Mr Beam raster scan script for JPG to Gcode conversion

gcodemake.pde

/**
 * Convert a JPG image to gcode for Mr Beam 
 * To use, put the .jpg you want to use in the /data folder of your sketch and adjust the canvas size(x,y) to suit the image,
 * Use the feedrate, laserfloor and lasermax variables to determine how fast and how hard it burns.
 
 This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 */
 
// The next line is needed if running in JavaScript Mode with Processing.js
/* @pjs preload="bender.jpg"; */ 

PImage img;  // Declare variable "a" of type PImage
  float xbed =  435;
  float ybed = 300;
  float feedrate = 800;
  float laserfloor = 90; //highest typical value
  float lasermax = 255; //laser scale factor
  float scale = 20;
  int plotthresh = 30;
  color c;
  int oldgrey = 0;  

PrintWriter output;

void setup() {
  size(299, 616);
  // The image file must be in the data folder of the current sketch 
  // to load successfully
  img = loadImage("input.jpg");  // Load the image into the program  
  noLoop();
  output = createWriter("output.gco"); //this is the name of the output file
  
}

void draw() {
  // Displays the image at its actual size at point (0,0)
  image(img, 0, 0);
 
 
 //set up the output file
 output.println("$H");
 output.println("G92X0Y0Z0");
 output.println("G90");
 output.println("M08");
 output.println("G21");
 output.print("F");
 output.println(feedrate);
 
 
 for (int x = 0; x < width; x = x+2) { //the X axis loop
  for (int y = 0; y < height; y++){ //the forward half of the y axis loop
  
  //y axis forward calculations
  float xpos = x;
  xpos = xpos/scale;
    float ypos = y;
  ypos = ypos/scale;
     color c = get(x,y);
     float red = red(c);
     float green = green(c);
     float blue = blue(c);
     int grey = (int)(red+green+blue)/3;
     color Color =color(grey,grey,grey);
     set(x,y,Color);
     grey = int(laserfloor-((float(grey)/256)*lasermax)); //this is where the laser scaling is done
     //when considering the scale values remember 0 is black on the screen and 255 is white, so we want the reverse.

//if the value is worth plotting, plot it, threshold is set above. Might give odd behaviour at edge cases.
if ((grey != oldgrey)&(grey>plotthresh)) {
  output.print("G1 ");
  output.print('X');
  output.print(nf(xpos,3,4));
  output.print(" ");
  output.print('Y'); 
  output.print(nf(ypos,3,4));
  output.print(" ");
  output.print("M03 S");
  output.println(grey);
}


oldgrey=grey; //pass the last pixel value back, so that the laser just runs on through pixels of the same colour

  }
for (int y = height-1; y > 0; y--){ //loop for negative Y axis, to optimise the raster scan pattern.

//calculations for y axis negative cycle
  float xpos = x+1;
  xpos = xpos/scale;
  float ypos = y;
  ypos = ypos/scale;
  color c = get(x+1,y);
  float red = red(c);
  float green = green(c);
  float blue = blue(c);
  int grey = (int)(red+green+blue)/3;
  color Color =color(grey,grey,grey);
  set(x+1,y,Color);
  grey = int(laserfloor-((float(grey)/256)*lasermax));

  
if ((grey != oldgrey)&(grey>plotthresh)) { //switch to decide if pixel is worth plotting

  output.print("G1 ");
  output.print('X');
  output.print(nf(xpos,3,4));
  output.print(" ");
  output.print('Y');
  output.print(nf(ypos,3,4));
  output.print(" ");
  output.print("M03 S");
  output.println(grey);
}
oldgrey = grey; //pass back the last pixel intensity value
  }
  
}

//close out the .gcode file by turning off the laser and the fan.
output.println("M05");
output.println("M09");
output.flush(); // Writes the remaining data to the file
output.close();
//exit(); 
}