Added FAST feature detector example

Peter Andreas Entschev · Peter Andreas Entschev · commit d41b683607a7 · 2015-05-28T17:41:27.000-04:00
diff --git a/examples/computer_vision/fast.cpp b/examples/computer_vision/fast.cpp
@@ -0,0 +1,81 @@
+/*******************************************************
+ * 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 <cstdio>
+#include <arrayfire.h>
+#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);
+    else
+        img_color = loadImage(ASSETS_DIR "/examples/images/lena.ppm", 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: %lu\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 {
+        af_print(feat.getX());
+        af_print(feat.getY());
+    }
+}
+
+int main(int argc, char** argv)
+{
+    int device = argc > 1 ? atoi(argv[1]) : 0;
+    bool console = argc > 2 ? argv[2][0] == '-' : false;
+
+    try {
+        af::setDevice(device);
+        af::info();
+        std::cout << "** ArrayFire FAST Feature Detector Demo **" << std::endl << std::endl;
+        fast_demo(console);
+
+    } catch (af::exception& ae) {
+        std::cout << ae.what() << std::endl;
+        throw;
+    }
+
+    return 0;
+}
