--- /dev/null
+/**
+ * @file interferometer.c
+ * @purpose Implementation of interferometer related functions
+ */
+
+#include "cv.h"
+#include "highgui_c.h"
+#include "interferometer.h"
+#include "analysis.h"
+#include <math.h>
+
+/** Buffer for storing image data. Stored as a single intensity value for the laser light **/
+static CvMat * g_data = NULL;
+
+
+/** Camera capture pointer **/
+static CvCapture * g_capture = NULL;
+
+
+struct timeval start;
+
+#define PI 3.141592
+
+// For testing purposes
+double test_omega = 0.05;
+double test_angle = PI/2;
+double test_noise[] = {0,0,0.02};
+double test_phase = 0;
+double test_intensity = 1.0;
+
+
+static void Interferometer_TestSinusoid()
+{
+ if (g_capture == NULL)
+ {
+ g_capture = cvCreateCameraCapture(0);
+ }
+
+ // Get image from camera
+ IplImage * img = cvQueryFrame(g_capture);
+
+ // Convert to CvMat
+ CvMat stub;
+ CvMat * background = cvGetMat(img, &stub, 0, 0);
+ // ... Honestly, I have no idea what the "stub" is for
+
+ if (g_data == NULL)
+ {
+ g_data = cvCreateMat(background->rows, background->cols, CV_32FC3);
+ }
+
+ //cvShowImage("background", background);
+
+ for (int x = 0; x < g_data->cols-1; ++x)
+ {
+ for (int y = 0; y < g_data->rows-1; ++y)
+ {
+ // Calculate pure sine in test direction
+ double r = x*cos(test_angle) + y*sin(test_angle);
+ double value = 0.5*test_intensity*(1+sin(test_omega*r + test_phase));
+
+ CvScalar s;
+ s.val[0] = 0; s.val[1] = 0; s.val[2] = value;
+ CvScalar b = cvGet2D(background, y, x);
+
+
+ // Add noise & background image
+
+ // Get the order the right way round
+ double t = b.val[0];
+ b.val[0] = b.val[2];
+ b.val[2] = t;
+ for (int i = 0; i < 3; ++i)
+ {
+
+ s.val[i] += (rand() % 1000) * 1e-3 * test_noise[i];
+ s.val[i] += b.val[i] / 255; // Camera image is 0-255
+ }
+
+ //printf("set %d,%d\n", x, y);
+
+
+
+ cvSet2D(g_data,y, x, s);
+ }
+ }
+
+
+}
+
+
+/**
+ * Get an image from the Interferometer
+ */
+static void Interferometer_GetImage()
+{
+
+
+ Interferometer_TestSinusoid();
+ //TODO: Implement camera
+
+}
+
+/**
+ * Initialise the Interferometer
+ */
+void Interferometer_Init()
+{
+
+ // Make an initial reading (will allocate memory the first time only).
+ Interferometer_Read(1);
+}
+
+/**
+ * Cleanup Interferometer stuff
+ */
+void Interferometer_Cleanup()
+{
+ if (g_data != NULL)
+ cvReleaseMat(&g_data);
+
+ if (g_capture != NULL)
+ cvReleaseCapture(&g_capture);
+
+}
+
+/**
+ * Read the interferometer; gets the latest image, processes it, spits out a single number
+ * @param samples - Number of columns to scan (increasing will slow down performance!)
+ * @returns Value proportional to the change in interferometer path length since the last call to this function
+ */
+double Interferometer_Read(int samples)
+{
+
+
+
+
+ // Get the latest image
+ Interferometer_GetImage();
+ // Frequency of the sinusoid
+ static double omega = 0;
+ // Stores locations of nodes
+ static int nodes[MAXNODES];
+ // Current phase
+ static double phase = 0;
+
+ // Phase
+ double cur_phase = 0;
+
+ int xstep = g_data->cols / (samples+1);
+
+ // Used for testing to see where the nodes are identified
+ // (Can't modify g_data)
+ static CvMat * test_overlay = NULL;
+ if (test_overlay == NULL)
+ {
+ // Creates a memory leak; don't do this in the final version!
+ test_overlay = cvCreateMat(g_data->rows, g_data->cols, CV_32FC3);
+ }
+ cvZero(test_overlay);
+ //cvCopy(g_data, test_overlay, NULL);
+
+ // For each column to sample
+ for (int x = xstep; x < g_data->cols; x += xstep)
+ {
+
+ double avg = 0.5; //TODO: Calculate from image
+ double threshold_dif = 0; //TODO: Pick this value
+
+ int num_nodes = 0;
+
+ // Find nodes
+ for (int y = 1; y < g_data->rows-2 && num_nodes < MAXNODES; ++y)
+ {
+ if (num_nodes == 0 || abs(nodes[num_nodes-1] - y) > 1)
+ {
+ // A "node" is defined where the ajacent points are on opposite sides of the avg
+ double ldif = INTENSITY(cvGet2D(g_data, y-1,x)) - avg;
+ double rdif = INTENSITY(cvGet2D(g_data, y+1,x)) - avg;
+
+ // If that is the case, the product of the differences will be negative
+ if (ldif * rdif < -threshold_dif)
+ {
+
+ nodes[num_nodes++] = y;
+
+ // Put a white line on the overlay to indicate the node was found
+ for (int xx = 0; xx < g_data->cols; ++xx)
+ {
+ CvScalar s; // = cvGet2D(g_data, y, xx);
+ s.val[0] = 1; s.val[1] = 1; s.val[2] = 1;
+ cvSet2D(test_overlay, y, xx, s);
+ }
+ }
+ }
+ }
+
+ // Insufficient nodes found to continue
+ if (num_nodes < 2)
+ {
+ --samples;
+ continue;
+ }
+
+ // Estimate angular frequency from two nodes TODO: Average between nodes
+ double slice_omega = (PI*(num_nodes-1)) / (nodes[num_nodes-1] - nodes[0]);
+ //printf("SLICE: %f vs %f\n", slice_omega, test_omega);
+
+ double slice_phase = 0;
+ for (int i = 0; i < num_nodes; ++i)
+ {
+ double this_phase = ((double)(i)*PI - slice_omega * nodes[i]);
+ //printf("Node %d gives phase %f\n", i, this_phase);
+ slice_phase += this_phase;
+ }
+ slice_phase /= num_nodes;
+ cur_phase += slice_phase;
+ }
+
+ // Average over samples
+ if (samples == 0)
+ return 0;
+
+ cur_phase /= samples;
+
+
+
+ // Get phase change since last call, save current phase
+ double result = (cur_phase - phase);
+
+ // HACK
+ if (abs(result) > 0.5*PI)
+ {
+ if (result > 0)
+ result -= PI;
+ else
+ result += PI;
+ }
+ phase = cur_phase;
+
+ // Display the image with lines to indicate results of data processing
+ //cvShowImage("nodes", test_overlay);
+ //cvWaitKey(1);
+ cvAdd(test_overlay, g_data, test_overlay, NULL);
+ cvShowImage("overlay", test_overlay);
+ cvWaitKey(1);
+ return result;
+
+}
+
+/**
+ * For testing purposes
+ */
+int main(int argc, char ** argv)
+{
+ //cvNamedWindow( "display", CV_WINDOW_AUTOSIZE );// Create a window for display.
+ gettimeofday(&start, NULL);
+
+ //Interferometer_Read(1);
+ //exit(EXIT_SUCCESS);
+
+ Interferometer_Init();
+
+ double sum = 0;
+ double last_phase = test_phase;
+
+ struct timeval now;
+ double time = 0;
+
+ while (time < 20)
+ {
+ gettimeofday(&now, NULL);
+ time = TIMEVAL_DIFF(now, start);
+
+ test_phase = 0.5*PI*sin(time);
+
+
+ double delta = Interferometer_Read(1);
+ sum += delta;
+
+ printf("%f\t%f\t%f\t%f\t%f\n", time, test_phase - last_phase, test_phase, delta, sum);
+
+ last_phase = test_phase;
+ //break;
+ }
+
+}
+
+
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