javascript - 图像未定义
问题描述
我已经阅读了很多类似的错误但仍然找不到解决方案,这是我的第一个 js 和写作,我想从我的驱动器中读取一个图像文件并调整它的大小,但只是我的第一行代码给了我错误,谢谢
var img = new Image();
但我得到这个 ReferenceError: Image is not defined 任何帮助
解决方案
这是一个如何将图像上传到服务器的示例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="x-ua-compatible" content="ie=edge">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<title>Cropper.js</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.2/css/bootstrap.min.css">
<link rel="stylesheet" href="https://raw.githubusercontent.com/fengyuanchen/cropperjs/master/docs/css/cropper.css">
<style>
.label {
cursor: pointer;
}
.progress {
display: none;
margin-bottom: 1rem;
}
.alert {
display: none;
}
.img-container img {
max-width: 100%;
}
</style>
</head>
<body>
<div class="container">
<h1>Upload cropped image to server</h1>
<label class="label" data-toggle="tooltip" title="Change your avatar">
<img class="rounded" id="avatar" src="https://avatars0.githubusercontent.com/u/3456749?s=160" alt="avatar">
<input type="file" class="sr-only" id="input" name="image" accept="image/*">
</label>
<div class="progress">
<div class="progress-bar progress-bar-striped progress-bar-animated" role="progressbar" aria-valuenow="0" aria-valuemin="0" aria-valuemax="100">0%</div>
</div>
<div class="alert" role="alert"></div>
<div class="modal fade" id="modal" tabindex="-1" role="dialog" aria-labelledby="modalLabel" aria-hidden="true">
<div class="modal-dialog" role="document">
<div class="modal-content">
<div class="modal-header">
<h5 class="modal-title" id="modalLabel">Crop the image</h5>
<button type="button" class="close" data-dismiss="modal" aria-label="Close">
<span aria-hidden="true">×</span>
</button>
</div>
<div class="modal-body">
<div class="img-container">
<img id="image" src="https://avatars0.githubusercontent.com/u/3456749">
</div>
</div>
<div class="modal-footer">
<button type="button" class="btn btn-secondary" data-dismiss="modal">Cancel</button>
<button type="button" class="btn btn-primary" id="crop">Crop</button>
</div>
</div>
</div>
</div>
</div>
<script src="https://code.jquery.com/jquery-3.4.1.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.2/js/bootstrap.bundle.min.js"></script>
<script src="https://raw.githubusercontent.com/fengyuanchen/cropperjs/master/docs/js/cropper.js"></script>
<script>
window.addEventListener('DOMContentLoaded', function () {
var avatar = document.getElementById('avatar');
var image = document.getElementById('image');
var input = document.getElementById('input');
var $progress = $('.progress');
var $progressBar = $('.progress-bar');
var $alert = $('.alert');
var $modal = $('#modal');
var cropper;
$('[data-toggle="tooltip"]').tooltip();
input.addEventListener('change', function (e) {
var files = e.target.files;
var done = function (url) {
input.value = '';
image.src = url;
$alert.hide();
$modal.modal('show');
};
var reader;
var file;
var url;
if (files && files.length > 0) {
file = files[0];
if (URL) {
done(URL.createObjectURL(file));
} else if (FileReader) {
reader = new FileReader();
reader.onload = function (e) {
done(reader.result);
};
reader.readAsDataURL(file);
}
}
});
$modal.on('shown.bs.modal', function () {
cropper = new Cropper(image, {
aspectRatio: 1,
viewMode: 3,
});
}).on('hidden.bs.modal', function () {
cropper.destroy();
cropper = null;
});
document.getElementById('crop').addEventListener('click', function () {
var initialAvatarURL;
var canvas;
$modal.modal('hide');
if (cropper) {
canvas = cropper.getCroppedCanvas({
width: 160,
height: 160,
});
initialAvatarURL = avatar.src;
avatar.src = canvas.toDataURL();
$progress.show();
$alert.removeClass('alert-success alert-warning');
canvas.toBlob(function (blob) {
var formData = new FormData();
formData.append('avatar', blob, 'avatar.jpg');
$.ajax('https://jsonplaceholder.typicode.com/posts', {
method: 'POST',
data: formData,
processData: false,
contentType: false,
xhr: function () {
var xhr = new XMLHttpRequest();
xhr.upload.onprogress = function (e) {
var percent = '0';
var percentage = '0%';
if (e.lengthComputable) {
percent = Math.round((e.loaded / e.total) * 100);
percentage = percent + '%';
$progressBar.width(percentage).attr('aria-valuenow', percent).text(percentage);
}
};
return xhr;
},
success: function () {
$alert.show().addClass('alert-success').text('Upload success');
},
error: function () {
avatar.src = initialAvatarURL;
$alert.show().addClass('alert-warning').text('Upload error');
},
complete: function () {
$progress.hide();
},
});
});
}
});
});
</script>
</body>
</html>
在 ajax 调用中,它将图像发布到后端,以便您处理它
$.ajax('postimage.php', {
method: 'POST',
data: formData,
processData: false,
contentType: false,
您还需要定义图像路径
var img = new Image("path/to/image.jpg");
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