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126 lines
4.7 KiB
C++
126 lines
4.7 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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#include "lodepng.h"
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#include <iostream>
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/*
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This example converts a PNG file to a BMP file.
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NOTE: it overwrites the output file without warning if it exists!
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Give the PNG and the BMP file names as command line arguments.
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*/
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/*
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g++ lodepng.cpp example_png2bmp.cpp -Wall -Wextra -pedantic -ansi -lSDL -O3
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*/
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//Input image must be RGB buffer (3 bytes per pixel), but you can easily make it
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//support RGBA input and output by changing the inputChannels and/or outputChannels
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//in the function to 4.
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void encodeBMP(std::vector<unsigned char>& bmp, const unsigned char* image, int w, int h) {
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//3 bytes per pixel used for both input and output.
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int inputChannels = 3;
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int outputChannels = 3;
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//bytes 0-13
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bmp.push_back('B'); bmp.push_back('M'); //0: bfType
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bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); //2: bfSize; size not yet known for now, filled in later.
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bmp.push_back(0); bmp.push_back(0); //6: bfReserved1
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bmp.push_back(0); bmp.push_back(0); //8: bfReserved2
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bmp.push_back(54 % 256); bmp.push_back(54 / 256); bmp.push_back(0); bmp.push_back(0); //10: bfOffBits (54 header bytes)
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//bytes 14-53
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bmp.push_back(40); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); //14: biSize
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bmp.push_back(w % 256); bmp.push_back(w / 256); bmp.push_back(0); bmp.push_back(0); //18: biWidth
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bmp.push_back(h % 256); bmp.push_back(h / 256); bmp.push_back(0); bmp.push_back(0); //22: biHeight
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bmp.push_back(1); bmp.push_back(0); //26: biPlanes
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bmp.push_back(outputChannels * 8); bmp.push_back(0); //28: biBitCount
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bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); //30: biCompression
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bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); //34: biSizeImage
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bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); //38: biXPelsPerMeter
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bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); //42: biYPelsPerMeter
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bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); //46: biClrUsed
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bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); bmp.push_back(0); //50: biClrImportant
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/*
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Convert the input RGBRGBRGB pixel buffer to the BMP pixel buffer format. There are 3 differences with the input buffer:
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-BMP stores the rows inversed, from bottom to top
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-BMP stores the color channels in BGR instead of RGB order
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-BMP requires each row to have a multiple of 4 bytes, so sometimes padding bytes are added between rows
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*/
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int imagerowbytes = outputChannels * w;
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imagerowbytes = imagerowbytes % 4 == 0 ? imagerowbytes : imagerowbytes + (4 - imagerowbytes % 4); //must be multiple of 4
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for(int y = h - 1; y >= 0; y--) { //the rows are stored inversed in bmp
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int c = 0;
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for(int x = 0; x < imagerowbytes; x++) {
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if(x < w * outputChannels) {
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int inc = c;
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//Convert RGB(A) into BGR(A)
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if(c == 0) inc = 2;
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else if(c == 2) inc = 0;
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bmp.push_back(image[inputChannels * (w * y + x / outputChannels) + inc]);
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}
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else bmp.push_back(0);
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c++;
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if(c >= outputChannels) c = 0;
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}
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}
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// Fill in the size
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bmp[2] = bmp.size() % 256;
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bmp[3] = (bmp.size() / 256) % 256;
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bmp[4] = (bmp.size() / 65536) % 256;
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bmp[5] = bmp.size() / 16777216;
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}
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int main(int argc, char *argv[]) {
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if(argc < 3) {
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std::cout << "Please provice input PNG and output BMP file names" << std::endl;
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return 0;
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}
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const char* infile = argv[1];
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const char* outfile = argv[2];
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std::vector<unsigned char> image; //the raw pixels
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unsigned width, height;
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unsigned error = lodepng::decode(image, width, height, infile, LCT_RGB, 8);
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if(error) {
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std::cout << "error " << error << ": " << lodepng_error_text(error) << std::endl;
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return 0;
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}
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std::vector<unsigned char> bmp;
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encodeBMP(bmp, &image[0], width, height);
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lodepng::save_file(bmp, outfile);
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}
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