add example and dev files to LodePNG repository

1 files changed, 132 insertions, 0 deletions

diff --git a/example_png2bmp.cpp b/example_png2bmp.cpp
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+/*
+LodePNG Examples
+
+Copyright (c) 2005-2012 Lode Vandevenne
+
+This software is provided 'as-is', without any express or implied
+warranty. In no event will the authors be held liable for any damages
+arising from the use of this software.
+
+Permission is granted to anyone to use this software for any purpose,
+including commercial applications, and to alter it and redistribute it
+freely, subject to the following restrictions:
+
+    1. The origin of this software must not be misrepresented; you must not
+    claim that you wrote the original software. If you use this software
+    in a product, an acknowledgment in the product documentation would be
+    appreciated but is not required.
+
+    2. Altered source versions must be plainly marked as such, and must not be
+    misrepresented as being the original software.
+
+    3. This notice may not be removed or altered from any source
+    distribution.
+*/
+
+#include "lodepng.h"
+#include <iostream>
+
+/*
+This example converts a PNG file to a BMP file.
+NOTE: it overwrites the output file without warning if it exists!
+Give the PNG and the BMP file names as command line arguments.
+*/
+
+/*
+g++ lodepng.cpp example_png2bmp.cpp -Wall -Wextra -pedantic -ansi -lSDL -O3
+*/
+
+
+
+//Input image must be RGB buffer (3 bytes per pixel), but you can easily make it
+//support RGBA input and output by changing the inputChannels and/or outputChannels
+//in the function to 4.
+void encodeBMP(std::vector<unsigned char>& bmp, const unsigned char* image, int w, int h)
+{
+  //3 bytes per pixel used for both input and output.
+  int inputChannels = 3;
+  int outputChannels = 3;
+  
+  //bytes 0-13
+  bmp.push_back('B'); bmp.push_back('M'); //0: bfType
+  bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); //2: bfSize; size not yet known for now, filled in later.
+  bmp.push_back(0); bmp.push_back(0); //6: bfReserved1
+  bmp.push_back(0); bmp.push_back(0); //8: bfReserved2
+  bmp.push_back(54 % 256); bmp.push_back(54 / 256); bmp.push_back(0); bmp.push_back(0); //10: bfOffBits (54 header bytes)
+
+  //bytes 14-53
+  bmp.push_back(40); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0);  //14: biSize
+  bmp.push_back(w % 256); bmp.push_back(w / 256); bmp.push_back(0); bmp.push_back(0); //18: biWidth
+  bmp.push_back(h % 256); bmp.push_back(h / 256); bmp.push_back(0); bmp.push_back(0); //22: biHeight
+  bmp.push_back(1); bmp.push_back(0); //26: biPlanes
+  bmp.push_back(outputChannels * 8); bmp.push_back(0); //28: biBitCount
+  bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0);  //30: biCompression
+  bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0);  //34: biSizeImage
+  bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0);  //38: biXPelsPerMeter
+  bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0);  //42: biYPelsPerMeter
+  bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0);  //46: biClrUsed
+  bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0);  //50: biClrImportant
+  
+  /*
+  Convert the input RGBRGBRGB pixel buffer to the BMP pixel buffer format. There are 3 differences with the input buffer:
+  -BMP stores the rows inversed, from bottom to top
+  -BMP stores the color channels in BGR instead of RGB order
+  -BMP requires each row to have a multiple of 4 bytes, so sometimes padding bytes are added between rows
+  */
+
+  int imagerowbytes = outputChannels * w;
+  imagerowbytes = imagerowbytes % 4 == 0 ? imagerowbytes : imagerowbytes + (4 - imagerowbytes % 4); //must be multiple of 4
+  
+  for(int y = h - 1; y >= 0; y--) //the rows are stored inversed in bmp
+  {
+    int c = 0;
+    for(int x = 0; x < imagerowbytes; x++)
+    {
+      if(x < w * outputChannels)
+      {
+        int inc = c;
+        //Convert RGB(A) into BGR(A)
+        if(c == 0) inc = 2;
+        else if(c == 2) inc = 0;
+        bmp.push_back(image[inputChannels * (w * y + x / outputChannels) + inc]);
+      }
+      else bmp.push_back(0);
+      c++;
+      if(c >= outputChannels) c = 0;
+    }
+  }
+
+  // Fill in the size
+  bmp[2] = bmp.size() % 256;
+  bmp[3] = (bmp.size() / 256) % 256;
+  bmp[4] = (bmp.size() / 65536) % 256;
+  bmp[5] = bmp.size() / 16777216;
+}
+
+int main(int argc, char *argv[])
+{
+  if(argc < 3)
+  {
+    std::cout << "Please provice input PNG and output BMP file names" << std::endl;
+    return 0;
+  }
+  const char* infile = argv[1];
+  const char* outfile = argv[2];
+  
+  
+  std::vector<unsigned char> image; //the raw pixels
+  unsigned width, height;
+
+  unsigned error = lodepng::decode(image, width, height, infile, LCT_RGB, 8);
+
+  if(error)
+  {
+    std::cout << "error " << error << ": " << lodepng_error_text(error) << std::endl;
+    return 0;
+  }
+
+  std::vector<unsigned char> bmp;
+  encodeBMP(bmp, &image[0], width, height);
+  
+  lodepng::save_file(bmp, outfile);
+}