Fix ImageSummary.Size value

The prune PR changed the meaning of the file to mean "space on disk
only unique to this image", this PR revert this change.

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

cli/command/formatter/image.go

@@ -226,8 +226,7 @@ func (c *imageContext) CreatedAt() string {
 
 func (c *imageContext) Size() string {
 	c.AddHeader(sizeHeader)
-	//NOTE: For backward compatibility we need to return VirtualSize
-	return units.HumanSizeWithPrecision(float64(c.i.VirtualSize), 3)
+	return units.HumanSizeWithPrecision(float64(c.i.Size), 3)
 }
 
 func (c *imageContext) Containers() string {
@@ -253,8 +252,8 @@ func (c *imageContext) SharedSize() string {
 
 func (c *imageContext) UniqueSize() string {
 	c.AddHeader(uniqueSizeHeader)
-	if c.i.Size == -1 {
+	if c.i.VirtualSize == -1 || c.i.SharedSize == -1 {
 		return "N/A"
 	}
-	return units.HumanSize(float64(c.i.Size))
+	return units.HumanSize(float64(c.i.VirtualSize - c.i.SharedSize))
 }

daemon/images.go

@@ -210,7 +210,6 @@ func (daemon *Daemon) Images(imageFilters filters.Args, all bool, withExtraAttrs
 			rootFS := *img.RootFS
 			rootFS.DiffIDs = nil
 
-			newImage.Size = 0
 			newImage.SharedSize = 0
 			for _, id := range img.RootFS.DiffIDs {
 				rootFS.Append(id)
@@ -223,8 +222,6 @@ func (daemon *Daemon) Images(imageFilters filters.Args, all bool, withExtraAttrs
 
 				if layerRefs[chid] > 1 {
 					newImage.SharedSize += diffSize
-				} else {
-					newImage.Size += diffSize
 				}
 			}
 		}
@@ -323,7 +320,7 @@ func newImage(image *image.Image, virtualSize int64) *types.ImageSummary {
 	newImage.ParentID = image.Parent.String()
 	newImage.ID = image.ID().String()
 	newImage.Created = image.Created.Unix()
-	newImage.Size = -1
+	newImage.Size = virtualSize
 	newImage.VirtualSize = virtualSize
 	newImage.SharedSize = -1
 	newImage.Containers = -1