source/blender/blenkernel/BKE_blender_version.h

@@ -29,7 +29,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 17
+#define BLENDER_FILE_SUBVERSION 18
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and cancel loading the file, showing a warning to

source/blender/blenloader/intern/versioning_400.cc

@@ -27,6 +27,7 @@
 #include "DNA_modifier_types.h"
 #include "DNA_movieclip_types.h"
 #include "DNA_scene_types.h"
+#include "DNA_sequence_types.h"
 #include "DNA_world_types.h"
 
 #include "DNA_defaults.h"
@@ -61,6 +62,7 @@
 #include "BKE_scene.h"
 #include "BKE_tracking.h"
 
+#include "SEQ_iterator.hh"
 #include "SEQ_retiming.hh"
 #include "SEQ_sequencer.hh"
 
@@ -1936,6 +1938,15 @@ static void fix_geometry_nodes_object_info_scale(bNodeTree &ntree)
   }
 }
 
+static bool seq_filter_bilinear_to_auto(Sequence *seq, void * /*user_data*/)
+{
+  StripTransform *transform = seq->strip->transform;
+  if (transform != nullptr && transform->filter == SEQ_TRANSFORM_FILTER_BILINEAR) {
+    transform->filter = SEQ_TRANSFORM_FILTER_AUTO;
+  }
+  return true;
+}
+
 void blo_do_versions_400(FileData *fd, Library * /*lib*/, Main *bmain)
 {
   if (!MAIN_VERSION_FILE_ATLEAST(bmain, 400, 1)) {
@@ -2848,6 +2859,14 @@ void blo_do_versions_400(FileData *fd, Library * /*lib*/, Main *bmain)
     }
   }
 
+  if (!MAIN_VERSION_FILE_ATLEAST(bmain, 401, 18)) {
+    LISTBASE_FOREACH (Scene *, scene, &bmain->scenes) {
+      if (scene->ed != nullptr) {
+        SEQ_for_each_callback(&scene->ed->seqbase, seq_filter_bilinear_to_auto, nullptr);
+      }
+    }
+  }
+
   /**
    * Always bump subversion in BKE_blender_version.h when adding versioning
    * code here, and wrap it inside a MAIN_VERSION_FILE_ATLEAST check.

source/blender/makesdna/DNA_sequence_types.h

@@ -836,6 +836,7 @@ typedef enum SequenceColorTag {
 
 /* Sequence->StripTransform->filter */
 enum {
+  SEQ_TRANSFORM_FILTER_AUTO = -1,
   SEQ_TRANSFORM_FILTER_NEAREST = 0,
   SEQ_TRANSFORM_FILTER_BILINEAR = 1,
   SEQ_TRANSFORM_FILTER_BOX = 2,

source/blender/makesrna/intern/rna_sequencer.cc

@@ -1696,6 +1696,11 @@ static void rna_def_strip_crop(BlenderRNA *brna)
 }
 
 static const EnumPropertyItem transform_filter_items[] = {
+    {SEQ_TRANSFORM_FILTER_AUTO,
+     "AUTO",
+     0,
+     "Auto",
+     "Automatically choose filter based on scaling factor"},
     {SEQ_TRANSFORM_FILTER_NEAREST, "NEAREST", 0, "Nearest", "Use nearest sample"},
     {SEQ_TRANSFORM_FILTER_BILINEAR,
      "BILINEAR",
@@ -1770,7 +1775,7 @@ static void rna_def_strip_transform(BlenderRNA *brna)
   prop = RNA_def_property(srna, "filter", PROP_ENUM, PROP_NONE);
   RNA_def_property_enum_sdna(prop, nullptr, "filter");
   RNA_def_property_enum_items(prop, transform_filter_items);
-  RNA_def_property_enum_default(prop, SEQ_TRANSFORM_FILTER_BILINEAR);
+  RNA_def_property_enum_default(prop, SEQ_TRANSFORM_FILTER_AUTO);
   RNA_def_property_ui_text(prop, "Filter", "Type of filter to use for image transformation");
   RNA_def_property_update(prop, NC_SCENE | ND_SEQUENCER, "rna_SequenceTransform_update");
 

source/blender/sequencer/intern/render.cc

@@ -500,6 +500,30 @@ static bool seq_image_transform_transparency_gained(const SeqRenderData *context
                               seq_image_quad[3]);
 }
 
+/* Automatic filter:
+ * - No scale, no rotation and non-fractional position: nearest.
+ * - Scale up by more than 2x: cubic mitchell.
+ * - Scale down by more than 2x: box.
+ * - Otherwise: bilinear. */
+static eIMBInterpolationFilterMode get_auto_filter(const StripTransform *transform)
+{
+  const float sx = fabsf(transform->scale_x);
+  const float sy = fabsf(transform->scale_y);
+  if (sx > 2.0f && sy > 2.0f) {
+    return IMB_FILTER_CUBIC_MITCHELL;
+  }
+  if (sx < 0.5f && sy < 0.5f) {
+    return IMB_FILTER_BOX;
+  }
+  const float px = transform->xofs;
+  const float py = transform->yofs;
+  const float rot = transform->rotation;
+  if (sx == 1.0f && sy == 1.0f && roundf(px) == px && roundf(py) == py && rot == 0.0f) {
+    return IMB_FILTER_NEAREST;
+  }
+  return IMB_FILTER_BILINEAR;
+}
+
 static void sequencer_preprocess_transform_crop(
     ImBuf *in, ImBuf *out, const SeqRenderData *context, Sequence *seq, const bool is_proxy_image)
 {
@@ -524,6 +548,9 @@ static void sequencer_preprocess_transform_crop(
   const StripTransform *transform = seq->strip->transform;
   eIMBInterpolationFilterMode filter = IMB_FILTER_NEAREST;
   switch (transform->filter) {
+    case SEQ_TRANSFORM_FILTER_AUTO:
+      filter = get_auto_filter(seq->strip->transform);
+      break;
     case SEQ_TRANSFORM_FILTER_NEAREST:
       filter = IMB_FILTER_NEAREST;
       break;

source/blender/sequencer/intern/sequencer.cc

@@ -77,7 +77,7 @@ static Strip *seq_strip_alloc(int type)
     strip->transform->scale_y = 1;
     strip->transform->origin[0] = 0.5f;
     strip->transform->origin[1] = 0.5f;
-    strip->transform->filter = SEQ_TRANSFORM_FILTER_BILINEAR;
+    strip->transform->filter = SEQ_TRANSFORM_FILTER_AUTO;
     strip->crop = static_cast<StripCrop *>(MEM_callocN(sizeof(StripCrop), "StripCrop"));
   }