Javascript 上传前使用HTML5调整图像大小
我发现了一些不同的帖子,甚至有关于stackoverflow的问题来回答这个问题。我基本上实现了与之相同的事情 这就是我的问题。当我上传照片时,我还需要提交表单的其余部分。这是我的html:Javascript 上传前使用HTML5调整图像大小,javascript,html,canvas,Javascript,Html,Canvas,我发现了一些不同的帖子,甚至有关于stackoverflow的问题来回答这个问题。我基本上实现了与之相同的事情 这就是我的问题。当我上传照片时,我还需要提交表单的其余部分。这是我的html: <form id="uploadImageForm" enctype="multipart/form-data"> <input name="imagefile[]" type="file" id="takePictureField" accept="image/*" onchange
<form id="uploadImageForm" enctype="multipart/form-data">
<input name="imagefile[]" type="file" id="takePictureField" accept="image/*" onchange="uploadPhotos(\'#{imageUploadUrl}\')" />
<input id="name" value="#{name}" />
... a few more inputs ...
</form>
这一切都很有效。。。现在我需要调整图像的大小。。。如何替换表单中的图像,以便发布调整大小的图像而不是上载的图像
window.uploadPhotos = function(url){
var resizedImage;
// Read in file
var file = event.target.files[0];
// Ensure it's an image
if(file.type.match(/image.*/)) {
console.log('An image has been loaded');
// Load the image
var reader = new FileReader();
reader.onload = function (readerEvent) {
var image = new Image();
image.onload = function (imageEvent) {
// Resize the image
var canvas = document.createElement('canvas'),
max_size = 1200,
width = image.width,
height = image.height;
if (width > height) {
if (width > max_size) {
height *= max_size / width;
width = max_size;
}
} else {
if (height > max_size) {
width *= max_size / height;
height = max_size;
}
}
canvas.width = width;
canvas.height = height;
canvas.getContext('2d').drawImage(image, 0, 0, width, height);
resizedImage = canvas.toDataURL('image/jpeg');
}
image.src = readerEvent.target.result;
}
reader.readAsDataURL(file);
}
// TODO: Need some logic here to switch out which photo is being posted...
var data = new FormData($("form[id*='uploadImageForm']")[0]);
$.ajax({
url: url,
data: data,
cache: false,
contentType: false,
processData: false,
type: 'POST',
success: function(data){
... handle error...
}
}
});
};
我考虑过将文件输入移出表单,并在表单中设置一个隐藏的输入,将值设置为调整大小后的图像的值。。。但是我想知道我是否可以替换表单中已经存在的图像。这是我最后做的事情,效果非常好 首先,我将文件输入移到表单之外,以便不提交:
<input name="imagefile[]" type="file" id="takePictureField" accept="image/*" onchange="uploadPhotos(\'#{imageUploadUrl}\')" />
<form id="uploadImageForm" enctype="multipart/form-data">
<input id="name" value="#{name}" />
... a few more inputs ...
</form>
如您所见,我使用的是canvas.toDataURL('image/jpeg')
将调整大小的图像更改为dataUrl adn,然后调用函数dataURLToBlob(dataUrl)
将dataUrl转换为blob,然后可以将其附加到表单中。创建blob时,我触发一个自定义事件。以下是创建blob的函数:
/* Utility function to convert a canvas to a BLOB */
var dataURLToBlob = function(dataURL) {
var BASE64_MARKER = ';base64,';
if (dataURL.indexOf(BASE64_MARKER) == -1) {
var parts = dataURL.split(',');
var contentType = parts[0].split(':')[1];
var raw = parts[1];
return new Blob([raw], {type: contentType});
}
var parts = dataURL.split(BASE64_MARKER);
var contentType = parts[0].split(':')[1];
var raw = window.atob(parts[1]);
var rawLength = raw.length;
var uInt8Array = new Uint8Array(rawLength);
for (var i = 0; i < rawLength; ++i) {
uInt8Array[i] = raw.charCodeAt(i);
}
return new Blob([uInt8Array], {type: contentType});
}
/* End Utility function to convert a canvas to a BLOB */
如果有人感兴趣,我已经制作了一个打字脚本版本:
interface IResizeImageOptions {
maxSize: number;
file: File;
}
const resizeImage = (settings: IResizeImageOptions) => {
const file = settings.file;
const maxSize = settings.maxSize;
const reader = new FileReader();
const image = new Image();
const canvas = document.createElement('canvas');
const dataURItoBlob = (dataURI: string) => {
const bytes = dataURI.split(',')[0].indexOf('base64') >= 0 ?
atob(dataURI.split(',')[1]) :
unescape(dataURI.split(',')[1]);
const mime = dataURI.split(',')[0].split(':')[1].split(';')[0];
const max = bytes.length;
const ia = new Uint8Array(max);
for (var i = 0; i < max; i++) ia[i] = bytes.charCodeAt(i);
return new Blob([ia], {type:mime});
};
const resize = () => {
let width = image.width;
let height = image.height;
if (width > height) {
if (width > maxSize) {
height *= maxSize / width;
width = maxSize;
}
} else {
if (height > maxSize) {
width *= maxSize / height;
height = maxSize;
}
}
canvas.width = width;
canvas.height = height;
canvas.getContext('2d').drawImage(image, 0, 0, width, height);
let dataUrl = canvas.toDataURL('image/jpeg');
return dataURItoBlob(dataUrl);
};
return new Promise((ok, no) => {
if (!file.type.match(/image.*/)) {
no(new Error("Not an image"));
return;
}
reader.onload = (readerEvent: any) => {
image.onload = () => ok(resize());
image.src = readerEvent.target.result;
};
reader.readAsDataURL(file);
})
};
或(async
/wait
):
如果你们中的一些人,像我一样,遇到定向问题,我将这里的解决方案与exif定向修复结合起来
您使用的是服务器端语言还是html5和javascript?@luke2012 java服务器端可能会使用类似jCrop的东西在客户端裁剪图像,然后将坐标发送到服务器端并进行裁剪。i、 e
BufferedImage dest=src.getSubimage(rect.x、rect.y、rect.width、rect.height)
@luke2012关键是在将图像发送到服务器之前减小图像大小。看看的js源代码似乎很相似。非常好的代码,经过一些调整和修复一些错误(我不记得确切是什么和哪个)后,我让它工作了。顺便说一下,我想当你写width*=max\u size/width代码>你实际上是指宽度*=最大尺寸/高度代码>。此代码在移动设备上有效吗?在iOS和Android下?@planewalker,我实际上是专门为移动设备编写代码的。为了减少数据使用量,我写这篇文章的时候正在iOS上测试。希望它对你有用。做得好,谢谢分享!(其他人提到但未识别的小错误是在图像大小调整事件触发器中。“url:url”应该是“url:dataUrl”)非常好的解决方案,可能是添加一个额外的设置以允许将结果返回为base64(在末尾绕过dataURIToBlob调用)。我得到这个错误:Uncaught(承诺中)TypeError:无法读取未定义的属性“type”
Nice。我必须将unescape更改为(窗口)。unescape我还添加了minSize。maxSize
的单位是字节还是kb?您的回答帮助我回答了,谢谢。
/* Utility function to convert a canvas to a BLOB */
var dataURLToBlob = function(dataURL) {
var BASE64_MARKER = ';base64,';
if (dataURL.indexOf(BASE64_MARKER) == -1) {
var parts = dataURL.split(',');
var contentType = parts[0].split(':')[1];
var raw = parts[1];
return new Blob([raw], {type: contentType});
}
var parts = dataURL.split(BASE64_MARKER);
var contentType = parts[0].split(':')[1];
var raw = window.atob(parts[1]);
var rawLength = raw.length;
var uInt8Array = new Uint8Array(rawLength);
for (var i = 0; i < rawLength; ++i) {
uInt8Array[i] = raw.charCodeAt(i);
}
return new Blob([uInt8Array], {type: contentType});
}
/* End Utility function to convert a canvas to a BLOB */
/* Handle image resized events */
$(document).on("imageResized", function (event) {
var data = new FormData($("form[id*='uploadImageForm']")[0]);
if (event.blob && event.url) {
data.append('image_data', event.blob);
$.ajax({
url: event.url,
data: data,
cache: false,
contentType: false,
processData: false,
type: 'POST',
success: function(data){
//handle errors...
}
});
}
});
interface IResizeImageOptions {
maxSize: number;
file: File;
}
const resizeImage = (settings: IResizeImageOptions) => {
const file = settings.file;
const maxSize = settings.maxSize;
const reader = new FileReader();
const image = new Image();
const canvas = document.createElement('canvas');
const dataURItoBlob = (dataURI: string) => {
const bytes = dataURI.split(',')[0].indexOf('base64') >= 0 ?
atob(dataURI.split(',')[1]) :
unescape(dataURI.split(',')[1]);
const mime = dataURI.split(',')[0].split(':')[1].split(';')[0];
const max = bytes.length;
const ia = new Uint8Array(max);
for (var i = 0; i < max; i++) ia[i] = bytes.charCodeAt(i);
return new Blob([ia], {type:mime});
};
const resize = () => {
let width = image.width;
let height = image.height;
if (width > height) {
if (width > maxSize) {
height *= maxSize / width;
width = maxSize;
}
} else {
if (height > maxSize) {
width *= maxSize / height;
height = maxSize;
}
}
canvas.width = width;
canvas.height = height;
canvas.getContext('2d').drawImage(image, 0, 0, width, height);
let dataUrl = canvas.toDataURL('image/jpeg');
return dataURItoBlob(dataUrl);
};
return new Promise((ok, no) => {
if (!file.type.match(/image.*/)) {
no(new Error("Not an image"));
return;
}
reader.onload = (readerEvent: any) => {
image.onload = () => ok(resize());
image.src = readerEvent.target.result;
};
reader.readAsDataURL(file);
})
};
var resizeImage = function (settings) {
var file = settings.file;
var maxSize = settings.maxSize;
var reader = new FileReader();
var image = new Image();
var canvas = document.createElement('canvas');
var dataURItoBlob = function (dataURI) {
var bytes = dataURI.split(',')[0].indexOf('base64') >= 0 ?
atob(dataURI.split(',')[1]) :
unescape(dataURI.split(',')[1]);
var mime = dataURI.split(',')[0].split(':')[1].split(';')[0];
var max = bytes.length;
var ia = new Uint8Array(max);
for (var i = 0; i < max; i++)
ia[i] = bytes.charCodeAt(i);
return new Blob([ia], { type: mime });
};
var resize = function () {
var width = image.width;
var height = image.height;
if (width > height) {
if (width > maxSize) {
height *= maxSize / width;
width = maxSize;
}
} else {
if (height > maxSize) {
width *= maxSize / height;
height = maxSize;
}
}
canvas.width = width;
canvas.height = height;
canvas.getContext('2d').drawImage(image, 0, 0, width, height);
var dataUrl = canvas.toDataURL('image/jpeg');
return dataURItoBlob(dataUrl);
};
return new Promise(function (ok, no) {
if (!file.type.match(/image.*/)) {
no(new Error("Not an image"));
return;
}
reader.onload = function (readerEvent) {
image.onload = function () { return ok(resize()); };
image.src = readerEvent.target.result;
};
reader.readAsDataURL(file);
});
};
resizeImage({
file: $image.files[0],
maxSize: 500
}).then(function (resizedImage) {
console.log("upload resized image")
}).catch(function (err) {
console.error(err);
});
const config = {
file: $image.files[0],
maxSize: 500
};
const resizedImage = await resizeImage(config)
console.log("upload resized image")