/* toggle() checks to see if the images has already been faded or not and sends the appropriate variables to opacity(); */ function toggle(el,milli) { // Get the opacity style parameter from the image var currOpacity = document.getElementById(el).style.opacity; if(currOpacity != 0) { // if not faded fade(el, milli, 100, 0); } else { // else the images is already faded fade(el, milli, 0, 100); } } /* changeOpacity() uses three different opacity settings to achieve a cross-browser opacity changing function. This function can also be used to directly change the opacity of an element. */ function changeOpacity(el,opacity) { var image = document.getElementById(el); // For Mozilla image.style.MozOpacity = (opacity / 100); // For IE image.style.filter = "alpha(opacity=" + opacity + ")"; // For others image.style.opacity = (opacity / 100); } /* fade() will fade the image in or out based on the starting and ending opacity settings. The speed of the fade is determined by the variable milli (total time of the fade in milliseconds)*/ function fade(el,milli,start,end) { var fadeTime = Math.round(milli/100); var i = 0; // Fade Timer // Fade in if(start < end) { for(j = start; j <= end; j++) { // define the expression to be called in setTimeout() var expr = "changeOpacity('" + el + "'," + j + ")"; var timeout = i * fadeTime; // setTimeout will call 'expr' after 'timeout' milliseconds setTimeout(expr,timeout); i++; } } // Fade out else if(start > end) { for(j = start; j >= end; j--) { var expr = "changeOpacity('" + el + "'," + j + ")"; var timeout = i * fadeTime; setTimeout(expr,timeout); i++; } } }