add example and dev files to LodePNG repository

1 files changed, 132 insertions, 0 deletions

diff --git a/example_sdl.cpp b/example_sdl.cpp
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+++ b/example_sdl.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.
+*/
+
+//Compile command for Linux:
+//g++ lodepng.cpp example_sdl.cpp -lSDL -O3 -o showpng
+
+/*
+LodePNG SDL example
+This example displays a PNG with a checkerboard pattern to show tranparency.
+It requires the SDL library to compile and run.
+If multiple filenames are given to the command line, it shows all of them.
+Press any key to see next image, or esc to quit.
+*/
+
+#include "lodepng.h"
+
+#include <iostream>
+#include <SDL/SDL.h>
+
+int show(const std::string& caption, const unsigned char* rgba, unsigned w, unsigned h)
+{
+  //avoid too large window size by downscaling large image
+  unsigned jump = 1;
+  if(w / 1024 >= jump) jump = w / 1024 + 1;
+  if(h / 1024 >= jump) jump = h / 1024 + 1;
+
+  //init SDL
+  if(SDL_Init(SDL_INIT_VIDEO) < 0)
+  {
+    std::cout << "error, SDL video init failed" << std::endl;
+    return 0;
+  }
+  SDL_Surface* scr = SDL_SetVideoMode(w / jump, h / jump, 32, SDL_HWSURFACE);
+  if(!scr)
+  {
+    std::cout << "error, no SDL screen" << std::endl;
+    return 0;
+  }
+  SDL_WM_SetCaption(caption.c_str(), NULL); //set window caption
+
+  //plot the pixels of the PNG file
+  for(unsigned y = 0; y + jump - 1 < h; y += jump)
+  for(unsigned x = 0; x + jump - 1 < w; x += jump)
+  {
+    //get RGBA components
+    Uint32 r = rgba[4 * y * w + 4 * x + 0]; //red
+    Uint32 g = rgba[4 * y * w + 4 * x + 1]; //green
+    Uint32 b = rgba[4 * y * w + 4 * x + 2]; //blue
+    Uint32 a = rgba[4 * y * w + 4 * x + 3]; //alpha
+
+    //make translucency visible by placing checkerboard pattern behind image
+    int checkerColor = 191 + 64 * (((x / 16) % 2) == ((y / 16) % 2));
+    r = (a * r + (255 - a) * checkerColor) / 255;
+    g = (a * g + (255 - a) * checkerColor) / 255;
+    b = (a * b + (255 - a) * checkerColor) / 255;
+
+    //give the color value to the pixel of the screenbuffer
+    Uint32* bufp;
+    bufp = (Uint32 *)scr->pixels + (y * scr->pitch / 4) / jump + (x / jump);
+    *bufp = 65536 * r + 256 * g + b;
+  }
+
+  //pause until you press escape and meanwhile redraw screen
+  SDL_Event event;
+  int done = 0;
+  while(done == 0)
+  {
+    while(SDL_PollEvent(&event))
+    {
+      if(event.type == SDL_QUIT) done = 2;
+      else if(SDL_GetKeyState(NULL)[SDLK_ESCAPE]) done = 2;
+      else if(event.type == SDL_KEYDOWN) done = 1; //press any other key for next image
+    }
+    SDL_UpdateRect(scr, 0, 0, 0, 0); //redraw screen
+    SDL_Delay(5); //pause 5 ms so it consumes less processing power
+  }
+
+  SDL_Quit();
+  return done == 2 ? 1 : 0;
+}
+
+/*shows image with SDL. Returns 1 if user wants to fully quit, 0 if user wants to see next image.*/
+int showfile(const char* filename)
+{
+  std::cout << "showing " << filename << std::endl;
+
+  std::vector<unsigned char> buffer, image;
+  lodepng::load_file(buffer, filename); //load the image file with given filename
+  unsigned w, h;
+  unsigned error = lodepng::decode(image, w, h, buffer); //decode the png
+
+  //stop if there is an error
+  if(error)
+  {
+    std::cout << "decoder error " << error << ": " << lodepng_error_text(error) << std::endl;
+    return 0;
+  }
+
+  return show(filename, &image[0], w, h);
+}
+
+int main(int argc, char* argv[])
+{
+  if(argc <= 1) std::cout << "Please enter PNG file name(s) to display" << std::endl;
+
+  for(int i = 1; i < argc; i++)
+  {
+    if(showfile(argv[i])) return 0;
+  }
+}