save work if no shadow offset

src/pixie/images.nim

@@ -976,12 +976,18 @@ proc shadow*(
   image: Image, offset: Vec2, spread, blur: float32, color: SomeColor
 ): Image {.raises: [PixieError].} =
   ## Create a shadow of the image with the offset, spread and blur.
-  let
-    mask = image.newMask()
+  let mask = image.newMask()
+
+  var shifted: Mask
+  if offset == vec2(0, 0):
+    shifted = mask
+  else:
     shifted = newMask(mask.width, mask.height)
-  shifted.draw(mask, translate(offset), bmOverwrite)
+    shifted.draw(mask, translate(offset), bmOverwrite)
+
   shifted.spread(spread)
   shifted.blur(blur)
+
   result = newImage(shifted.width, shifted.height)
   result.fill(color)
   result.draw(shifted, blendMode = bmMask)

tests/benchmark_images_draw.nim

@@ -115,7 +115,7 @@ block:
     a = newImage(100, 100)
     b = newImage(50, 50)
 
-  timeIt "shadow":
+  timeIt "shadow (no offset)":
     b.fill(rgba(0, 0, 0, 255))
     a.draw(b, translate(vec2(25, 25)))
 
@@ -126,3 +126,20 @@ block:
       color = rgba(0, 0, 0, 255)
     )
     keep(shadow)
+
+block:
+  let
+    a = newImage(100, 100)
+    b = newImage(50, 50)
+
+  timeIt "shadow (with offset)":
+    b.fill(rgba(0, 0, 0, 255))
+    a.draw(b, translate(vec2(25, 25)))
+
+    let shadow = a.shadow(
+      offset = vec2(10, 10),
+      spread = 10,
+      blur = 10,
+      color = rgba(0, 0, 0, 255)
+    )
+    keep(shadow)