


Detailed explanation of how JavaScript obtains the true size of an image
网页页面上的图片尺寸似乎都千篇一律。我们最常见到的带有多图的文章页面中,图的大小通常是和页面的宽度一致,这样看起来,页面就是一个直筒形,这样的布局看多了就会觉得很单调。之所以形成这样的局面,我想很大程度上是因为老式浏览器的限制。但随着现代浏览器(火狐/谷歌/IE11)的普及,浏览器对页面设计的限制越来越少,Web程序员的想象能力能够得到极大的发挥。
比如,冷知识:你知道每个视窗都有的 [x] 是怎么来的吗?这篇文章中,很多图片超出了文本宽度的限制,给人一种参差错落的感觉,同时,让大图片以其真实的尺寸展示,给人以更震撼的感觉。
但从技术上,我们可以轻松的用文本的最大宽度限制图片,让它们都保持一个宽度,而不按文本的宽度时,我们就需要每个图片的自己的尺寸。我们可以在服务端编辑时声明图片的原始尺寸。而一种更灵活的方式是通过在页面上放一段js来动态的获取图片的原始大小尺寸,动态改变图片的显示大小。这样即能兼容老的也文本最大宽度的方式,还可以在需要的时候让图片呈现出其原始的大小。
如何用JavaScript在浏览器端获取图片的原始尺寸大小?
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var
img = $(“#img_id”);
// Get my img elem
var
pic_real_width, pic_real_height;
$(“<img/>”)
// Make in memory copy of image to avoid css issues
.attr(“src”, $(img).attr(“src”))
.load(
function
() {
pic_real_width = this.width;
// Note: $(this).width() will not
pic_real_height = this.height;
// work for in memory images.
});
Copy after login
Webkit浏览器(谷歌浏览器等)是在图片的loaded事件之后才能获取高度和宽度值。所以,你不能使用timeout函数延时等待,最好的方法是使用图片的onload事件。
为了避免CSS对图片大小尺寸的影响,上面的代码将图片拷贝到内存中进行计算。
如果你的页面是老式页面,你可以按需把这段代码嵌入页面底部,它不需要你修改原有页面
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