Click part of the image to store a number in a 2d array representing the rectangles of the image.

Click a rectangle multiple times and it will toggle between 1 and 2.

A colour-coded rectangle appears on the image to show what value was in the array before it was updated.

This is intended as a demo of one way to treat an image as a grid.

imageArray.js

var cellData=[];
//Called when application is started.
function OnStart()
{
    //Create a layout with objects vertically centered.
    var lay = app.CreateLayout( "linear", "VCenter,FillXY" );    
 
    //Create a text label and add it to layout.
    var img = app.CreateImage( null, 0.9, 0.5 );
    img.SetColor("#ff999999")
    img.SetOnTouch(imgOnTouch);
    
    lay.AddChild( img );
    var btnSave=app.CreateButton("Save");
    btnSave.SetOnTouch(btnSaveOnTouch);
    lay.AddChild(btnSave);
    //Add layout to app.    
    app.AddLayout( lay );
}
 
function imgOnTouch(ev)
{
     var row,col,val,x1,y1,x2,y2
     var cellWidth=0.1,cellHeight=0.1;
     if(ev.action==="Down")
     {
         row = Math.floor(ev.Y/cellHeight);
         col = Math.floor(ev.X/cellWidth);
         x1 = col*cellWidth;
         y1 = row*cellHeight;
         x2 = x1 + cellWidth;
         y2 = y1 + cellHeight;
         val = getData(row,col);
         this.SetLineWidth(1);
         this.SetPaintStyle("Fill")
         setData(row,col,(val+1)%2);
         if(val < 0)
         {
            this.SetPaintColor("#ffff0000");
            this.SetPaintStyle("Line")
            this.DrawRectangle(x1,y1,x2,y2);
         }
         else if(val === 0)
         {
            this.SetPaintColor("#ff00ff00");
            this.DrawRectangle(x1,y1,x2,y2);
         }
         else if(val === 1)
         {
            this.SetPaintColor("#ff0000ff");
            this.DrawRectangle(x1,y1,x2,y2);
         }
         app.ShowPopup(val);
     }
}
 
function getData(row,col)
{
   var ret;
   if (cellData.length < row +1)
      return -1;  // represents unset
   ret = cellData[row][col];
   if(ret===undefined)
      return -1;
   return ret;
}
function setData(row,col,value)
{
   while (cellData.length < row +1)
   {
       cellData.push([]);
   }
   cellData[row][col]=value;
}
 
function btnSaveOnTouch()
{
     
    var data = JSON.stringify(cellData);
    app.WriteFile("/sdcard/picData",data)     
}