// Image Flipping script // Author: June 13, 1997 - Casey Barton (casey@e-commerce.com) // Modified: Aug 22, 1997 - Velimir Otovic (votovic@e-commerce.com) // Oct 15, 1997 - Mike Hesler (mchesler@uwaterloo.ca) // Copyright e-Commerce Inc, 1997 // Based loosely on Jamie Zawinski (jwz@netscape.com)'s home page script. // // Usage: // - Include both blocks into the // block of your page. // // - Insert the attribute // onLoad="do_preload()" // into the tag // // - Each relevant block should resemble // // // // // where 'next1.gif' is the name of the default (unhighlighted) image to be replaced, // 'next2.gif' is the name of an image that is also replaced // // - The highlighted image is then assumed to be named 'nextXa.gif' // (the image name with an appended 'a'), to be found in the // same directory as the default image. // - An image named 'nextXb.gif' will be used to replace the other image // (the image name with an appended 'b'), to be found in the // same directory as the default image. var prefetched = new Array; var imgSrcArray = new Array; var donePreload = false; // Figure out the src attribute of the // highlighted counterpart of an image function highlight_src(imgSrc) { if ( imgSrc != null && imgSrc != 'undefined') { // Just add an 'a' to the image name return imgSrc.substring(0, imgSrc.length - 4) + 'a' + imgSrc.substring(imgSrc.length - 4); } else return null; } // Figure out the src attribute of the // reference counterpart of an image function reference_src(imgSrc) { if ( imgSrc != null && imgSrc != 'undefined') { // Just add an 'b' to the image name return imgSrc.substring(0, imgSrc.length - 4) + 'b' + imgSrc.substring(imgSrc.length - 4); } else return null; } // Get an image into memory function preload_image(imgSrc, width, height) { if ( imgSrc != null && imgSrc != 'undefined') { var i = prefetched.length; var name = highlight_src(imgSrc); prefetched[i] = new Image(width, height); prefetched[i].src = name; i = i + 1; name = reference_src(imgSrc); prefetched[i] = new Image(width, height); prefetched[i].src = name; } } // Find and preload all necessary highlighted images function do_preload() { for (var i in document.images) { if (i != 'length' && isNaN(parseInt('' + i))) { var imgStr = document.images[i].src; imgSrcArray[i] = document.images[i].src; preload_image(imgSrcArray[i], document.images[i].width, document.images[i].height); } } donePreload = true; } // Flip to the highlighted image function turn_on(srcReplace) { if (donePreload && (document.images[srcReplace] != null) && imgSrcArray[srcReplace] != null) { document.images[srcReplace].src = highlight_src(imgSrcArray[srcReplace]); } } // Flip to the highlighted image function turn_ref(srcReplace, refReplace) { if (donePreload && (document.images[srcReplace] != null) && (document.images[refReplace] != null) && (imgSrcArray[srcReplace] != null) ) { document.images[refReplace].src = reference_src(imgSrcArray[srcReplace]); } } // Flip (back) to the regular image function turn_off(imgName) { if (donePreload && (document.images[imgName] != null) && (imgSrcArray[imgName] != null) ) { var imgStr = imgSrcArray[imgName]; if (imgStr != null) document.images[imgName].src = imgStr ; } }