#define TINYEXR_IMPLEMENTATION
#include "tinyexr.h"

#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Weverything"
#endif

#define STB_IMAGE_RESIZE_IMPLEMENTATION
#include "stb_image_resize.h"

#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb_image_write.h"

#include "cxxopts.hpp"

#ifdef __clang__
#pragma clang diagnostic pop
#endif

namespace {

static void vnormalize(float v[3]) {
 const float d2 = v[0] * v[0] + v[1] * v[1] + v[2] * v[2];
 if (d2 > 1.0e-6f) {
   const float inv_d = 1.0f / std::sqrt(d2);
   v[0] *= inv_d;
   v[1] *= inv_d;
   v[2] *= inv_d;
 }
 return;
}


template<typename T>
static inline T clamp(const T v, const T min_v, const T max_v)
{
 return std::max(min_v, std::min(max_v, v));
}

//
// Compute gradient from scalar field.
// dx = (x + 1, y    ) - (x, y)
// dy = (x    , y + 1) - (x, y)
//
// TODO(syoyo): Use central difference with texel filtering.
//
static void Gradient(
 const std::vector<float> &src,
 const size_t width,
 const size_t height,
 const size_t x, const size_t y,
 const float bumpness,
 float dir[3])
{
 const size_t x1 = clamp(x + 1, size_t(0), width - 1);
 const size_t y1 = clamp(y + 1, size_t(0), height - 1);


 float v00 = src[y * width + x];
 float v01 = src[y * width + x1];
 float v11 = src[y1 * width + x];


 float dx = bumpness * (v01 - v00);
 float dy = bumpness * (v11 - v00);

 dir[0] = dx;
 dir[1] = dy;
 dir[2] = 0.0f;

}

///
/// Convert image(bump map for single channel, vector displacement map for 3 channels input) to normal map.
/// @param[in] base Base value fo
///
///
static void ToNormalMap(
 const std::vector<float> &src,
 const size_t width,
 const size_t height,
 const size_t channels,
 const float strength,
 std::vector<float> *dst)
{
 assert((channels == 1) || (channels == 3) || (channels == 4));

 dst->resize(width * height * 3);

 if (channels == 1) {
   // bump map
   for (size_t y = 0; y < height; y++) {
     for (size_t x = 0; x < width; x++) {
       float d[3];
       Gradient(src, width, height, x, y, strength, d);

       (*dst)[3 * (y * width + x) + 0] = d[0];
       (*dst)[3 * (y * width + x) + 1] = d[1];
       (*dst)[3 * (y * width + x) + 2] = d[2];

     }
   }

 } else {
   // vector displacement map

   for (size_t y = 0; y < height; y++) {
     for (size_t x = 0; x < width; x++) {

       float v[3];
       v[0] = src[channels * (y * width + x) + 0];
       v[1] = src[channels * (y * width + x) + 1];
       v[2] = src[channels * (y * width + x) + 2];

       v[0] *= strength;
       v[1] *= strength;
       v[2] *= strength;

       // Add (0, 0, 1)
       v[2] += 1.0f;

       // TODO(syoyo): Add option to not normalize.
       vnormalize(v);

       (*dst)[3 * (y * width + x) + 0] = 0.5f * v[0] + 0.5f;
       (*dst)[3 * (y * width + x) + 1] = 0.5f * v[1] + 0.5f;
       (*dst)[3 * (y * width + x) + 2] = 0.5f * v[2] + 0.5f;

     }
   }

 }

}

inline unsigned char ftouc(float f)
{
 int i = static_cast<int>(f * 255.0f);
 if (i > 255) i = 255;
 if (i < 0) i = 0;

 return static_cast<unsigned char>(i);
}

bool SaveImage(const char* filename, const float* rgb, int width, int height) {

 std::vector<unsigned char> dst(width * height * 3);

 for (size_t i = 0; i < width * height; i++) {
     dst[i * 3 + 0] = ftouc(rgb[i * 3 + 0]);
     dst[i * 3 + 1] = ftouc(rgb[i * 3 + 1]);
     dst[i * 3 + 2] = ftouc(rgb[i * 3 + 2]);
 }

 int ret = stbi_write_png(filename, width, height, 3, static_cast<const void*>(dst.data()), width * 3);

 return (ret > 0);
}

std::string GetFileExtension(const std::string &filename) {
 if (filename.find_last_of(".") != std::string::npos)
   return filename.substr(filename.find_last_of(".") + 1);
 return "";
}

} // namespace

int main(int argc, char **argv)
{
 cxxopts::Options options("normalmap", "help");
 options.add_options()
   ("s,strength", "Strength(scaling) for normal value", cxxopts::value<float>())
   ("i,input", "Input filename", cxxopts::value<std::string>())
   ("o,output", "Output filename", cxxopts::value<std::string>())
   ("r,resize", "Resize image. 0.5 = 50%%, 0.1 = 10%%", cxxopts::value<float>())
   ;

 auto result = options.parse(argc, argv);

 if (result.count("input") == 0) {
   std::cerr << "input filename missing" << std::endl;
   return EXIT_FAILURE;
 }

 if (result.count("output") == 0) {
   std::cerr << "output filename missing" << std::endl;
   return EXIT_FAILURE;
 }

 float strength = 1.0f;
 if (result.count("strength")) {
   strength = result["strength"].as<float>();
 }

 float resize = 1.0f;
 if (result.count("resize")) {
   resize = result["resize"].as<float>();
 }

 std::string input_filename = result["input"].as<std::string>();
 std::string output_filename = result["output"].as<std::string>();

 std::vector<float> src;
 size_t src_width;
 size_t src_height;

 {
   float *rgba = nullptr;
   int width, height;
   const char *err = nullptr;
   int ret = LoadEXR(&rgba, &width, &height, input_filename.c_str(), &err);
   if (TINYEXR_SUCCESS != ret) {
     std::cerr << "Failed to load EXR file [" << input_filename << "] code = " << ret << std::endl;
     if (err) {
       std::cerr << err << std::endl;
       FreeEXRErrorMessage(err);
     }

     return EXIT_FAILURE;
   }

   std::cout << "loaded EXR. width x height = " << width << "x" << height << std::endl;
   src.resize(size_t(width * height * 3));

   // ignore alpha for now
   for (size_t i = 0; i < size_t(width * height); i++) {
     src[3 * i + 0] = rgba[4 * i + 0];
     src[3 * i + 1] = rgba[4 * i + 1];
     src[3 * i + 2] = rgba[4 * i + 2];
   }

   src_width  = size_t(width);
   src_height = size_t(height);

   free(rgba);
 }

 std::cout << "strength = " << strength << std::endl;

 std::vector<float> dst;
 ToNormalMap(src, src_width, src_height, 3, strength, &dst);


 std::string ext = GetFileExtension(output_filename);
 if ((ext.compare("png") == 0) ||
     (ext.compare("PNG") == 0)) {
   // Save as LDR image.
   // Do not apply sRGB conversion for PNG(LDR) image.
   if (!SaveImage(output_filename.c_str(), dst.data(), int(src_width), int(src_height))) {
     std::cerr << "Failed to write a file : " << output_filename << std::endl;
     return EXIT_FAILURE;
   }
 } else {
   // assume EXR.
   float *rgba = nullptr;
   int width, height;
   int ret = SaveEXR(dst.data(), int(src_width), int(src_height), /* component */3, /* fp16 */0, output_filename.c_str(), nullptr);
   if (TINYEXR_SUCCESS != ret) {
     std::cerr << "Failed to save EXR file [" << input_filename << "] code = " << ret << std::endl;
     return EXIT_FAILURE;
   }
 }

 return EXIT_SUCCESS;
}

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