[CPP Library] Enhanced support.

[dorpxam]

Hello, I would like to submit some modifications to you in order to optimize compatibility with the standard library and VS compilers.

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Compiling under Visual Studio 2022 with and without LLVM/Clang.

There's a missing include for the files:

cpp/temperature/temperature_cache.h(105,8): error : no template named 'optional' in namespace 'std'
cpp/temperature/temperature_cache.h(106,8): error : no template named 'optional' in namespace 'std'
cpp/temperature/temperature_cache.h(107,8): error : no template named 'optional' in namespace 'std'
cpp/temperature/temperature_cache.h(108,8): error : no template named 'optional' in namespace 'std'

Solution:

#include <optional>

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Here, it's the famous unix-style M_PI, not found in VS system:

cpp\dynamiccolor\material_dynamic_colors.cc(54,28): error : use of undeclared identifier 'M_PI'

Solution:

constexpr double M_PI = 3.141592653589793;

for WIN_32 defined system.

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Compiling under Visual Studio 2022 only, no error with LLVM/Clang.

cpp\cam\viewing_conditions.h(49,60): error C4576
cpp\cam\hct_solver.cc(220,10): error C4576:
cpp\cam\hct_solver.cc(279,14): error C4576:
cpp\cam\hct_solver.cc(281,14): error C4576:
cpp\cam\hct_solver.cc(288,14): error C4576:
cpp\cam\hct_solver.cc(290,14): error C4576:
cpp\cam\hct_solver.cc(297,14): error C4576:
cpp\cam\hct_solver.cc(299,14): error C4576:
cpp\cam\hct_solver.cc(313,15): error C4576:
cpp\cam\hct_solver.cc(349,10): error C4576:
cpp\cam\hct_solver.cc(459,19): error C4576:
cpp\utils\utils.cc(175,10): error C4576

Where error C4576 = a parenthesized type followed by an initializer list is a non-standard explicit type conversion syntax

Solution:

remove traditional style cast before initializer list, the conversion is implicit.

After changes

Build successfully done under internal VS2022 and LLVM/Clang compilers.

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About the Abseil Common Libraries dependency.

In 'utils.cc' and 'wsmeans.cc' there's dependencies over Abseil Common Libraries (C++).

A solution can be to make the Abseil library optional.

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The HexFromArgb function:

In 'utils.cc' we have a include #include "absl/strings/str_cat.h" for the hexadecimal int string formatting. Just replace the include by :

#ifdef USE_ABSEIL_LIBRARY
#include "absl/strings/str_cat.h"
#else
#include <sstream>
#include <iomanip>
#endif

and modify the function with this one:

std::string HexFromArgb(Argb argb) 
{
#ifdef USE_ABSEIL_LIBRARY
    return absl::StrCat(absl::Hex(argb));
#else
    std::stringstream stream;
    stream << std::hex << argb;
    return stream.str();
#endif
}

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The QuantizeWsmeans function:

In 'wsmeans.cc' we have a include #include "absl/container/flat_hash_map.h" for the better performance in the QuantizeWsmeans function. Just replace the include by :

#ifdef USE_ABSEIL_LIBRARY
#include "absl/container/flat_hash_map.h"
template <typename key, typename value>
using choiced_map = absl::flat_hash_map<key, value>;
#else
template <typename key, typename value>
using choiced_map = std::unordered_map<key, value>;
#endif

and modify the function with this one:

QuantizerResult QuantizeWsmeans(const std::vector<Argb>& input_pixels,
                                const std::vector<Argb>& starting_clusters,
                                uint16_t max_colors) {
  if (max_colors == 0 || input_pixels.empty()) {
    return QuantizerResult();
  }

  if (max_colors > 256) {
    // If colors is outside the range, just set it the max.
    max_colors = 256;
  }

  uint32_t pixel_count = input_pixels.size();
  choiced_map<Argb, int> pixel_to_count;
  std::vector<uint32_t> pixels;
  pixels.reserve(pixel_count);
  std::vector<Lab> points;
  points.reserve(pixel_count);
  for (Argb pixel : input_pixels) {
    // tested over 1000 runs with 128 colors, 12544 (112 x 112)
    // std::map 10.9 ms
    // std::unordered_map 10.2 ms
    // absl::btree_map 9.0 ms
    // absl::flat_hash_map 8.0 ms
    choiced_map<Argb, int>::iterator it = pixel_to_count.find(pixel);
    if (it != pixel_to_count.end()) {
      it->second++;

    } else {
      pixels.push_back(pixel);
      points.push_back(LabFromInt(pixel));
      pixel_to_count[pixel] = 1;
    }
  }

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Conclusion

Thank you very much for this great library and the whole Material Design project.