var MAX_WIDTH   = 100;   
var MAX_HEIGHT  = 75;   
function resizeImage( source_image , max_width , max_height){   
    var image = new Image();   
    image.src = source_image.src;   
    if (!max_width || parseInt(max_width) <= 0){   
        max_width = MAX_WIDTH;   
    }   
    if (!max_height || parseInt(max_height) <= 0){   
        max_height = MAX_HEIGHT;   
    }   
    //¿ªÊ¼¼ì²éͼƬ   
    if(image.width > 0 && image.height > 0 ){   
        var image_rate = 1;   
        if( (max_width / image.width) < (max_height / image.height)){   
            image_rate = max_width / image.width ;   
        }else{   
            image_rate = max_height / image.height ;   
        }   
        if ( image_rate <= 1){   
            source_image.width  = image.width * image_rate;   
            source_image.height = image.height * image_rate;   
        }   
    }   
       
}