Add ktx

ktx/external/lodepng/examples/example_4bit_palette.cpp

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+/*
+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.
+*/
+
+//g++ lodepng.cpp example_4bit_palette.cpp -ansi -pedantic -Wall -Wextra -O3
+
+
+
+/*
+LodePNG 4-bit palette example.
+This example encodes a 511x511 PNG with a 4-bit palette.
+Both image and palette contain sine waves, resulting in a sort of plasma.
+The 511 (rather than power of two 512) size is of course chosen on purpose to
+confirm that scanlines not filling up an entire byte size are working.
+
+NOTE: a PNG image with a translucent palette is perfectly valid. However there
+exist some programs that cannot correctly read those, including, surprisingly,
+Gimp 2.8 image editor (until you set mode to RGB).
+*/
+
+#include <cmath>
+#include <iostream>
+
+#include "lodepng.h"
+
+int main(int argc, char *argv[]) {
+  //check if user gave a filename
+  if(argc < 2) {
+    std::cout << "please provide a filename to save to" << std::endl;
+    return 0;
+  }
+
+  //create encoder and set settings and info (optional)
+  lodepng::State state;
+
+  //generate palette
+  for(int i = 0; i < 16; i++) {
+    unsigned char r = 127 * (1 + std::sin(5 * i * 6.28318531 / 16));
+    unsigned char g = 127 * (1 + std::sin(2 * i * 6.28318531 / 16));
+    unsigned char b = 127 * (1 + std::sin(3 * i * 6.28318531 / 16));
+    unsigned char a = 63 * (1 + std::sin(8 * i * 6.28318531 / 16)) + 128; /*alpha channel of the palette (tRNS chunk)*/
+
+    //palette must be added both to input and output color mode, because in this
+    //sample both the raw image and the expected PNG image use that palette.
+    lodepng_palette_add(&state.info_png.color, r, g, b, a);
+    lodepng_palette_add(&state.info_raw, r, g, b, a);
+  }
+
+  //both the raw image and the encoded image must get colorType 3 (palette)
+  state.info_png.color.colortype = LCT_PALETTE; //if you comment this line, and create the above palette in info_raw instead, then you get the same image in a RGBA PNG.
+  state.info_png.color.bitdepth = 4;
+  state.info_raw.colortype = LCT_PALETTE;
+  state.info_raw.bitdepth = 4;
+  state.encoder.auto_convert = 0; //we specify ourselves exactly what output PNG color mode we want
+
+  //generate some image
+  const unsigned w = 511;
+  const unsigned h = 511;
+  std::vector<unsigned char> image;
+  image.resize((w * h * 4 + 7) / 8, 0);
+  for(unsigned y = 0; y < h; y++)
+  for(unsigned x = 0; x < w; x++) {
+    size_t byte_index = (y * w + x) / 2;
+    bool byte_half = (y * w + x) % 2 == 1;
+
+    int color = (int)(4 * ((1 + std::sin(2.0 * 6.28318531 * x / (double)w))
+                         + (1 + std::sin(2.0 * 6.28318531 * y / (double)h))) );
+
+    image[byte_index] |= (unsigned char)(color << (byte_half ? 0 : 4));
+  }
+
+  //encode and save
+  std::vector<unsigned char> buffer;
+  unsigned error = lodepng::encode(buffer, image.empty() ? 0 : &image[0], w, h, state);
+  if(error) {
+    std::cout << "encoder error " << error << ": "<< lodepng_error_text(error) << std::endl;
+    return 0;
+  }
+  lodepng::save_file(buffer, argv[1]);
+}