file encode as image pixels

DataView.prototype.getString=function(bi,L){
 var s="";
 while(bi!=L){
  s+=String.fromCharCode(this.getUint8(bi));
  bi++;
 }
 return s;
};

DataView.prototype.setString=function(bi,s){
 var L=s.length,i=0;
 while(i!=L){
  this.setUint8(bi+i,s.charCodeAt(i));
  i++;
 }
};


/*

self.i2=document.createElement("img");
document.body.appendChild(i2);
self.v2=document.createElement("video");v2.controls=!0; document.body.appendChild(v2);


finp=document.querySelector("input[type=file]");
fi=finp.files[0];
fi.arrayBuffer().then(function(a){ self.file_dv1=new DataView(a); });



file_as_png(file_dv1,{"type":fi.type,"name":fi.name},function(r){ self.ri2=r; });

URL.revokeObjectURL(i2.src);
i2.src=URL.createObjectURL(ri2);


self.rez7=open_png_filed(i2);
URL.revokeObjectURL(v2.src);

self.b2=new Blob([rez7[0]],{"type":rez7[1].type||"video/mp4"});
v2.src=URL.createObjectURL(b2);


*/


self.file_as_png=function(file_dv,meta,cb){
var cnvs=document.createElement("canvas"),
bL=file_dv.byteLength,ch=Math.ceil(bL/(2400)),df=(ch*2400)-bL,
ee=new ImageData(800,ch);
cnvs.width=800;
cnvs.height=ch+1; //extra line at the end for metadata
contxt=cnvs.getContext("2d");

//to image
var i=0,i2=2, eda=new DataView(ee.data.buffer);

eda.setUint16(0,df);

while(i<bL){
 if((i2&3)==3){ eda.setUint8(i2,255); i2++; }
 eda.setUint8(i2,file_dv.getUint8(i));
 i++; i2++;
}

//meta
if(meta){
var mds=JSON.stringify(meta /*{"type":"video/mp4","name":"a_file.mp4"}*/)+";\n",mdL=mds.length;
if((i2&3)==3){ eda.setUint8(i2,255); i2++; }
eda.setUint16(i2,mdL); i2+=2;
 //metadata size limit 2390 bytes
 i=0;
while(i<=mdL){
 if((i2&3)==3){ eda.setUint8(i2,255); i2++; }
 eda.setUint8(i2,mds.charCodeAt(i)||255);
 i++; i2++;
}
}

if((i2&3)==3){ eda.setUint8(i2,255); i2++; }


contxt.putImageData(ee,0,0);

cnvs.toBlob(function(a){ self.blb1=a; if(typeof cb=="function")cb(a); });
};





//from image

self.open_png_filed=function(i1){ //input image element
var cnvs=document.createElement("canvas");
cnvs.height=i1.naturalHeight;
cnvs.width=i1.naturalWidth;


ctx=cnvs.getContext("2d");
ctx.drawImage(i1,0,0);
var dat=ctx.getImageData(0,0,cnvs.width,cnvs.height);

var eda=new DataView(dat.data.buffer), df=eda.getUint16(0),bL=(cnvs.width*3*(cnvs.height-1))-df;

var file_dv=new DataView(new ArrayBuffer(bL));




var i=0, i2=2;

while(i<bL){
 if((i2&3)==3) i2++;
 file_dv.setUint8(i,eda.getUint8(i2));
 i++; i2++;
}

//meta
var mda={};
if((i2&3)==3) i2++;
var mdL=eda.getUint16(i2); i2+=2;
//console.log(i); self.eda1=eda; //debuging line
var mds="";

if(mdL<2390){
 i=mdL;
while(i--){
 if((i2&3)==3) i2++;
 mds+=String.fromCharCode(eda.getUint8(i2));
 i2++;
}
 console.log(mds);
 try{ mda=JSON.parse(mds.substr(0,mds.lastIndexOf("}")+1)); }catch(e){}
} //metadata size limit 2390 bytes

return [file_dv,mda];

};