feat: add ostream support.

Author: caozhanhao

README.md

@@ -71,18 +71,22 @@ qr.disable_quiet_zone();
 - PNG
 - TGA
 - BMP
+- ANSI
 
-##### paint(format, filename, enlarge)
+##### paint(format, filename/ostream, enlarge)
 
 - the image size = dimension * enlarge x dimension * enlarge
 
-##### paint(format, filename, width, height)
+##### paint(format, filename/ostream, width, height)
 
 - the image size = width x height
 
 ```c++
-qr.generate().paint(pic::Format::BMP, "example.bmp", 10);
-qr.generate().paint(pic::Format::PNG, "example.bmp", 1024, 1024);
+auto pic = qr.generate();
+pic.paint(pic::Format::BMP, "example.bmp", 10);
+std::ofstream fs("examples/example2.png", std::ios::binary | std::ios::out);
+pic.paint(pic::Format::PNG, fs, 1024, 1024);
+fs.close();
 ```
 
 For more examples, see [here](examples/src/main.cpp)

examples/src/main.cpp

@@ -55,11 +55,13 @@ int main()
    *  Output
    */
   //             func                                           output pic
-  // - paint(fmt, path, enlarge)         -> (QR dimension * enlarge) * (QR dimension * enlarge)
-  // - paint(fmt, path, width, height)   -> width * height
+  // - paint(fmt, path/ostream, enlarge)         -> (QR dimension * enlarge) * (QR dimension * enlarge)
+  // - paint(fmt, path/ostream, width, height)   -> width * height
   // 1 PNG
   qr1.generate().paint(pic::Format::PNG, "examples/example1.png", 10);
-  qr2.generate().paint(pic::Format::PNG, "examples/example2.png", 100);
+  std::ofstream fs("examples/example2.png", std::ios::binary | std::ios::out);
+  qr2.generate().paint(pic::Format::PNG, fs, 100);
+  fs.close();
   // 2 JPG
   auto qr = qr3.generate();
   qr.paint(pic::Format::JPG, "examples/example3.jpg", 512, 512);

include/opqr/oppic.hpp

@@ -17,7 +17,9 @@
 #include "operror.hpp"
 
 #define STB_IMAGE_IMPLEMENTATION
-//#define STBI_ONLY_PNM
+#define STBI_ONLY_PNM
+#define STBI_ONLY_PNG
+
 #include "stb/stb_image.h"
 
 #define STB_IMAGE_WRITE_IMPLEMENTATION
@@ -50,12 +52,26 @@ namespace opqr::pic
     };
   private:
     std::vector<std::vector<bool>> data;
-  
+
   public:
     Pic(std::vector<std::vector<bool>> data_)
         : data(std::move(data_)) {}
-    
+  
     void paint(Format fmt, const std::string &path, size_t width, size_t height) const
+    {
+      std::ofstream fs(path, std::ios::binary | std::ios::out);
+      paint(fmt, fs, width, height);
+      fs.close();
+    }
+  
+    void paint(Format fmt, const std::string &path, size_t enlarge) const
+    {
+      std::ofstream fs(path, std::ios::binary | std::ios::out);
+      paint(fmt, fs, enlarge);
+      fs.close();
+    }
+  
+    void paint(Format fmt, std::ostream &os, size_t width, size_t height) const
     {
       if (fmt == Format::ANSI256)
       {
@@ -75,25 +91,10 @@ namespace opqr::pic
       pic.data = out;
       pic.width = static_cast<int>(width);
       pic.height = static_cast<int>(height);
-      write_pic(fmt, path, pic);
+      write_pic(fmt, os, pic);
       stbi_image_free(out);
     }
 
-    void paint(Format fmt, const std::string &path, size_t enlarge = 1) const
-    {
-      if (enlarge == 0)
-      {
-        throw error::Error(OPQR_ERROR_LOCATION, __func__, "enlarge must >= 1.");
-      }
-      if (fmt == Format::ANSI256)
-      {
-        throw error::Error(OPQR_ERROR_LOCATION, __func__, "Unsupported format(ANSI256) when writing to path");
-      }
-      auto pic = load_pic(enlarge);
-      write_pic(fmt, path, pic);
-      stbi_image_free(pic.data);
-    }
-  
     void paint(Format fmt, std::ostream &os, size_t enlarge = 1) const
     {
       if (enlarge == 0)
@@ -126,28 +127,37 @@ namespace opqr::pic
           }
           break;
         default:
-          throw error::Error(OPQR_ERROR_LOCATION, __func__, "Unsupported format when writing to a stream");
+        {
+          auto pic = load_pic(enlarge);
+          write_pic(fmt, os, pic);
+          stbi_image_free(pic.data);
+        }
           break;
       }
     }
 
   private:
-    void write_pic(Format fmt, const std::string &path, StbData data) const
+    void write_pic(Format fmt, std::ostream &os, StbData data) const
     {
       int ret = 0;
+      auto func = [](void *context, void *data, int size)
+      {
+        auto osptr = reinterpret_cast<std::ostream *>(context);
+        osptr->write(reinterpret_cast<char *>(data), size);
+      };
       switch (fmt)
       {
         case Format::JPG:
-          ret = stbi_write_jpg(path.c_str(), data.width, data.height, data.channels, data.data, 100);
+          ret = stbi_write_jpg_to_func(func, &os, data.width, data.height, data.channels, data.data, 100);
           break;
         case Format::PNG:
-          ret = stbi_write_png(path.c_str(), data.width, data.height, data.channels, data.data, 0);
+          ret = stbi_write_png_to_func(func, &os, data.width, data.height, data.channels, data.data, 0);
           break;
         case Format::TGA:
-          ret = stbi_write_tga(path.c_str(), data.width, data.height, data.channels, data.data);
+          ret = stbi_write_tga_to_func(func, &os, data.width, data.height, data.channels, data.data);
           break;
         case Format::BMP:
-          ret = stbi_write_bmp(path.c_str(), data.width, data.height, data.channels, data.data);
+          ret = stbi_write_bmp_to_func(func, &os, data.width, data.height, data.channels, data.data);
           break;
       }
       if (ret == 0)