gistfile1.js

        _showPreview: function(coords) {
            var that = this,
                rateW = that._origWidth / that._previewWidth,
                coefW = 100 / coords.w * rateW,
                rateH = that._origHeight / that._previewHeight,
                coefH = 100 / coords.h * rateH,
                x, y, x2, y2;

            if (!that._preview) return that;
            
            if ((coords.w >= coords.h)) {
                x = Math.round(coefW * coords.x / rateW);
                y = Math.round(coefW * coords.y / rateW);
                x2 = Math.round(coefW * coords.x2 / rateW);
                y2 = Math.round(coefW * coords.y2 / rateW);

                that._preview.elem('thumbimg').css({
                    position: 'absolute',
                    width:  Math.round(that._previewWidth * coefW) + 'px',
                    height: Math.round(that._previewHeight * coefW) + 'px',

                    clip: 'rect(' + y + 'px ' + x2 + 'px ' + y2 + 'px ' + x + 'px)',
                    top: '-' + y + 'px',
                    left: '-' + x + 'px'
                });
            } else {
                x = Math.round(coefH * coords.x / rateH);
                y = Math.round(coefH * coords.y / rateH);
                x2 = Math.round(coefH * coords.x2 / rateH);
                y2 = Math.round(coefH * coords.y2 / rateH);

                that._preview.elem('thumbimg').css({
                    position: 'absolute',
                    width:  Math.round(that._previewWidth * coefH) + 'px',
                    height: Math.round(that._previewHeight * coefH) + 'px',

                    clip: 'rect(' + y + 'px ' + x2 + 'px ' + y2 + 'px ' + x + 'px)',
                    top: '-' + y + 'px',
                    left: '-' + x + 'px'
                });
            }

            return that;
        },