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| 1 | +/* |
| 2 | +LodePNG Examples |
| 3 | +
|
| 4 | +Copyright (c) 2005-2010 Lode Vandevenne |
| 5 | +
|
| 6 | +This software is provided 'as-is', without any express or implied |
| 7 | +warranty. In no event will the authors be held liable for any damages |
| 8 | +arising from the use of this software. |
| 9 | +
|
| 10 | +Permission is granted to anyone to use this software for any purpose, |
| 11 | +including commercial applications, and to alter it and redistribute it |
| 12 | +freely, subject to the following restrictions: |
| 13 | +
|
| 14 | + 1. The origin of this software must not be misrepresented; you must not |
| 15 | + claim that you wrote the original software. If you use this software |
| 16 | + in a product, an acknowledgment in the product documentation would be |
| 17 | + appreciated but is not required. |
| 18 | +
|
| 19 | + 2. Altered source versions must be plainly marked as such, and must not be |
| 20 | + misrepresented as being the original software. |
| 21 | +
|
| 22 | + 3. This notice may not be removed or altered from any source |
| 23 | + distribution. |
| 24 | +*/ |
| 25 | + |
| 26 | +/* |
| 27 | +Load a BMP image and convert it to a PNG image. This example also shows how |
| 28 | +to use other data with the same memory structure as BMP, such as the image |
| 29 | +format native to win32, GDI (HBITMAP, BITMAPINFO, ...) often encountered if |
| 30 | +you're programming for Windows in Visual Studio. |
| 31 | +
|
| 32 | +This example only supports uncompressed 24-bit RGB or 32-bit RGBA bitmaps. |
| 33 | +For other types of BMP's, use a full fledged BMP decoder, or convert the |
| 34 | +bitmap to 24-bit or 32-bit format. |
| 35 | +
|
| 36 | +NOTE: it overwrites the output file without warning if it exists! |
| 37 | +*/ |
| 38 | + |
| 39 | +//g++ lodepng.cpp example_bmp2png.cpp -ansi -pedantic -Wall -Wextra -O3 |
| 40 | + |
| 41 | +#include "lodepng.h" |
| 42 | + |
| 43 | +#include <iostream> |
| 44 | + |
| 45 | +//returns 0 if all went ok, non-0 if error |
| 46 | +//output image is always given in RGBA (with alpha channel), even if it's a BMP without alpha channel |
| 47 | +unsigned decodeBMP(std::vector<unsigned char>& image, unsigned& w, unsigned& h, const std::vector<unsigned char>& bmp) { |
| 48 | + static const unsigned MINHEADER = 54; //minimum BMP header size |
| 49 | + |
| 50 | + if(bmp.size() < MINHEADER) return -1; |
| 51 | + if(bmp[0] != 'B' || bmp[1] != 'M') return 1; //It's not a BMP file if it doesn't start with marker 'BM' |
| 52 | + unsigned pixeloffset = bmp[10] + 256 * bmp[11]; //where the pixel data starts |
| 53 | + //read width and height from BMP header |
| 54 | + w = bmp[18] + bmp[19] * 256; |
| 55 | + h = bmp[22] + bmp[23] * 256; |
| 56 | + //read number of channels from BMP header |
| 57 | + if(bmp[28] != 24 && bmp[28] != 32) return 2; //only 24-bit and 32-bit BMPs are supported. |
| 58 | + unsigned numChannels = bmp[28] / 8; |
| 59 | + |
| 60 | + //The amount of scanline bytes is width of image times channels, with extra bytes added if needed |
| 61 | + //to make it a multiple of 4 bytes. |
| 62 | + unsigned scanlineBytes = w * numChannels; |
| 63 | + if(scanlineBytes % 4 != 0) scanlineBytes = (scanlineBytes / 4) * 4 + 4; |
| 64 | + |
| 65 | + unsigned dataSize = scanlineBytes * h; |
| 66 | + if(bmp.size() < dataSize + pixeloffset) return 3; //BMP file too small to contain all pixels |
| 67 | + |
| 68 | + image.resize(w * h * 4); |
| 69 | + |
| 70 | + /* |
| 71 | + There are 3 differences between BMP and the raw image buffer for LodePNG: |
| 72 | + -it's upside down |
| 73 | + -it's in BGR instead of RGB format (or BRGA instead of RGBA) |
| 74 | + -each scanline has padding bytes to make it a multiple of 4 if needed |
| 75 | + The 2D for loop below does all these 3 conversions at once. |
| 76 | + */ |
| 77 | + for(unsigned y = 0; y < h; y++) |
| 78 | + for(unsigned x = 0; x < w; x++) { |
| 79 | + //pixel start byte position in the BMP |
| 80 | + unsigned bmpos = pixeloffset + (h - y - 1) * scanlineBytes + numChannels * x; |
| 81 | + //pixel start byte position in the new raw image |
| 82 | + unsigned newpos = 4 * y * w + 4 * x; |
| 83 | + if(numChannels == 3) { |
| 84 | + image[newpos + 0] = bmp[bmpos + 2]; //R |
| 85 | + image[newpos + 1] = bmp[bmpos + 1]; //G |
| 86 | + image[newpos + 2] = bmp[bmpos + 0]; //B |
| 87 | + image[newpos + 3] = 255; //A |
| 88 | + } else { |
| 89 | + image[newpos + 0] = bmp[bmpos + 2]; //R |
| 90 | + image[newpos + 1] = bmp[bmpos + 1]; //G |
| 91 | + image[newpos + 2] = bmp[bmpos + 0]; //B |
| 92 | + image[newpos + 3] = bmp[bmpos + 3]; //A |
| 93 | + } |
| 94 | + } |
| 95 | + return 0; |
| 96 | +} |
| 97 | + |
| 98 | +int main(int argc, char *argv[]) { |
| 99 | + if(argc < 3) { |
| 100 | + std::cout << "Please provide input BMP and output PNG file names" << std::endl; |
| 101 | + return 0; |
| 102 | + } |
| 103 | + |
| 104 | + std::vector<unsigned char> bmp; |
| 105 | + lodepng::load_file(bmp, argv[1]); |
| 106 | + std::vector<unsigned char> image; |
| 107 | + unsigned w, h; |
| 108 | + unsigned error = decodeBMP(image, w, h, bmp); |
| 109 | + |
| 110 | + if(error) { |
| 111 | + std::cout << "BMP decoding error " << error << std::endl; |
| 112 | + return 0; |
| 113 | + } |
| 114 | + |
| 115 | + std::vector<unsigned char> png; |
| 116 | + error = lodepng::encode(png, image, w, h); |
| 117 | + |
| 118 | + if(error) { |
| 119 | + std::cout << "PNG encoding error " << error << ": " << lodepng_error_text(error) << std::endl; |
| 120 | + return 0; |
| 121 | + } |
| 122 | + |
| 123 | + lodepng::save_file(png, argv[2]); |
| 124 | + |
| 125 | +} |
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