我有一个图像的based64编码代码。现在我想减少图像的大小和质量。我如何在JavaScript或jQuery中做到这一点？
解析如下：php这里是javascript的代码，它的工作形式我
<html>
<head>
<title>JavaScript Image Resize</title>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<style>
body {
font-size: 16px;
font-family: Arial;
}
</style>
<script type="text/javascript">
function _resize(img, maxWidth, maxHeight)
{
var ratio = 1;
var canvas = document.createElement("canvas");
canvas.style.display="none";
document.body.appendChild(canvas);
var canvasCopy = document.createElement("canvas");
canvasCopy.style.display="none";
document.body.appendChild(canvasCopy);
var ctx = canvas.getContext("2d");
var copyContext = canvasCopy.getContext("2d");
if(img.width > maxWidth)
ratio = maxWidth / img.width;
else if(img.height > maxHeight)
ratio = maxHeight / img.height;
canvasCopy.width = img.width;
canvasCopy.height = img.height;
try {
copyContext.drawImage(img, 0, 0);
} catch (e) {
document.getElementById('loader').style.display="none";
alert("There was a problem - please reupload your image");
return false;
}
canvas.width = img.width * ratio;
canvas.height = img.height * ratio;
// the line to change
//ctx.drawImage(canvasCopy, 0, 0, canvasCopy.width, canvasCopy.height, 0, 0, canvas.width, canvas.height);
// the method signature you are using is for slicing
ctx.drawImage(canvasCopy, 0, 0, canvas.width, canvas.height);
var dataURL = canvas.toDataURL("image/png");
document.body.removeChild(canvas);
document.body.removeChild(canvasCopy);
return dataURL.replace(/^data:image\/(png|jpg);base64,/, "");
};
function resize() {
var photo = document.getElementById("photo");
if(photo.files!=undefined){
var loader = document.getElementById("loader");
loader.style.display = "inline";
var file = photo.files[0];
document.getElementById("orig").value = file.fileSize;
var preview = document.getElementById("preview");
var r = new FileReader();
r.onload = (function(previewImage) {
return function(e) {
var maxx = 500;
var maxy = 500;
previewImage.src = e.target.result;
var k = _resize(previewImage, maxx, maxy);
if(k!=false) {
document.getElementById('base64').value= k;
document.getElementById('upload').submit();
} else {
alert('problem - please attempt to upload again');
}
};
})(preview);
r.readAsDataURL(file);
} else {
alert("Seems your browser doesn't support resizing");
}
return false;
}
</script>
</head>
<body>
<div align="center">
<h2>Image Resize Demo</h2>
<input type="file" name="photo" id="photo">
<br>
<br>
<input type="button" onClick="resize();" value="Resize">
<img src="loader.gif" id="loader" />
<img src="" alt="Image preview" id="preview">
<form name="upload" id="upload" method='post' action='show.php'>
<textarea name="base64" id="base64" rows='10' cols='90'></textarea>
<input type="hidden" id="orig" name="orig" value=""/>
</form>
</div>
</body>
</html>显示.php文件
<html>
<head>
<title>JavaScript file upload</title>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<style>
body {
font-size: 16px;
font-family: Arial;
}
#preview {
display:none;
}
#base64 {
display:none;
}
</style>
</head>
<body>
<?php
$base64size = strlen($_POST['base64']);
$f = base64_decode($_POST['base64']);
$name = microtime(true).".png";
file_put_contents("./$name", $f);
#header("Content-type: image/png");
#header("Content-Disposition: attachment; filename=\"shrunk.png\"");
#echo $f;
#die();
?>
<h2>Shrunk file</h2>
<p>Original file was: <?=$_POST['orig'];?> bytes</p>
<p>Transmitted size was: <?=$base64size;?> bytes (due to base64)</p>
<p>New file is: <?=filesize("./$name");?> bytes</p>
<p><img src="<?=$name;?>"/></p>
</body>
</html>
3条答案
按热度按时间bjp0bcyl1#
你可以使用canvas，把图片放进去，缩放它，用新的base64代码获取图片源。
下面是这样做的函数，它返回promise对象，因为在绘制画布并获取其编码的src之前，需要首先加载（缓存）图像。
可以这样使用：
这里是jsfiddle
w1jd8yoj2#
一个基于@paulitto的答案的非jquery解决方案，适用于像我这样的未来谷歌人：
像这样使用它：
注意，这个函数返回一个base64字符串。要获取
<img>，可以使用以下命令示例：
9bfwbjaz3#
这是一个改进的typescript pro版本。