bugfix for minifyBy2 power > 1

src/pixie/images.nim

@@ -176,15 +176,16 @@ proc minifyBy2*(image: Image, power = 1): Image =
   if power == 0:
     return image.copy()
 
+  var src = image
   for i in 1 .. power:
-    result = newImage(image.width div 2, image.height div 2)
+    result = newImage(src.width div 2, src.height div 2)
     for y in 0 ..< result.height:
       for x in 0 ..< result.width:
         let
-          a = image.getRgbaUnsafe(x * 2 + 0, y * 2 + 0)
-          b = image.getRgbaUnsafe(x * 2 + 1, y * 2 + 0)
-          c = image.getRgbaUnsafe(x * 2 + 1, y * 2 + 1)
-          d = image.getRgbaUnsafe(x * 2 + 0, y * 2 + 1)
+          a = src.getRgbaUnsafe(x * 2 + 0, y * 2 + 0)
+          b = src.getRgbaUnsafe(x * 2 + 1, y * 2 + 0)
+          c = src.getRgbaUnsafe(x * 2 + 1, y * 2 + 1)
+          d = src.getRgbaUnsafe(x * 2 + 0, y * 2 + 1)
 
         let color = rgba(
           ((a.r.uint32 + b.r + c.r + d.r) div 4).uint8,
@@ -195,6 +196,9 @@ proc minifyBy2*(image: Image, power = 1): Image =
 
         result.setRgbaUnsafe(x, y, color)
 
+    # Set src as this result for if we do another power
+    src = result
+
 proc magnifyBy2*(image: Image, power = 1): Image =
   ## Scales image image up by 2 ^ power.
   if power < 0:

tests/test_images.nim

@@ -85,3 +85,9 @@ block:
     a = readImage("tests/images/flipped1.png")
     b = a.minifyBy2()
   b.writeFile("tests/images/minifiedBy2.png")
+
+block:
+  let
+    a = readImage("tests/images/flipped1.png")
+    b = a.minifyBy2(2)
+  b.writeFile("tests/images/minifiedBy4.png")