Fix flip.

src/pixie/images.nim

@@ -126,17 +126,25 @@ proc magnifyBy2*(image: Image): Image =
 
 proc flipHorizontal*(image: Image) =
   ## Flips the image around the Y axis.
+  let w = image.width div 2
   for y in 0 ..< image.height:
-    for x in 0 ..< image.width:
-      let rgba = image.getRgbaUnsafe(x, y)
-      image.setRgbaUnsafe(image.width - x - 1, y, rgba)
+    for x in 0 ..< w:
+      let
+        rgba1 = image.getRgbaUnsafe(x, y)
+        rgba2 = image.getRgbaUnsafe(image.width - x - 1, y)
+      image.setRgbaUnsafe(image.width - x - 1, y, rgba1)
+      image.setRgbaUnsafe(x, y, rgba2)
 
 proc flipVertical*(image: Image) =
   ## Flips the image around the X axis.
-  for y in 0 ..< image.height:
+  let h = image.height div 2
+  for y in 0 ..< h:
     for x in 0 ..< image.width:
-      let rgba = image.getRgbaUnsafe(x, y)
-      image.setRgbaUnsafe(x, image.height - y - 1, rgba)
+      let
+        rgba1 = image.getRgbaUnsafe(x, y)
+        rgba2 = image.getRgbaUnsafe(x, image.height - y - 1)
+      image.setRgbaUnsafe(x, image.height - y - 1, rgba1)
+      image.setRgbaUnsafe(x, y, rgba2)
 
 func lerp(a, b: Color, v: float32): Color {.inline.} =
   result.r = lerp(a.r, b.r, v)

tests/test_flips.nim

@@ -0,0 +1,16 @@
+import pixie, chroma, vmath
+
+block:
+
+  var a = newImage(101, 101)
+  a.fill(rgba(255, 0, 0, 255))
+  var b = newImage(50, 50)
+  b.fill(rgba(0, 255, 0, 255))
+
+  a.draw(b, vec2(0, 0))
+
+  a.writeFile("tests/images/flipped1.png")
+  a.flipVertical()
+  a.writeFile("tests/images/flipped2.png")
+  a.flipHorizontal()
+  a.writeFile("tests/images/flipped3.png")