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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:
+gcc lodepng.c example_sdl.c -ansi -pedantic -Wall -Wextra -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 <SDL/SDL.h>
+
+/*shows image with SDL. Returns 1 if user wants to fully quit, 0 if user wants to see next image.*/
+int show(const char* filename)
+{
+ unsigned error;
+ unsigned char* image;
+ unsigned w, h, x, y;
+ SDL_Surface* scr;
+ SDL_Event event;
+ int done;
+ size_t jump = 1;
+
+ printf("showing %s\n", filename);
+
+ /*load the PNG in one function call*/
+ error = lodepng_decode32_file(&image, &w, &h, filename);
+
+ /*stop if there is an error*/
+ if(error)
+ {
+ printf("decoder error %u: %s\n", error, lodepng_error_text(error));
+ return 0;
+ }
+
+ /*avoid too large window size by downscaling large image*/
+
+ 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)
+ {
+ printf("Error, SDL video init failed\n");
+ return 0;
+ }
+ scr = SDL_SetVideoMode(w / jump, h / jump, 32, SDL_HWSURFACE);
+ if(!scr)
+ {
+ printf("Error, no SDL screen\n");
+ return 0;
+ }
+ SDL_WM_SetCaption(filename, NULL); /*set window caption*/
+
+ /*plot the pixels of the PNG file*/
+ for(y = 0; y + jump - 1 < h; y += jump)
+ for(x = 0; x + jump - 1 < w; x += jump)
+ {
+ int checkerColor;
+ Uint32* bufp;
+ Uint32 r, g, b, a;
+
+ /*get RGBA components*/
+ r = image[4 * y * w + 4 * x + 0]; /*red*/
+ g = image[4 * y * w + 4 * x + 1]; /*green*/
+ b = image[4 * y * w + 4 * x + 2]; /*blue*/
+ a = image[4 * y * w + 4 * x + 3]; /*alpha*/
+
+ /*make translucency visible by placing checkerboard pattern behind image*/
+ 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*/
+ 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*/
+ 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*/
+ }
+
+ /*cleanup*/
+ free(image);
+ SDL_Quit();
+ return done == 2 ? 1 : 0;
+}
+
+int main(int argc, char* argv[])
+{
+ int i;
+
+ if(argc <= 1) printf("Please enter PNG file name(s) to display\n");;
+
+ for(i = 1; i < argc; i++)
+ {
+ if(show(argv[i])) return 0;
+ }
+ return 0;
+}