From 8e441d402ba0e81798ccca49f8c48ba036dc5825 Mon Sep 17 00:00:00 2001
From: MacDue <macdue@dueutil.tech>
Date: Mon, 9 May 2022 00:01:21 +0100
Subject: [PATCH] LibGfx: Add Bitmap::solid_color()

This function returns an Optional<Color> and is given an
alpha_threshold. If all pixels above that alpha threshold are the
same color, it returns the color, otherwise it returns an empty
optional.
---
 Userland/Libraries/LibGfx/Bitmap.cpp | 17 +++++++++++++++++
 Userland/Libraries/LibGfx/Bitmap.h   |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/Userland/Libraries/LibGfx/Bitmap.cpp b/Userland/Libraries/LibGfx/Bitmap.cpp
index 35ba62d702..56619440b9 100644
--- a/Userland/Libraries/LibGfx/Bitmap.cpp
+++ b/Userland/Libraries/LibGfx/Bitmap.cpp
@@ -608,4 +608,21 @@ bool Bitmap::visually_equals(Bitmap const& other) const
     return true;
 }
 
+Optional<Color> Bitmap::solid_color(u8 alpha_threshold) const
+{
+    Optional<Color> color;
+    for (auto y = 0; y < height(); ++y) {
+        for (auto x = 0; x < width(); ++x) {
+            auto const& pixel = get_pixel(x, y);
+            if (has_alpha_channel() && pixel.alpha() <= alpha_threshold)
+                continue;
+            if (!color.has_value())
+                color = pixel;
+            else if (pixel != color)
+                return {};
+        }
+    }
+    return color;
+}
+
 }
diff --git a/Userland/Libraries/LibGfx/Bitmap.h b/Userland/Libraries/LibGfx/Bitmap.h
index 968ab77087..f556a25f52 100644
--- a/Userland/Libraries/LibGfx/Bitmap.h
+++ b/Userland/Libraries/LibGfx/Bitmap.h
@@ -240,6 +240,8 @@ public:
 
     [[nodiscard]] bool visually_equals(Bitmap const&) const;
 
+    [[nodiscard]] Optional<Color> solid_color(u8 alpha_threshold = 0) const;
+
 private:
     Bitmap(BitmapFormat, IntSize const&, int, BackingStore const&);
     Bitmap(BitmapFormat, IntSize const&, int, size_t pitch, void*);