To display a full-sized image of your product like, for example, an uploaded shot 1024 × 768, you must modify the thickbox-modified.js file located under js > jquery.
Replace line 20 :
imgPreloader=new Image();imgPreloader.onload=function(){imgPreloader.onload=null;var pagesize=tb_getPageSize();var x=pagesize[0]-150;var y=pagesize[1]-150;var imageWidth=imgPreloader.width;var imageHeight=imgPreloader.height;if(imageWidth>x){imageHeight=imageHeight*(x/imageWidth);imageWidth=x;if(imageHeight>y){imageWidth=imageWidth*(y/imageHeight);imageHeight=y;}}else if(imageHeight>y){imageWidth=imageWidth*(y/imageHeight);imageHeight=y;if(imageWidth>x){imageHeight=imageHeight*(x/imageWidth);imageWidth=x;}}
with this code:
imgPreloader=new Image();
imgPreloader.onload=function(){
imgPreloader.onload=null;
var imageWidth = imgPreloader.width;var imageHeight = imgPreloader.height;