image_processing/pyramids.cpp
/*******************************************************
* Copyright (c) 2014, ArrayFire
* All rights reserved.
*
* This file is distributed under 3-clause BSD license.
* The complete license agreement can be obtained at:
* https://arrayfire.com/licenses/BSD-3-Clause
********************************************************/
#include <arrayfire.h>
#include <stdio.h>
#include <cstdlib>
using namespace af;
static const float pyramid_kernel[] = {1, 4, 6, 4, 1, 4, 16, 24, 16,
4, 6, 24, 36, 24, 6, 4, 16, 24,
16, 4, 1, 4, 6, 4, 1};
array pyramid(const array& img, const int level, const bool sampling) {
array pyr = img.copy();
array kernel(5, 5, pyramid_kernel);
kernel = kernel / 256.f;
if (sampling) { // Downsample
for (int i = 0; i < level; i++) {
for (int j = 0; j < pyr.dims(2); j++)
pyr(span, span, j) = convolve(pyr(span, span, j), kernel);
pyr = pyr(seq(0, pyr.dims(0) - 1, 2), seq(0, pyr.dims(1) - 1, 2),
span);
}
} else { // Up sample
for (int i = 0; i < level; i++) {
array tmp =
constant(0, pyr.dims(0) * 2, pyr.dims(1) * 2, pyr.dims(2));
tmp(seq(0, 2 * pyr.dims(0) - 1, 2), seq(0, 2 * pyr.dims(1) - 1, 2),
span) = pyr;
for (int j = 0; j < pyr.dims(2); j++)
tmp(span, span, j) = convolve(tmp(span, span, j), kernel * 4.f);
pyr = tmp;
}
}
return pyr;
}
void pyramids_demo() {
af::Window wnd_rgb("Image Pyramids - RGB Images");
af::Window wnd_gray("Image Pyramids - Grayscale Images");
wnd_rgb.setPos(25, 25);
wnd_gray.setPos(150, 150);
array img_rgb =
loadImage(ASSETS_DIR "/examples/images/atlantis.png", true) /
255.f; // 3 channel RGB [0-1]
array img_gray = colorSpace(img_rgb, AF_GRAY, AF_RGB);
array downc1 = pyramid(img_rgb, 1, true);
array downc2 = pyramid(img_rgb, 2, true);
array upc1 = pyramid(img_rgb, 1, false);
array upc2 = pyramid(img_rgb, 2, false);
array downg1 = pyramid(img_gray, 1, true);
array downg2 = pyramid(img_gray, 2, true);
array upg1 = pyramid(img_gray, 1, false);
array upg2 = pyramid(img_gray, 2, false);
while (!wnd_rgb.close() && !wnd_gray.close()) {
wnd_rgb.grid(2, 3);
wnd_rgb(0, 0).image(img_rgb, "color image");
wnd_rgb(1, 0).image(downc1, "downsample 1 level");
wnd_rgb(0, 1).image(downc2, "downsample 2 levels");
wnd_rgb(1, 1).image(upc1, "upsample 1 level");
wnd_rgb(0, 2).image(upc2, "upsample 2 level");
wnd_rgb.show();
wnd_gray.grid(2, 3);
wnd_gray(0, 0).image(img_gray, "grayscale image");
wnd_gray(1, 0).image(downg1, "downsample 1 level");
wnd_gray(0, 1).image(downg2, "downsample 2 levels");
wnd_gray(1, 1).image(upg1, "upsample 1 level");
wnd_gray(0, 2).image(upg2, "upsample 2 level");
wnd_gray.show();
}
}
int main(int argc, char** argv) {
int device = argc > 1 ? atoi(argv[1]) : 0;
try {
af::setDevice(device);
printf("** ArrayFire Image Pyramids Demo **\n\n");
pyramids_demo();
} catch (af::exception& e) {
fprintf(stderr, "%s\n", e.what());
throw;
}
return 0;
}