A high-performance general-purpose compute library
* Copyright (c) 2015, ArrayFire
* All rights reserved.
* This file is distributed under 3-clause BSD license.
* The complete license agreement can be obtained at:
* http://arrayfire.com/licenses/BSD-3-Clause
#include <arrayfire.h>
#include <cstdio>
#include <cstdlib>
using namespace af;
static void fast_demo(bool console) {
// Load image
array img_color;
if (console)
img_color = loadImage(ASSETS_DIR "/examples/images/square.png", true);
img_color = loadImage(ASSETS_DIR "/examples/images/man.jpg", true);
// Convert the image from RGB to gray-scale
array img = colorSpace(img_color, AF_GRAY, AF_RGB);
// For visualization in ArrayFire, color images must be in the [0.0f-1.0f]
// interval
img_color /= 255.f;
features feat = fast(img, 20.0f, 9, true, 0.05);
float* h_x = feat.getX().host<float>();
float* h_y = feat.getY().host<float>();
// Draw draw_len x draw_len crosshairs where the corners are
const int draw_len = 3;
for (size_t f = 0; f < feat.getNumFeatures(); f++) {
int x = h_x[f];
int y = h_y[f];
img_color(y, seq(x - draw_len, x + draw_len), 0) = 0.f;
img_color(y, seq(x - draw_len, x + draw_len), 1) = 1.f;
img_color(y, seq(x - draw_len, x + draw_len), 2) = 0.f;
// Draw vertical line of (draw_len * 2 + 1) pixels centered on the
// corner Set only the first channel to 1 (green lines)
img_color(seq(y - draw_len, y + draw_len), x, 0) = 0.f;
img_color(seq(y - draw_len, y + draw_len), x, 1) = 1.f;
img_color(seq(y - draw_len, y + draw_len), x, 2) = 0.f;
printf("Features found: %zu\n", feat.getNumFeatures());
if (!console) {
af::Window wnd("FAST Feature Detector");
// Previews color image with green crosshairs
while (!wnd.close()) wnd.image(img_color);
} else {
int main(int argc, char** argv) {
int device = argc > 1 ? atoi(argv[1]) : 0;
bool console = argc > 2 ? argv[2][0] == '-' : false;
try {
printf("** ArrayFire FAST Feature Detector Demo **\n\n");
} catch (af::exception& ae) {
fprintf(stderr, "%s\n", ae.what());
return 0;
Window object to render af::arrays.
Definition: graphics.h:37
A multi dimensional data container.
Definition: array.h:37
T * host() const
Copy array data to host and return host pointer.
An ArrayFire exception class.
Definition: exception.h:22
virtual const char * what() const
Returns an error message for the exception in a string format.
Definition: exception.h:46
Represents a feature returned by a feature detector.
Definition: features.h:24
array getY() const
Returns an af::array which represents the y locations of a feature.
size_t getNumFeatures() const
Returns the number of features represented by this object.
array getX() const
Returns an af::array which represents the x locations of a feature.
seq is used to create sequences for indexing af::array
Definition: seq.h:46
Definition: defines.h:340
3-channel RGB
Definition: defines.h:341
AFAPI void info()
AFAPI void setDevice(const int device)
Sets the current device.
void image(const array &in, const char *title=NULL)
Renders the input array as an image to the window.
bool close()
Check if window is marked for close.
Definition: algorithm.h:15
#define af_print(...)
Definition: util.h:148