Fix Image.rounded/1 and Image.squircle/1 when the image has an alpha band. Closes #182

Author: kipcole9

CHANGELOG.md

@@ -1,5 +1,13 @@
 # Changelog
 
+## Image 0.59.2
+
+This is the changelog for Image version 0.59.1 released on April 21st, 2025.  For older changelogs please consult the release tag on [GitHub](https://github.com/elixir-image/image/tags)
+
+### Bug Fixes
+
+* Fixes `Image.rounded/1` and `Image.squircle/1` when the image has an alpha band. Thanks to @Neophen for the report. Closes #182.
+
 ## Image 0.59.1
 
 This is the changelog for Image version 0.59.1 released on April 21st, 2025.  For older changelogs please consult the release tag on [GitHub](https://github.com/elixir-image/image/tags)

lib/image.ex

@@ -6049,16 +6049,26 @@ defmodule Image do
   * `{:error, reason}`
 
   """
-  @doc subject: "Generator"
+  @doc subject: "Mask"
 
   @spec rounded(Vimage.t(), Keyword.t()) :: {:ok, Vimage.t()} | {:error, error_message()}
   def rounded(%Vimage{} = image, options \\ []) do
+    use Image.Math
+
     options = Keyword.put_new(options, :radius, @default_round_corner_radius)
     width = width(image)
     height = height(image)
 
     {:ok, mask} = mask(:rounded_corners, width, height, options)
-    Operation.bandjoin([image, mask])
+
+    case split_alpha(image) do
+      {base_image, nil} ->
+        Operation.bandjoin([base_image, mask])
+
+      {base_image, alpha} ->
+        alpha = if_then_else!(mask == 0, mask, alpha)
+        Operation.bandjoin([base_image, alpha])
+    end
   end
 
   @doc """
@@ -6118,12 +6128,22 @@ defmodule Image do
 
   @spec squircle(Vimage.t(), Keyword.t()) :: {:ok, Vimage.t()} | {:error, error_message()}
   def squircle(%Vimage{} = image, options \\ []) do
+    use Image.Math
+
     options = Keyword.put_new(options, :radius, @default_squircle_radius)
     width = width(image)
     height = height(image)
 
     {:ok, mask} = mask(:squircle, width, height, options)
-    Operation.bandjoin([image, mask])
+
+    case split_alpha(image) do
+      {base_image, nil} ->
+        Operation.bandjoin([base_image, mask])
+
+      {base_image, alpha} ->
+        alpha = if_then_else!(mask == 0, mask, alpha)
+        Operation.bandjoin([base_image, alpha])
+    end
   end
 
   @doc """

mix.exs

@@ -1,7 +1,7 @@
 defmodule Image.MixProject do
   use Mix.Project
 
-  @version "0.59.1"
+  @version "0.59.2"
 
   @app_name "image"
 

test/image_test.exs

@@ -67,6 +67,38 @@ defmodule Image.Test do
     assert_images_equal(out_path, validate_path("Kip_small_squircle_mask.png"))
   end
 
+  test "Rounded Image with alpha", %{dir: dir} do
+    image = image_path("Kip_small.jpg")
+    validate_path = validate_path("Kip_small_alpha_rounded_mask.png")
+
+    {:ok, kip} = Vimage.new_from_file(image)
+    {:ok, kip} = Image.add_alpha(kip, 255)
+    {:ok, rounded} = Image.rounded(kip)
+
+    out_path = Temp.path!(suffix: ".png", basedir: dir)
+    assert :ok = Vimage.write_to_file(rounded, out_path)
+
+    # {:ok, _} = Image.write(rounded, validate_path)
+
+    assert_images_equal(out_path, validate_path)
+  end
+
+  test "Squircled Image with alpha", %{dir: dir} do
+    image = image_path("Kip_small.jpg")
+    validate_path = validate_path("Kip_small_alpha_squircle_mask.png")
+
+    {:ok, kip} = Vimage.new_from_file(image)
+    {:ok, kip} = Image.add_alpha(kip, 255)
+    {:ok, squircled} = Image.squircle(kip)
+
+    out_path = Temp.path!(suffix: ".png", basedir: dir)
+    assert :ok = Vimage.write_to_file(squircled, out_path)
+
+    # {:ok, _} = Image.write(squircled, validate_path)
+
+    assert_images_equal(out_path, validate_path)
+  end
+
   test "Image composition", %{dir: dir} do
     image = image_path("lamborghini-forsennato-concept.jpg")