add-raw-pixel-buffer-to-image: addressed review comments

- Moved to use function to determine api specific alpha/byte format
  type.
- Updated infra submodule to latest master, in order to have
  `is_little_endian` function for example.
- Updated copyright

.gitmodules

@@ -2,3 +2,4 @@
 [submodule "lib/infra"]
 	path = lib/infra
 	url = https://github.com/cycfi/infra
+	branch = master

examples/image_pixmap_chessboard.cpp

@@ -1,20 +1,12 @@
 /*=============================================================================
-   Copyright (c) 2016-2020 Joel de Guzman
+   Copyright (c) 2016-2020 Brent Soles
 
    Distributed under the MIT License (https://opensource.org/licenses/MIT)
 =============================================================================*/
 #include "app.hpp"
 
 using namespace cycfi::artist;
 
-bool constexpr is_little_endian() {
-   union {
-      uint32_t i;
-      char c[4];
-   } cmp = {0x01020304};
-   return !(cmp.c[0] == 1);
-}
-
 int constexpr rows = 8;
 int constexpr cols = 8;
 int constexpr square_side = 100;
@@ -25,7 +17,7 @@ size_t constexpr pix_buf_size = rows * cols * square_area;
 
 uint32_t constexpr white = 0xffffffff;
 // on little endian systems RGBA is formatted as ABGR for values
-std::function<uint32_t()> black = []() { return is_little_endian() ? 0xff000000 : 0x000000ff; };
+std::function<uint32_t()> black = []() { return cycfi::is_little_endian() ? 0xff000000 : 0x000000ff; };
 
 auto constexpr window_size = extent{
    static_cast<float>(cols * square_side),

lib/impl/skia/image.cpp

@@ -26,13 +26,22 @@ using std::pair;
 
 namespace cycfi::artist
 {
-   static const map<img_fmt, pair<SkAlphaType, SkColorType>> _img_fmt_map_to_api_type = {
-      {img_fmt::INVALID, {SkAlphaType::kUnknown_SkAlphaType, SkColorType::kUnknown_SkColorType}},
-      {img_fmt::GRAY8, {SkAlphaType::kOpaque_SkAlphaType, SkColorType::kGray_8_SkColorType}},
-      {img_fmt::RGB16, {SkAlphaType::kOpaque_SkAlphaType, SkColorType::kRGB_565_SkColorType}},
-      {img_fmt::RGB32, {SkAlphaType::kOpaque_SkAlphaType, SkColorType::kRGB_888x_SkColorType}},
-      {img_fmt::RGBA32, {SkAlphaType::kOpaque_SkAlphaType, SkColorType::kRGBA_8888_SkColorType}}
-   };
+   pair<SkAlphaType, SkColorType> _map_img_fmt_to_api_type(const img_fmt& fmt)
+   {
+      switch(fmt)
+      {
+         case img_fmt::GRAY8:
+            return {SkAlphaType::kOpaque_SkAlphaType, SkColorType::kGray_8_SkColorType};
+         case img_fmt::RGB16:
+            return {SkAlphaType::kOpaque_SkAlphaType, SkColorType::kRGB_565_SkColorType};
+         case img_fmt::RGB32:
+            return {SkAlphaType::kOpaque_SkAlphaType, SkColorType::kRGB_888x_SkColorType};
+         case img_fmt::RGBA32:
+            return {SkAlphaType::kOpaque_SkAlphaType, SkColorType::kRGBA_8888_SkColorType};
+         default:
+            return {SkAlphaType::kUnknown_SkAlphaType, SkColorType::kUnknown_SkColorType};
+      }
+   }
 
    image::image(extent size)
     : _impl{ new artist::image_impl(size) }
@@ -70,7 +79,7 @@ namespace cycfi::artist
       SkAlphaType alpha_fmt;
       SkColorType byte_fmt;
       try {
-         std::tie(alpha_fmt, byte_fmt) = _img_fmt_map_to_api_type.at(fmt);
+         std::tie(alpha_fmt, byte_fmt) = _map_img_fmt_to_api_type(fmt);
       } catch(std::exception& /* e */) {
          throw std::runtime_error{ "Error: unrecognized format." };
       }