我正在创建一个jQuery插件。
我如何得到真实的图像宽度和高度与Javascript在Safari?
Firefox 3、IE7和Opera 9的操作如下:
var pic = $("img")
// need to remove these in of case img-element has set width and height
pic.removeAttr("width");
pic.removeAttr("height");
var pic_real_width = pic.width();
var pic_real_height = pic.height();
但在Safari和谷歌等Webkit浏览器中，Chrome的值为0。
当前回答
使用HTML5中的naturalHeight和naturalWidth属性。
例如:
var h = document.querySelector('img').naturalHeight;
工作在IE9+， Chrome, Firefox, Safari和Opera(统计)。
其他回答
这适用于我(safari 3.2)，从窗口内发射。onload事件:
$(window).load(function() {
var pic = $('img');
pic.removeAttr("width");
pic.removeAttr("height");
alert( pic.width() );
alert( pic.height() );
});
我们如何在不眨眼的情况下获得正确的真实尺寸:
(function( $ ){
$.fn.getDimensions=function(){
alert("First example:This works only for HTML code without CSS width/height definition.");
w=$(this, 'img')[0].width;
h=$(this, 'img')[0].height;
alert("This is a width/height on your monitor: " + $(this, 'img')[0].width+"/"+$(this, 'img')[0].height);
//This is bad practice - it shows on your monitor
$(this, 'img')[0].removeAttribute( "width" );
$(this, 'img')[0].removeAttribute( "height" );
alert("This is a bad effect of view after attributes removing, but we get right dimensions: "+ $(this, 'img')[0].width+"/"+$(this, 'img')[0].height);
//I'am going to repare it
$(this, 'img')[0].width=w;
$(this, 'img')[0].height=h;
//This is a good practice - it doesn't show on your monitor
ku=$(this, 'img').clone(); //We will work with a clone
ku.attr( "id","mnbv1lk87jhy0utrd" );//Markup clone for a final removing
ku[0].removeAttribute( "width" );
ku[0].removeAttribute( "height" );
//Now we still get 0
alert("There are still 0 before a clone appending to document: "+ $(ku)[0].width+"/"+$(ku)[0].height);
//Hide a clone
ku.css({"visibility" : "hidden",'position':'absolute','left':'-9999px'});
//A clone appending
$(document.body).append (ku[0]);
alert("We get right dimensions: "+ $(ku)[0].width+"/"+$(ku)[0].height);
//Remove a clone
$("#mnbv1lk87jhy0utrd").remove();
//But a next resolution is the best of all. It works in case of CSS definition of dimensions as well.
alert("But if you want to read real dimensions for image with CSS class definition outside of img element, you can't do it with a clone of image. Clone method is working with CSS dimensions, a clone has dimensions as well as in CSS class. That's why you have to work with a new img element.");
imgcopy=$('<img src="'+ $(this, 'img').attr('src') +'" />');//new object
imgcopy.attr( "id","mnbv1lk87jhy0aaa" );//Markup for a final removing
imgcopy.css({"visibility" : "hidden",'position':'absolute','left':'-9999px'});//hide copy
$(document.body).append (imgcopy);//append to document
alert("We get right dimensions: "+ imgcopy.width()+"/"+imgcopy.height());
$("#mnbv1lk87jhy0aaa").remove();
}
})( jQuery );
$(document).ready(function(){
$("img.toreaddimensions").click(function(){$(this).getDimensions();});
});
<img class="toreaddimensions"…
这对缓存的和动态加载的图像都有效。
function LoadImage(imgSrc, callback){
var image = new Image();
image.src = imgSrc;
if (image.complete) {
callback(image);
image.onload=function(){};
} else {
image.onload = function() {
callback(image);
// clear onLoad, IE behaves erratically with animated gifs otherwise
image.onload=function(){};
}
image.onerror = function() {
alert("Could not load image.");
}
}
}
使用此脚本:
function AlertImageSize(image) {
alert("Image size: " + image.width + "x" + image.height);
}
LoadImage("http://example.org/image.png", AlertImageSize);
演示:http://jsfiddle.net/9543z/2/
根本问题是WebKit浏览器(Safari和Chrome)并行加载JavaScript和CSS信息。因此，JavaScript可能在计算CSS的样式效果之前执行，返回错误的答案。在jQuery中，我发现解决方案是等到文档。readyState == 'complete'，例如，
jQuery(document).ready(function(){
if (jQuery.browser.safari && document.readyState != "complete"){
//console.info('ready...');
setTimeout( arguments.callee, 100 );
return;
}
... (rest of function)
至于宽度和高度……根据你正在做的事情，你可能需要offsetWidth和offsetHeight，其中包括边界和填充。
我使用不同的方法，简单地使Ajax调用服务器，以获得图像对象在使用时的图像大小。
//make json call to server to get image size
$.getJSON("http://server/getimagesize.php",
{"src":url},
SetImageWidth
);
//callback function
function SetImageWidth(data) {
var wrap = $("div#image_gallery #image_wrap");
//remove height
wrap.find("img").removeAttr('height');
//remove height
wrap.find("img").removeAttr('width');
//set image width
if (data.width > 635) {
wrap.find("img").width(635);
}
else {
wrap.find("img").width(data.width);
}
}
当然还有服务器端代码:
<?php
$image_width = 0;
$image_height = 0;
if (isset ($_REQUEST['src']) && is_file($_SERVER['DOCUMENT_ROOT'] . $_REQUEST['src'])) {
$imageinfo = getimagesize($_SERVER['DOCUMENT_ROOT'].$_REQUEST['src']);
if ($imageinfo) {
$image_width= $imageinfo[0];
$image_height= $imageinfo[1];
}
}
$arr = array ('width'=>$image_width,'height'=>$image_height);
echo json_encode($arr);
?>
