143 lines
4.4 KiB
C
143 lines
4.4 KiB
C
/*
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LodePNG Examples
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Copyright (c) 2005-2012 Lode Vandevenne
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source
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distribution.
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*/
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/*
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Compile command for Linux:
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gcc lodepng.c example_sdl.c -ansi -pedantic -Wall -Wextra -lSDL2 -O3 -o showpng
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*/
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/*
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LodePNG SDL example
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This example displays a PNG with a checkerboard pattern to show tranparency.
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It requires the SDL2 library to compile and run.
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If multiple filenames are given to the command line, it shows all of them.
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Press any key to see next image, or esc to quit.
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*/
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#include "lodepng.h"
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#include <SDL2/SDL.h>
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/*shows image with SDL. Returns 1 if user wants to fully quit, 0 if user wants to see next image.*/
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int show(const char* filename) {
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unsigned error;
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unsigned char* image;
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unsigned w, h, x, y;
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int done;
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size_t jump = 1;
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SDL_Window* sdl_window;
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SDL_Renderer* sdl_renderer;
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SDL_Texture* sdl_texture;
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SDL_Event sdl_event;
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size_t screenw, screenh, pitch;
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Uint32* sdl_pixels;
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printf("showing %s\n", filename);
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/*load the PNG in one function call*/
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error = lodepng_decode32_file(&image, &w, &h, filename);
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/*stop if there is an error*/
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if(error) {
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printf("decoder error %u: %s\n", error, lodepng_error_text(error));
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return 0;
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}
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/* avoid too large window size by downscaling large image */
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if(w / 1024 >= jump) jump = w / 1024 + 1;
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if(h / 1024 >= jump) jump = h / 1024 + 1;
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screenw = w / jump;
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screenh = h / jump;
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pitch = screenw * sizeof(Uint32);
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/* init SDL */
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SDL_CreateWindowAndRenderer(screenw, screenh, SDL_WINDOW_OPENGL, &sdl_window, &sdl_renderer);
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SDL_SetWindowTitle(sdl_window, filename);
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if(!sdl_window) {
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printf("Error, no SDL screen\n");
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return 0;
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}
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sdl_texture = SDL_CreateTexture(sdl_renderer, SDL_PIXELFORMAT_ARGB8888,
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SDL_TEXTUREACCESS_STREAMING, screenw, screenh);
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sdl_pixels = (Uint32*)malloc(screenw * screenh * sizeof(Uint32));
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if(!sdl_pixels) {
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printf("Failed to allocate pixels\n");
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return 0;
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}
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/* plot the pixels of the PNG file */
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for(y = 0; y + jump - 1 < h; y += jump)
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for(x = 0; x + jump - 1 < w; x += jump) {
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/* get RGBA components */
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Uint32 r = image[4 * y * w + 4 * x + 0]; /* red */
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Uint32 g = image[4 * y * w + 4 * x + 1]; /* green */
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Uint32 b = image[4 * y * w + 4 * x + 2]; /* blue */
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Uint32 a = image[4 * y * w + 4 * x + 3]; /* alpha */
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/* make translucency visible by placing checkerboard pattern behind image */
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int checkerColor = 191 + 64 * (((x / 16) % 2) == ((y / 16) % 2));
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r = (a * r + (255 - a) * checkerColor) / 255;
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g = (a * g + (255 - a) * checkerColor) / 255;
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b = (a * b + (255 - a) * checkerColor) / 255;
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/* give the color value to the pixel of the screenbuffer */
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sdl_pixels[(y * screenw + x) / jump] = 65536 * r + 256 * g + b;
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}
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/* render the pixels to the screen */
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SDL_UpdateTexture(sdl_texture, NULL, sdl_pixels, pitch);
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SDL_RenderClear(sdl_renderer);
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SDL_RenderCopy(sdl_renderer, sdl_texture, NULL, NULL);
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SDL_RenderPresent(sdl_renderer);
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/* pause until you press escape and meanwhile redraw screen */
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done = 0;
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while(done == 0) {
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while(SDL_PollEvent(&sdl_event)) {
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if(sdl_event.type == SDL_QUIT) done = 2;
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else if(SDL_GetKeyboardState(NULL)[SDLK_ESCAPE]) done = 2;
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else if(sdl_event.type == SDL_KEYDOWN) done = 1; /* press any other key for next image */
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}
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SDL_Delay(5); /* pause 5 ms so it consumes less processing power */
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}
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SDL_Quit();
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free(sdl_pixels);
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return done == 2 ? 1 : 0;
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}
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int main(int argc, char* argv[]) {
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int i;
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if(argc <= 1) printf("Please enter PNG file name(s) to display\n");;
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for(i = 1; i < argc; i++) {
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if(show(argv[i])) return 0;
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}
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return 0;
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}
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