I do not have a solution that I am sure of will prevent the vertical lines from appearing.
I do however have a couple of tips to improve your code so performance increases and you might have a chance that the lines disappear.
Cache the image element outside of your move function:
var image = $("#img_id")[0];
In your code, there is no reason to query the image ID against the DOM every 3 milliseconds. jQuery's selector engine, Sizzle has to a lot of work¹.
Don't use the jQuery CSS function:
image.style.left = pos_new;
Setting a property object is faster than a function call. In the case of the jQuery css function, there are at least two function calls (one to css and one inside css).
Use interval instead of timeout:
setInterval(move, refresh);
I would consider an interval for one-off animations I wanted to be as
smooth as possible
setTimeout or setInterval?
One other option for smoother animation is to use CSS transitions or animations. A great introduction and comparison can be found in CSS Animations and JavaScript by John Resig
Browser support table: http://caniuse.com/#search=transition
A JavaScript library that I find makes CSS animation via JavaScript very easy is morpheus.
¹ Under the hood, this is the code it goes through every 3 milliseconds to find your image:
In a browser that supports querySelectorAll:
Sizzle = function( query, context, extra, seed ) {
context = context || document;
// Only use querySelectorAll on non-XML documents
// (ID selectors don't work in non-HTML documents)
if ( !seed && !Sizzle.isXML(context) ) {
// See if we find a selector to speed up
var match = /^(\w+$)|^\.([\w\-]+$)|^#([\w\-]+$)/.exec( query );
if ( match && (context.nodeType === 1 || context.nodeType === 9) ) {
// Speed-up: Sizzle("TAG")
if ( match[1] ) {
return makeArray( context.getElementsByTagName( query ), extra );
// Speed-up: Sizzle(".CLASS")
} else if ( match[2] && Expr.find.CLASS && context.getElementsByClassName ) {
return makeArray( context.getElementsByClassName( match[2] ), extra );
}
}
if ( context.nodeType === 9 ) {
// Speed-up: Sizzle("body")
// The body element only exists once, optimize finding it
if ( query === "body" && context.body ) {
return makeArray( [ context.body ], extra );
// Speed-up: Sizzle("#ID")
} else if ( match && match[3] ) {
var elem = context.getElementById( match[3] );
// Check parentNode to catch when Blackberry 4.6 returns
// nodes that are no longer in the document #6963
if ( elem && elem.parentNode ) {
// Handle the case where IE and Opera return items
// by name instead of ID
if ( elem.id === match[3] ) {
return makeArray( [ elem ], extra );
}
} else {
return makeArray( [], extra );
}
}
try {
return makeArray( context.querySelectorAll(query), extra );
} catch(qsaError) {}
// qSA works strangely on Element-rooted queries
// We can work around this by specifying an extra ID on the root
// and working up from there (Thanks to Andrew Dupont for the technique)
// IE 8 doesn't work on object elements
} else if ( context.nodeType === 1 && context.nodeName.toLowerCase() !== "object" ) {
var oldContext = context,
old = context.getAttribute( "id" ),
nid = old || id,
hasParent = context.parentNode,
relativeHierarchySelector = /^\s*[+~]/.test( query );
if ( !old ) {
context.setAttribute( "id", nid );
} else {
nid = nid.replace( /'/g, "\\$&" );
}
if ( relativeHierarchySelector && hasParent ) {
context = context.parentNode;
}
try {
if ( !relativeHierarchySelector || hasParent ) {
return makeArray( context.querySelectorAll( "[id='" + nid + "'] " + query ), extra );
}
} catch(pseudoError) {
} finally {
if ( !old ) {
oldContext.removeAttribute( "id" );
}
}
}
}
return oldSizzle(query, context, extra, seed);
};
And a browser that doesn't:
var Sizzle = function( selector, context, results, seed ) {
results = results || [];
context = context || document;
var origContext = context;
if ( context.nodeType !== 1 && context.nodeType !== 9 ) {
return [];
}
if ( !selector || typeof selector !== "string" ) {
return results;
}
var m, set, checkSet, extra, ret, cur, pop, i,
prune = true,
contextXML = Sizzle.isXML( context ),
parts = [],
soFar = selector;
// Reset the position of the chunker regexp (start from head)
do {
chunker.exec( "" );
m = chunker.exec( soFar );
if ( m ) {
soFar = m[3];
parts.push( m[1] );
if ( m[2] ) {
extra = m[3];
break;
}
}
} while ( m );
if ( parts.length > 1 && origPOS.exec( selector ) ) {
if ( parts.length === 2 && Expr.relative[ parts[0] ] ) {
set = posProcess( parts[0] + parts[1], context, seed );
} else {
set = Expr.relative[ parts[0] ] ?
[ context ] :
Sizzle( parts.shift(), context );
while ( parts.length ) {
selector = parts.shift();
if ( Expr.relative[ selector ] ) {
selector += parts.shift();
}
set = posProcess( selector, set, seed );
}
}
} else {
// Take a shortcut and set the context if the root selector is an ID
// (but not if it'll be faster if the inner selector is an ID)
if ( !seed && parts.length > 1 && context.nodeType === 9 && !contextXML &&
Expr.match.ID.test(parts[0]) && !Expr.match.ID.test(parts[parts.length - 1]) ) {
ret = Sizzle.find( parts.shift(), context, contextXML );
context = ret.expr ?
Sizzle.filter( ret.expr, ret.set )[0] :
ret.set[0];
}
if ( context ) {
ret = seed ?
{ expr: parts.pop(), set: makeArray(seed) } :
Sizzle.find( parts.pop(), parts.length === 1 && (parts[0] === "~" || parts[0] === "+") && context.parentNode ? context.parentNode : context, contextXML );
set = ret.expr ?
Sizzle.filter( ret.expr, ret.set ) :
ret.set;
if ( parts.length > 0 ) {
checkSet = makeArray( set );
} else {
prune = false;
}
while ( parts.length ) {
cur = parts.pop();
pop = cur;
if ( !Expr.relative[ cur ] ) {
cur = "";
} else {
pop = parts.pop();
}
if ( pop == null ) {
pop = context;
}
Expr.relative[ cur ]( checkSet, pop, contextXML );
}
} else {
checkSet = parts = [];
}
}
if ( !checkSet ) {
checkSet = set;
}
if ( !checkSet ) {
Sizzle.error( cur || selector );
}
if ( toString.call(checkSet) === "[object Array]" ) {
if ( !prune ) {
results.push.apply( results, checkSet );
} else if ( context && context.nodeType === 1 ) {
for ( i = 0; checkSet[i] != null; i++ ) {
if ( checkSet[i] && (checkSet[i] === true || checkSet[i].nodeType === 1 && Sizzle.contains(context, checkSet[i])) ) {
results.push( set[i] );
}
}
} else {
for ( i = 0; checkSet[i] != null; i++ ) {
if ( checkSet[i] && checkSet[i].nodeType === 1 ) {
results.push( set[i] );
}
}
}
} else {
makeArray( checkSet, results );
}
if ( extra ) {
Sizzle( extra, origContext, results, seed );
Sizzle.uniqueSort( results );
}
return results;
};
