From 8ea4375d4ad050cc869ebaf52edd8389c0da8bca Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Tue, 2 Jun 2020 17:34:56 +0200
Subject: [PATCH] LibGfx: Templatize some of the scanline unpacking code

---
 Libraries/LibGfx/PNGLoader.cpp | 113 +++++++++++++++------------------
 1 file changed, 52 insertions(+), 61 deletions(-)

diff --git a/Libraries/LibGfx/PNGLoader.cpp b/Libraries/LibGfx/PNGLoader.cpp
index 65090e3e79..584b77bc6c 100644
--- a/Libraries/LibGfx/PNGLoader.cpp
+++ b/Libraries/LibGfx/PNGLoader.cpp
@@ -299,33 +299,60 @@ ALWAYS_INLINE static void unfilter_impl(Gfx::Bitmap& bitmap, int y, const void*
     }
 }
 
+template<typename T>
+ALWAYS_INLINE static void unpack_grayscale_without_alpha(PNGLoadingContext& context)
+{
+    for (int y = 0; y < context.height; ++y) {
+        auto* gray_values = reinterpret_cast<const T*>(context.scanlines[y].data.data());
+        for (int i = 0; i < context.width; ++i) {
+            auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
+            pixel.r = gray_values[i];
+            pixel.g = gray_values[i];
+            pixel.b = gray_values[i];
+            pixel.a = 0xff;
+        }
+    }
+}
+
+template<typename T>
+ALWAYS_INLINE static void unpack_grayscale_with_alpha(PNGLoadingContext& context)
+{
+    for (int y = 0; y < context.height; ++y) {
+        auto* tuples = reinterpret_cast<const Tuple<T>*>(context.scanlines[y].data.data());
+        for (int i = 0; i < context.width; ++i) {
+            auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
+            pixel.r = tuples[i].gray;
+            pixel.g = tuples[i].gray;
+            pixel.b = tuples[i].gray;
+            pixel.a = tuples[i].a;
+        }
+    }
+}
+
+template<typename T>
+ALWAYS_INLINE static void unpack_triplets_without_alpha(PNGLoadingContext& context)
+{
+    for (int y = 0; y < context.height; ++y) {
+        auto* triplets = reinterpret_cast<const Triplet<T>*>(context.scanlines[y].data.data());
+        for (int i = 0; i < context.width; ++i) {
+            auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
+            pixel.r = triplets[i].r;
+            pixel.g = triplets[i].g;
+            pixel.b = triplets[i].b;
+            pixel.a = 0xff;
+        }
+    }
+}
+
 NEVER_INLINE FLATTEN static void unfilter(PNGLoadingContext& context)
 {
     // First unpack the scanlines to RGBA:
     switch (context.color_type) {
     case 0:
         if (context.bit_depth == 8) {
-            for (int y = 0; y < context.height; ++y) {
-                auto* gray_values = (u8*)context.scanlines[y].data.data();
-                for (int i = 0; i < context.width; ++i) {
-                    auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
-                    pixel.r = gray_values[i];
-                    pixel.g = gray_values[i];
-                    pixel.b = gray_values[i];
-                    pixel.a = 0xff;
-                }
-            }
+            unpack_grayscale_without_alpha<u8>(context);
         } else if (context.bit_depth == 16) {
-            for (int y = 0; y < context.height; ++y) {
-                auto* gray_values = (u16*)context.scanlines[y].data.data();
-                for (int i = 0; i < context.width; ++i) {
-                    auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
-                    pixel.r = gray_values[i] & 0xFF;
-                    pixel.g = gray_values[i] & 0xFF;
-                    pixel.b = gray_values[i] & 0xFF;
-                    pixel.a = 0xff;
-                }
-            }
+            unpack_grayscale_without_alpha<u16>(context);
         } else if (context.bit_depth == 1 || context.bit_depth == 2 || context.bit_depth == 4) {
             auto pixels_per_byte = 8 / context.bit_depth;
             auto mask = (1 << context.bit_depth) - 1;
@@ -347,54 +374,18 @@ NEVER_INLINE FLATTEN static void unfilter(PNGLoadingContext& context)
         break;
     case 4:
         if (context.bit_depth == 8) {
-            for (int y = 0; y < context.height; ++y) {
-                auto* tuples = (Tuple<u8>*)context.scanlines[y].data.data();
-                for (int i = 0; i < context.width; ++i) {
-                    auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
-                    pixel.r = tuples[i].gray;
-                    pixel.g = tuples[i].gray;
-                    pixel.b = tuples[i].gray;
-                    pixel.a = tuples[i].a;
-                }
-            }
+            unpack_grayscale_with_alpha<u8>(context);
         } else if (context.bit_depth == 16) {
-            for (int y = 0; y < context.height; ++y) {
-                auto* tuples = (Tuple<u16>*)context.scanlines[y].data.data();
-                for (int i = 0; i < context.width; ++i) {
-                    auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
-                    pixel.r = tuples[i].gray & 0xFF;
-                    pixel.g = tuples[i].gray & 0xFF;
-                    pixel.b = tuples[i].gray & 0xFF;
-                    pixel.a = tuples[i].a & 0xFF;
-                }
-            }
+            unpack_grayscale_with_alpha<u16>(context);
         } else {
             ASSERT_NOT_REACHED();
         }
         break;
     case 2:
         if (context.bit_depth == 8) {
-            for (int y = 0; y < context.height; ++y) {
-                auto* triplets = (Triplet<u8>*)context.scanlines[y].data.data();
-                for (int i = 0; i < context.width; ++i) {
-                    auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
-                    pixel.r = triplets[i].r;
-                    pixel.g = triplets[i].g;
-                    pixel.b = triplets[i].b;
-                    pixel.a = 0xff;
-                }
-            }
+            unpack_triplets_without_alpha<u8>(context);
         } else if (context.bit_depth == 16) {
-            for (int y = 0; y < context.height; ++y) {
-                auto* triplets = (Triplet<u16>*)context.scanlines[y].data.data();
-                for (int i = 0; i < context.width; ++i) {
-                    auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
-                    pixel.r = triplets[i].r & 0xFF;
-                    pixel.g = triplets[i].g & 0xFF;
-                    pixel.b = triplets[i].b & 0xFF;
-                    pixel.a = 0xff;
-                }
-            }
+            unpack_grayscale_without_alpha<u16>(context);
         } else {
             ASSERT_NOT_REACHED();
         }
@@ -406,7 +397,7 @@ NEVER_INLINE FLATTEN static void unfilter(PNGLoadingContext& context)
             }
         } else if (context.bit_depth == 16) {
             for (int y = 0; y < context.height; ++y) {
-                auto* triplets = (Quad<u16>*)context.scanlines[y].data.data();
+                auto* triplets = reinterpret_cast<const Quad<u16>*>(context.scanlines[y].data.data());
                 for (int i = 0; i < context.width; ++i) {
                     auto& pixel = (Pixel&)context.bitmap->scanline(y)[i];
                     pixel.r = triplets[i].r & 0xFF;