Spinner Synth Prototype

//
// SpinnerSynth
//
// Really simple rotary synth controller using OpenCV.  It's probably not the
// most elegant way to go about things, and all the important values are more
// or less hardcoded into it, so good luck :-D.
//
// By Matt Mets, June 2009.
//
// Based on the example from http://opencv.willowgarage.com/wiki/CameraCapture
//
// This code is released as public domain.
 
#include <stdio.h>
#include <fcntl.h>
 
#include "cv.h"
#include "highgui.h"
 
 
// Center of the sensing region
#define centerX 320
#define centerY 240
 
// Size of the sensing areas
#define rectWidthX  3
#define rectWidthY  3
 
// Number of sensing regions
#define numSensors 4
 
#define midiPort "/dev/midi"
 
unsigned char channelBlue[numSensors] = {1, 2, 2, 3};   // MIDI channels
unsigned char noteBlue[numSensors] = {48, 52, 57, 60};  // MIDI notes
 
unsigned char noteOn[numSensors] = {0, 0, 0, 0};    // State trackers
unsigned char noteBlueOnVal[numSensors];
 
int main()
{
 
    // open the midi device
    char* device =  midiPort;
 
    // step 1: open the OSS device for writing
    int midi = open(device, O_WRONLY, 0);
    if (midi < 0) {
        printf("Error: cannot open %s\n", device);
        exit(1);
    }
 
    CvCapture* capture = cvCaptureFromCAM( CV_CAP_ANY );
    if( !capture ) {
        fprintf( stderr, "ERROR: capture is NULL \n" );
        getchar();
        return -1;
    }
 
    // See if we can bump up the frame rate (no effect)
//    cvSetCaptureProperty(capture, CV_CAP_PROP_FPS, 30);
//    cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH, 320); 
//    cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT, 240); 
 
    // Create a window in which the captured images will be presented
    cvNamedWindow( "SpinnerSynth", CV_WINDOW_AUTOSIZE );
 
    // Show the image captured from the camera in the window and repeat
    while( 1 )
    {
        // Grab an image frame
        IplImage* frame = cvQueryFrame( capture );
        if( !frame ) {
            fprintf( stderr, "ERROR: frame is null...\n" );
            getchar();
            break;
        }
 
        // Draw a line to represent the scanner location
        cvLine( frame,
                cvPoint(centerX+15,centerY),
                cvPoint(centerX+215,centerY-105),
                CV_RGB(0,0,128),
                2, 8, 0);
 
        // Read in each rectangle's data
        unsigned int i;
        for ( i = 0; i < numSensors; i++) {
 
            // Determine the rectangle boundaries
            unsigned int rectX = centerX - 20 + (i+1)*44 + 8*i;
            unsigned int rectY = centerY + 10 - (i+1)*22 - 6*i;
 
            // Construct objects to hold the cut out piece of image data that
            // is to be sensed
            CvRect rect = cvRect(rectX, rectY, rectWidthX, rectWidthY);
            CvMat* mat = cvCreateMat(rectWidthX, rectWidthY, CV_8UC1);
            CvScalar value;
 
 
            // Draw a box to outline the sampling region
            cvRectangle( frame,
                         cvPoint(rectX - 1, rectY - 1),
                         cvPoint(rectX + rectWidthX, rectY + rectWidthY),
                         CV_RGB(0,0,128),
                         1, 8, 0);
 
            // Now figure out what the average of these point's values are
            cvGetSubRect( frame, mat, rect );
            value = cvAvg(mat, NULL);
 
            // Determine if a new note has started or the last note has ended.
            if ( (value.val[0] > 120) && (noteOn[i] == 0) )
            {
                // Do some sort of transformation to make the note interesting,
                // this part is improvised.
                unsigned char velocity = 60 + ((int)value.val[0] - 120);
                unsigned char pitch = noteBlue[i] + velocity/30;
 
                // Construct the MIDI on message and Write to the midi device
                unsigned char data[3] = {0x90 + channelBlue[i], pitch, 90};
                write(midi, data, sizeof(data));
 
                // Record that the note was turned on, and at what pitch.
                noteOn[i] = 1;
                noteBlueOnVal[i] = pitch;
            }
            else if ( (value.val[0] <= 120) && (noteOn[i] == 1) )
            {
                // Construct the MIDI off message and Write to the midi device
                unsigned char data[3] = {0x80 + channelBlue[i],
                                         noteBlueOnVal[i],
                                         0};
                write(midi, data, sizeof(data));
 
                // Record that the note was turned off
                noteOn[i] = 0;
            }
        }
 
        // Show the image
        cvShowImage( "SpinnerSynth", frame );
 
        //If ESC key pressed, Key=0x10001B under OpenCV 0.9.7(linux version),
        //remove higher bits using AND operator
        if( (cvWaitKey(10) & 255) == 27 ) break;
  }
 
  // Release the capture device housekeeping
  cvReleaseCapture( &capture );
  cvDestroyWindow( "SpinnerSynth" );
 
  // Close the MIDI device
  close(midi);
 
  return 0;
}