Added image_transform example.

examples/CMakeLists.txt

@@ -47,6 +47,13 @@ target_compile_definitions(image_rotate PRIVATE ${SELENE_COMPILER_DEFINITIONS})
 target_include_directories(image_rotate PRIVATE ${SELENE_DIR}/examples ${Boost_INCLUDE_DIR})
 target_link_libraries(image_rotate selene ${SELENE_BOOST_TARGET_NAME})
 
+add_executable(image_transform
+        ${CMAKE_CURRENT_LIST_DIR}/image_transform.cpp)
+target_compile_options(image_transform PRIVATE ${SELENE_COMPILER_OPTIONS})
+target_compile_definitions(image_transform PRIVATE ${SELENE_COMPILER_DEFINITIONS})
+target_include_directories(image_transform PRIVATE ${SELENE_DIR}/examples ${Boost_INCLUDE_DIR})
+target_link_libraries(image_transform selene ${SELENE_BOOST_TARGET_NAME})
+
 add_executable(readme_example
         ${CMAKE_CURRENT_LIST_DIR}/readme_example.cpp)
 target_compile_options(readme_example PRIVATE ${SELENE_COMPILER_OPTIONS})

examples/image_conversion.cpp

@@ -29,7 +29,7 @@ int main(int argc, char** argv)
 
   const auto img_rgb = sln_examples::read_example_image<Pixel_8u3>("bike_duck.png", data_path);
 
-  // We will now perform three conversions:
+  // We will now perform three color format conversions:
   // - From RGB to Y (grayscale)
   std::cout << "Converting the image from RGB to Y (grayscale)...\n";
   const auto img_y = convert_image<PixelFormat::RGB, PixelFormat::Y>(img_rgb);

examples/image_transform.cpp

@@ -0,0 +1,50 @@
+// This file is part of the `Selene` library.
+// Copyright 2017-2018 Michael Hofmann (https://github.com/kmhofmann).
+// Distributed under MIT license. See accompanying LICENSE file in the top-level directory.
+
+#include <selene/img/ImageToImageData.hpp>
+#include <selene/img_io/IO.hpp>
+#include <selene/img_ops/Algorithms.hpp>
+
+#include <selene/io/FileWriter.hpp>
+
+#include <iostream>
+#include <string>
+
+#include "Utils.hpp"
+
+constexpr auto output_filename_transformed = "bike_duck_transformed.png";
+
+using namespace sln;  // Never outside of example code
+
+int main(int argc, char** argv)
+{
+  // Read data path as optional command line argument
+  const char* data_path = (argc >= 2) ? argv[1] : nullptr;
+
+  // Read in the example image (check the implementation in Utils.hpp);
+  // `Pixel_8u3` designates 3 channels of unsigned 8-bit data for each pixel.
+
+  const auto img_rgb = sln_examples::read_example_image<Pixel_8u3>("bike_duck.png", data_path);
+
+  // Transform the image from 8-bit integral to 32-bit floating point type, and normalize values to be within (0...1)
+  std::cout << "Transforming the image from 8-bit integral to 32-bit floating point type (0...1)...\n";
+  auto img_f = sln::transform_pixels<sln::Pixel_32f3>(img_rgb, [](const auto& px) { return sln::Pixel_32f3(px) / 255.0; });
+
+  // Play around with the color channels
+  sln::for_each_pixel(img_f, [](auto& px) {
+    px[0] = std::pow(px[0], 0.1);
+    px[1] = std::pow(px[1], 0.8);
+    px[2] = std::pow(px[2], 0.3);
+  });
+
+  // Transform the image back to 8-bit integral representation (0...255)
+  auto img_transf = sln::transform_pixels<sln::Pixel_8u3>(img_f, [](const auto& px) { return sln::Pixel_8u3(px * 255.0); });
+
+  // Write out the transformed image to disk
+  std::cout << "Writing the result to disk: '" << output_filename_transformed << "'...\n";
+  write_image(to_image_data_view(img_transf, PixelFormat::RGB), ImageFormat::PNG,
+              FileWriter(output_filename_transformed));
+
+  return 0;
+}