Fix for [#25713] VSE shows and renders wrong straight alpha gradient even after convert to premul is checked

* Caching of the start and end stills were just referencing the original imbuf (which got premultiplied after the caching), so as a result most of the time the premul was applied twice.
* Now the start and end stills are stored in the cache as duplicates of the original (non modified) imbuf.

2 files changed, 5 insertions, 4 deletions

diff --git a/source/blender/blenkernel/intern/seqcache.c b/source/blender/blenkernel/intern/seqcache.c
index 122e186bcd7..78cd4bb51fe 100644
--- a/source/blender/blenkernel/intern/seqcache.c
+++ b/source/blender/blenkernel/intern/seqcache.c
@@ -232,8 +232,9 @@ void seq_stripelem_cache_put(
 	key->cfra = cfra - seq->start;
 	key->type = type;
 
-	/* we want our own version */
-	IMB_refImBuf(i);
+	/* Normally we want our own version, but start and end stills are duplicates of the original. */
+	if(ELEM(type, SEQ_STRIPELEM_IBUF_STARTSTILL, SEQ_STRIPELEM_IBUF_ENDSTILL)==0)
+		IMB_refImBuf(i);
 
 	e = (seqCacheEntry*) BLI_mempool_alloc(entrypool);
 
diff --git a/source/blender/blenkernel/intern/sequencer.c b/source/blender/blenkernel/intern/sequencer.c
index 9ffc04c5191..973f14d690c 100644
--- a/source/blender/blenkernel/intern/sequencer.c
+++ b/source/blender/blenkernel/intern/sequencer.c
@@ -1705,13 +1705,13 @@ static void copy_to_ibuf_still(SeqRenderData context, Sequence * seq, float nr,
 	if (nr == 0) {
 		seq_stripelem_cache_put(
 			context, seq, seq->start, 
-			SEQ_STRIPELEM_IBUF_STARTSTILL, ibuf);
+			SEQ_STRIPELEM_IBUF_STARTSTILL, IMB_dupImBuf(ibuf));
 	} 
 
 	if (nr == seq->len - 1) {
 		seq_stripelem_cache_put(
 			context, seq, seq->start, 
-			SEQ_STRIPELEM_IBUF_ENDSTILL, ibuf);
+			SEQ_STRIPELEM_IBUF_ENDSTILL, IMB_dupImBuf(ibuf));
 	}
 }