Add masks.

src/pixie/images.nim

@@ -6,11 +6,6 @@ type
     width*, height*: int
     data*: seq[ColorRGBA]
 
-  Mask* = ref object
-    ## Main image object that holds the mask data.
-    width*, height*: int
-    data*: seq[uint8]
-
 proc newImage*(width, height: int): Image =
   ## Creates a new image with appropriate dimensions.
   result = Image()

src/pixie/masks.nim

@@ -0,0 +1,55 @@
+
+type
+  Mask* = ref object
+    ## Main mask object that holds the mask data.
+    width*, height*: int
+    data*: seq[uint8]
+
+proc newMask*(width, height: int): Mask =
+  ## Creates a new mask with appropriate dimensions.
+  result = Mask()
+  result.width = width
+  result.height = height
+  result.data = newSeq[uint8](width * height)
+
+proc inside*(mask: Mask, x, y: int): bool {.inline.} =
+  ## Returns true if (x, y) is inside the mask.
+  x >= 0 and x < mask.width and y >= 0 and y < mask.height
+
+proc copy*(mask: Mask): Mask =
+  ## Copies an mask creating a new mask.
+  result = newMask(mask.width, mask.height)
+  result.data = mask.data
+
+proc `$`*(mask: Mask): string =
+  ## Display the mask size and channels.
+  "<Mask " & $mask.width & "x" & $mask.height & ">"
+
+proc getRgbaUnsafe*(mask: Mask, x, y: int): uint8 {.inline.} =
+  ## Gets a alpha from (x, y) coordinates.
+  ## * No bounds checking *
+  ## Make sure that x, y are in bounds.
+  ## Failure in the assumptions will case unsafe memory reads.
+  result = mask.data[mask.width * y + x]
+
+proc `[]`*(mask: Mask, x, y: int): uint8 {.inline.} =
+  ## Gets a pixel at (x, y) or returns transparent black if outside of bounds.
+  if mask.inside(x, y):
+    return mask.getRgbaUnsafe(x, y)
+
+proc setRgbaUnsafe*(mask: Mask, x, y: int, alpha: uint8) {.inline.} =
+  ## Sets a color from (x, y) coordinates.
+  ## * No bounds checking *
+  ## Make sure that x, y are in bounds.
+  ## Failure in the assumptions will case unsafe memory writes.
+  mask.data[mask.width * y + x] = alpha
+
+proc `[]=`*(mask: Mask, x, y: int, alpha: uint8) {.inline.} =
+  ## Sets a pixel at (x, y) or does nothing if outside of bounds.
+  if mask.inside(x, y):
+    mask.setRgbaUnsafe(x, y, alpha)
+
+proc fill*(mask: Mask, alpha: uint8) =
+  ## Fills the mask with a solid color.
+  for i in 0 ..< mask.data.len:
+    mask.data[i] = alpha