Difference between revisions of "Software"

Revision as of 17:19, 13 February 2013

Image pre-processing

assuming GIMP:

• Push up the contrast
• Image ==> Mode ==> Indexed
• B/W (1 bit palette)
• Dithering: Floyd-Steinberg

Processing code

for the conversion from the image file to the pen tip path

Step by Step:

1. Install Processing
2. Download and Install toxiclib
3. Create a sketch with the code below:

<source lang="javascript"> import toxi.geom.*;

// tsp variables int particleRouteLength; Vec2D[] particles; int[] particleRoute; int maxParticles;

// image variable PImage img;

float millisLastFrame = 0; float frameTime = 0; // scale of the drawing float s = 2.0;

void setup() {

 maxParticles = 15000;
 //img = loadImage("lenna-lg_BW_loRes.png");
 //img = loadImage("test.png");
 img = loadImage("lenna_BW_loRes2.png");
 size(img.width*(int)s, img.height*(int)s);
 //size(400, 600);
 // count black pixels
 int i;
 maxParticles = 0;
 for ( int x = 0; x < img.width; x++ ) {
   for ( int y = 0; y < img.height; y++ ) { 
     i = ( ( y * img.width ) + x ); // getting pixel index
     if ( img.pixels[i] == color( 0, 0, 0 ) ) {
       maxParticles++;
     }
   }
 }

 println("black dots: " + maxParticles);
 // allocate and fill points vector
 particles = new Vec2D[maxParticles];
 i = 0;
 int j = 0;
 for ( int x = 0; x < img.width; x++ ) {
   for ( int y = 0; y < img.height; y++ ) { 
     i = ( ( y * img.width ) + x );
     if ( img.pixels[i] == color( 0, 0, 0 ) ) {
       Vec2D p1 = new Vec2D(x, y);
       particles[j] = p1;
       j++;
     }
   }
 }
 millisLastFrame = millis();
 initPath();    // initialize path (NN heuristic)
 for (int l = 0; l < 5; l++ ) {
   // optimize path with 2-opt heuristic
   for (int k = 0; k < 5000; k++ ) optimizePath();
   // profiling ...
   frameTime = (millis() - millisLastFrame)/1000;
   millisLastFrame = millis();
   println("Frame time: " + millisLastFrame);
 }
 noLoop();

}

void initPath() {

 int temp;
 println("initializing path (NN)");
 Vec2D p1, p2;
 particleRouteLength = maxParticles;
 // array of free ramaining particles to be queried
 boolean freeParticles[] = new boolean[maxParticles]; 
 particleRoute = new int[particleRouteLength]; 
 int closestParticle;
 float distMin;
 p1 = particles[0];
 freeParticles[0] = true;
 particleRoute[0] = 0;
 // Nearest neighbor ("Simple, Greedy") algorithm path optimization:
 int i = 0, j;
 float dx, dy, distance; 
 while (i < particleRouteLength) {
   distMin = Float.MAX_VALUE; // re-initialize mimimun distance value
   closestParticle = 0;      // re-initialize closest particle
   for (j = 0; j < particleRouteLength; j++) {
     if (freeParticles[j] == false) {
       p2 = particles[j];  // get next particle to calculate distance
       dx = p1.x - p2.x;
       dy = p1.y - p2.y;
       distance = (float) (dx*dx+dy*dy);  // Only looking for closest; do not need sqrt factor!
       if (distance < distMin) {
         closestParticle = j;  // update the closest particle index
         distMin = distance;  // update the minimum distance value
       }
     }
   }
   freeParticles[closestParticle] = true; // remove the particle from the ones to be queried
   particleRoute[i] = closestParticle; //set the next particle in the path
   i++; // increment while counter
 }
 // Initial routing is complete
 frameTime = (millis() - millisLastFrame)/1000;
 millisLastFrame = millis();
 println("Frame time: " + millisLastFrame);

}

void optimizePath() {

 // 2-opt heuristic optimization:
 // Identify a pair of edges that would become shorter by reversing part of the tour.
 int temp;
 //println("optimizing path (2-opt) " );
 for (int i = 0; i < 5000; ++i) {   // 1000 tests per frame; you can edit this number.
   int indexA = floor(random(particleRouteLength - 1));
   int indexB = floor(random(particleRouteLength - 1));
   if (Math.abs(indexA  - indexB) < 2)
     continue;
   if (indexB < indexA) {  // swap A, B.
     temp = indexB;
     indexB = indexA;
     indexA = temp;
   }

   Vec2D a0 = particles[particleRoute[indexA]];
   Vec2D a1 = particles[particleRoute[indexA + 1]];
   Vec2D b0 = particles[particleRoute[indexB]];
   Vec2D b1 = particles[particleRoute[indexB + 1]];

   // Original distance:
   float  dx = a0.x - a1.x;
   float  dy = a0.y - a1.y;
   float  distance = (float) (dx*dx+dy*dy);  // only a comparison; do not need sqrt factor! 
   dx = b0.x - b1.x;
   dy = b0.y - b1.y;
   distance += (float) (dx*dx+dy*dy);  //  only a comparison; do not need sqrt factor! 
   // Possible shorter distance?
   dx = a0.x - b0.x;
   dy = a0.y - b0.y;
   float distance2 = (float) (dx*dx+dy*dy);  //  only a comparison; do not need sqrt factor! 
   dx = a1.x - b1.x;
   dy = a1.y - b1.y;
   distance2 += (float) (dx*dx+dy*dy);  // only a comparison; do not need sqrt factor! 

   if (distance2 < distance) { // Reverse tour between a1 and b0.   
     int indexhigh = indexB;
     int indexlow = indexA + 1;
     while (indexhigh > indexlow) {
       temp = particleRoute[indexlow];
       particleRoute[indexlow] = particleRoute[indexhigh];
       particleRoute[indexhigh] = temp;
       indexhigh--;
       indexlow++;
     }
   }
 }

}

void draw() {

 //image(img, 0, 0);
 image(img, width*s, height*s);
 int i = 0;
 stroke(128, 128, 255);    // Stroke color (blue)
 strokeWeight (.5);        // stroke weight
 println("in draw, n.part : " + particleRouteLength);

 // loop the particles drawing a line between successive points
 for ( i = 0; i < (particleRouteLength - 1); ++i) {
   Vec2D p1 = particles[particleRoute[i]];
   Vec2D p2 = particles[particleRoute[i + 1]];
   line(p1.x*s, p1.y*s, p2.x*s, p2.y*s);
 }

} </source>

Python code

for the low level controller

<source lang="python">

def getStringsLen(pos_xy, halfPullDist, scale):

   x2 = (pos_xy[0] * scale)**2
   x2b2 = (halfPullDist - pos_xy[0] * scale)**2
   y2 = (pos_xy[1] * scale)**2
   return [sqrt(x2+y2) , sqrt(x2b2+y2)]

from time import sleep, clock

1. import RPi.GPIO as GPIO

from numpy import loadtxt, pi, sqrt, subtract

1. load path file

path = loadtxt("path.txt")

1. print path

1. systems parameters

r_p = 18.0 #............... pulley radius [mm] d_p = 1500.0 #............. pulley distance [mm] d_p05 = d_p * 0.5 #........ half pulley distance [mm] s_a = 3.5 * (2*pi/360) #... step angle [rad]

1. drawing parameters

s = 2.0 #.................. drawing scale [-]

1. initialize drawing

pos_init = [240, 240] #........................... set initial position vector (x,y) len_curr = getStringsLen(pos_init, d_p05, s) # ..... get initial string

for i in path:

   pos_next = i #................................. allocate next position vector
   len_next = getStringsLen(pos_next, d_p05, s) #. get next strings lengths
   dl = subtract(len_next, len_curr) #............ get string lengths difference 
   ds = dl/s_a #.................................. compute motor step (same step angles for both motors)
   print ds

</source>