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123 lines
4.0 KiB
C++
123 lines
4.0 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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//Compile command for Linux:
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//g++ lodepng.cpp example_sdl.cpp -lSDL -O3 -o showpng
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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 SDL 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 <iostream>
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#include <SDL/SDL.h>
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int show(const std::string& caption, const unsigned char* rgba, unsigned w, unsigned h) {
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//avoid too large window size by downscaling large image
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unsigned jump = 1;
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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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//init SDL
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if(SDL_Init(SDL_INIT_VIDEO) < 0) {
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std::cout << "error, SDL video init failed" << std::endl;
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return 0;
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}
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SDL_Surface* scr = SDL_SetVideoMode(w / jump, h / jump, 32, SDL_HWSURFACE);
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if(!scr) {
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std::cout << "error, no SDL screen" << std::endl;
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return 0;
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}
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SDL_WM_SetCaption(caption.c_str(), NULL); //set window caption
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//plot the pixels of the PNG file
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for(unsigned y = 0; y + jump - 1 < h; y += jump)
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for(unsigned x = 0; x + jump - 1 < w; x += jump) {
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//get RGBA components
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Uint32 r = rgba[4 * y * w + 4 * x + 0]; //red
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Uint32 g = rgba[4 * y * w + 4 * x + 1]; //green
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Uint32 b = rgba[4 * y * w + 4 * x + 2]; //blue
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Uint32 a = rgba[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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Uint32* bufp;
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bufp = (Uint32 *)scr->pixels + (y * scr->pitch / 4) / jump + (x / jump);
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*bufp = 65536 * r + 256 * g + b;
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}
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//pause until you press escape and meanwhile redraw screen
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SDL_Event event;
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int done = 0;
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while(done == 0) {
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while(SDL_PollEvent(&event)) {
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if(event.type == SDL_QUIT) done = 2;
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else if(SDL_GetKeyState(NULL)[SDLK_ESCAPE]) done = 2;
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else if(event.type == SDL_KEYDOWN) done = 1; //press any other key for next image
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}
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SDL_UpdateRect(scr, 0, 0, 0, 0); //redraw screen
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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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return done == 2 ? 1 : 0;
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}
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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 showfile(const char* filename) {
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std::cout << "showing " << filename << std::endl;
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std::vector<unsigned char> buffer, image;
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lodepng::load_file(buffer, filename); //load the image file with given filename
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unsigned w, h;
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unsigned error = lodepng::decode(image, w, h, buffer); //decode the png
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//stop if there is an error
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if(error) {
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std::cout << "decoder error " << error << ": " << lodepng_error_text(error) << std::endl;
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return 0;
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}
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return show(filename, &image[0], w, h);
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}
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int main(int argc, char* argv[]) {
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if(argc <= 1) std::cout << "Please enter PNG file name(s) to display" << std::endl;
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for(int i = 1; i < argc; i++) {
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if(showfile(argv[i])) return 0;
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}
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}
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