C ++从数组值中快速保存图像的方法 [英] C++ fast way to save image from array of values

问题描述

现在，我正在使用CImg。
由于这个问题我无法使用OpenCV 。

Right now, I am using CImg. I am unable to use OpenCV due to this issue.

我的CImg代码如下所示：

My CImg code looks like this:

cimg_library::CImg<float> img(512,512); 
cimg_forXYC(img,x,y,c) { img(x,y,c) = (array[x][y]); } //array contains all float values between 0/1
img.save(save.c_str()); //taking a  lot of time

通过使用时钟，我能够确定第一步，即for循环需要0-0.01秒。但是，第二步，即保存图像，需要0.06秒，由于我拥有的图像数量太长，这样做太长了。

By using clocks I was able to determine that the first step, the for loop takes 0-0.01 seconds. However, the second step, the saving of the image, takes 0.06 seconds, which is way too long due to the amount of images I have.

我保存为位图。
有没有更快的方法在C ++中完成相同的事情（从值数组创建图像并保存）？

I am saving as bitmaps. Is there any faster way to accomplish the same things (creating an image from an array of values and save) in C++?

推荐答案

这是一个小功能，可以用 pgm格式保存您的图像，大多数事情都可以阅读，并且很简单。它需要你的编译器支持C ++ 11，大多数都支持。它也被硬编码为512x512图像。

Here is a small function that will save your image in pgm format, which most things can read and is dead simple. It requires your compiler support C++11, which most do. It's also hard-coded to 512x512 images.

#include <fstream>
#include <string>
#include <cmath>
#include <cstdint>

void save_image(const ::std::string &name, float img_vals[][512])
{
   using ::std::string;
   using ::std::ios;
   using ::std::ofstream;
   typedef unsigned char pixval_t;
   auto float_to_pixval = [](float img_val) -> pixval_t {
      int tmpval = static_cast<int>(::std::floor(256 * img_val));
      if (tmpval < 0) {
         return 0u;
      } else if (tmpval > 255) {
         return 255u;
      } else {
         return tmpval & 0xffu;
      }
   };
   auto as_pgm = [](const string &name) -> string {
      if (! ((name.length() >= 4)
             && (name.substr(name.length() - 4, 4) == ".pgm")))
      {
         return name + ".pgm";
      } else {
         return name;
      }
   };

   ofstream out(as_pgm(name), ios::binary | ios::out | ios::trunc);

   out << "P5\n512 512\n255\n";
   for (int x = 0; x < 512; ++x) {
      for (int y = 0; y < 512; ++y) {
         const pixval_t pixval = float_to_pixval(img_vals[x][y]);
         const char outpv = static_cast<const char>(pixval);
         out.write(&outpv, 1);
      }
   }
}

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