LibWeb: Implement <feComposite> SVG filter

Author: https://github.com/tcl3
Commit: a00e7cb20b
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5744
Reviewed-by: https://github.com/gmta ✅
Reviewed-by: https://github.com/konradekk

Libraries/LibGfx/Filter.cpp

@@ -9,6 +9,7 @@
 #include <LibGfx/SkiaUtils.h>
 #include <core/SkBlendMode.h>
 #include <core/SkColorFilter.h>
+#include <core/SkScalar.h>
 #include <effects/SkColorMatrix.h>
 #include <effects/SkImageFilters.h>
 
@@ -41,6 +42,16 @@ FilterImpl const& Filter::impl() const
     return *m_impl;
 }
 
+Filter Filter::arithmetic(Optional<Filter const&> background, Optional<Filter const&> foreground, float k1, float k2, float k3, float k4)
+{
+    sk_sp<SkImageFilter> background_skia = background.has_value() ? background->m_impl->filter : nullptr;
+    sk_sp<SkImageFilter> foreground_skia = foreground.has_value() ? foreground->m_impl->filter : nullptr;
+
+    auto filter = SkImageFilters::Arithmetic(
+        SkFloatToScalar(k1), SkFloatToScalar(k2), SkFloatToScalar(k3), SkFloatToScalar(k4), false, move(background_skia), move(foreground_skia));
+    return Filter(Impl::create(filter));
+}
+
 Filter Filter::compose(Filter const& outer, Filter const& inner)
 {
     auto inner_skia = inner.m_impl->filter;