js 控制图片大小核心讲解

时间：2021-05-26

缩放图片脚本分享
复制代码 代码如下:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title> New Document </title>
<meta name="Generator" content="EditPlus">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">

<script>

function AutoResizeImage(maxWidth,maxHeight){
var objImg = document.getElementById("operImg");
var img = new Image();
img.src = objImg.src;
var hRatio;
var wRatio;
var Ratio = 1;
var w = img.width;
var h = img.height;
wRatio = maxWidth / w;
hRatio = maxHeight / h;
if (maxWidth ==0 && maxHeight==0){
Ratio = 1;
}else if (maxWidth==0){//
if (hRatio<1) Ratio = hRatio;
}else if (maxHeight==0){
if (wRatio<1) Ratio = wRatio;
}else if (wRatio<1 || hRatio<1){
Ratio = (wRatio<=hRatio?wRatio:hRatio);
}
if (Ratio<1){
w = w * Ratio;
h = h * Ratio;
}
objImg.height = h;
objImg.width = w;
}
</script>

</head>

<body>

<img src="1111.jpg" border="0" alt="534 X 800" id="operImg"/>

<input type="button" value="缩放至宽100px，等比例压缩" onclick="AutoResizeImage(100,0)"/>

<input type="button" value="缩放至300px，等比例压缩" onclick="AutoResizeImage(300,0)"/>

<input type="button" value="原图" onclick="AutoResizeImage(0,0)"/>
</body>
</html>

重点js:
复制代码 代码如下:
function AutoResizeImage(maxWidth,maxHeight){
var objImg = document.getElementById("operImg");
var img = new Image();
img.src = objImg.src;
var hRatio;
var wRatio;
var Ratio = 1;
var w = img.width;
var h = img.height;
wRatio = maxWidth / w;
hRatio = maxHeight / h;
if (maxWidth ==0 && maxHeight==0){
Ratio = 1;
}else if (maxWidth==0){//
if (hRatio<1) Ratio = hRatio;
}else if (maxHeight==0){
if (wRatio<1) Ratio = wRatio;
}else if (wRatio<1 || hRatio<1){
Ratio = (wRatio<=hRatio?wRatio:hRatio);
}
if (Ratio<1){
w = w * Ratio;
h = h * Ratio;
}
objImg.height = h;
objImg.width = w;
}

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