Reduce memory usage when scaling down animated images

CHANGELOG.md

@@ -14,6 +14,7 @@
 - Don't set `Expires` HTTP header as it is ignored if the `Cache-Control` header is set.
 - Don't log health-check requests and responses.
 - Enforce `IMGPROXY_WORKERS=1` when running in AWS Lambda.
+- Reduce memory usage when scaling down animated images.
 - (pro) If the `step` argument of the `video_thumbnail_tile` is negative, calculate `step` automatically.
 
 ### Fix

processing/processing.go

@@ -162,6 +162,16 @@ func transformAnimated(ctx context.Context, img *vips.Image, po *options.Process
 		if err = mainPipeline.Run(ctx, frame, po, nil); err != nil {
 			return err
 		}
+
+		if r, _ := frame.GetIntDefault("imgproxy-scaled-down", 0); r == 1 {
+			if err = frame.CopyMemory(); err != nil {
+				return err
+			}
+
+			if err = router.CheckTimeout(ctx); err != nil {
+				return err
+			}
+		}
 	}
 
 	if err = img.Arrayjoin(frames); err != nil {

vips/vips.c

@@ -804,7 +804,7 @@ vips_strip(VipsImage *in, VipsImage **out, int keep_exif_copyright)
         (strcmp(name, "vips-loader") == 0) ||
         (strcmp(name, "background") == 0) ||
         (strcmp(name, "vips-sequential") == 0) ||
-        (strcmp(name, "imgproxy-dpr-scale") == 0))
+        (vips_isprefix("imgproxy-", name)))
       continue;
 
     if (keep_exif_copyright) {

vips/vips.go

@@ -606,6 +606,10 @@ func (img *Image) Resize(wscale, hscale float64) error {
 		return Error()
 	}
 
+	if wscale < 1.0 || hscale < 1.0 {
+		C.vips_image_set_int(tmp, cachedCString("imgproxy-scaled-down"), 1)
+	}
+
 	C.swap_and_clear(&img.VipsImage, tmp)
 
 	return nil