff_infer_colors(&graph->src.color, &graph->dst.color);
+    graph->exec.input.fmt  = graph->src.format;
+    graph->exec.output.fmt = graph->dst.format;
 
     ret = avpriv_slicethread_create(&graph->slicethread, (void *) graph,
                                     sws_graph_worker, NULL, ctx->threads);
-- 
2.47.0