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Diffstat (limited to 'examples/example_sdl.c')
-rw-r--r-- | examples/example_sdl.c | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/examples/example_sdl.c b/examples/example_sdl.c new file mode 100644 index 0000000..e4ae3de --- /dev/null +++ b/examples/example_sdl.c @@ -0,0 +1,142 @@ +/* +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; +} |