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js中关于Blob对象的介绍与使用

由 一个人想着一个人 提交于 2019-12-29 08:31:56
blob对象介绍 一个 Blob对象表示一个不可变的, 原始数据的类似文件对象。Blob表示的数据不一定是一个JavaScript原生格式 blob对象本质上是js中的一个对象，里面可以储存大量的二进制编码格式的数据。 创建blob对象 创建blob对象本质上和创建一个其他对象的方式是一样的，都是使用Blob() 的构造函数来进行创建。 构造函数接受两个参数： 第一个参数为一个数据序列，可以是任意格式的值。 第二个参数是一个包含两个属性的对象{ type: MIME的类型, endings: 决定第一个参数的数据格式，可以取值为 "transparent" 或者 "native"（transparent的话不变，是默认值，native 的话按操作系统转换） 。 } Blob()构造函数允许使用其他对象创建一个Blob对象，比如用字符串构建一个blob var debug = {hello: "world"}; var blob = new Blob([JSON.stringify(debug, null, 2)], {type : 'application/json'}); 既然是对象，那么blob也拥有自己的属性以及方法 属性 Blob.isClosed (只读) 布尔值，指示 Blob.close() 是否在该对象上调用过。 关闭的 blob 对象不可读。 Blob.size

How to display mysql blob image in asp.net image control?

由 随声附和 提交于 2019-12-29 08:10:49
问题 I known the way to display the mysql blob image in Windows Forms. try { MySqlConnection connection = new MySqlConnection(hp.myConnStr); MySqlCommand command = connection.CreateCommand(); MySqlDataReader Reader; command.CommandText = "select logo from mcs_institude where id = 1"; connection.Open(); Reader = command.ExecuteReader(); while (Reader.Read()) { pictureBox1.Image = new Bitmap(new MemoryStream((byte[])Reader.GetValue(0))); } connection.Close(); } catch(Exception ex) { MessageBox.Show(

Displaying Blob Images in Python (App Engine)

由 回眸只為那壹抹淺笑 提交于 2019-12-29 07:51:48
问题 I am unable to get the image to display on the page. I can store it just fine. These are the handlers: class disp_image(webapp.RequestHandler): def get(self): key = self.request.get('key') image = Images.get(key) if image: self.response.headers['Content-Type'] = "image/png" return self.response.out.write(images.image) else: self.response.headers['Content-Type'] = "image/png" return self.response.out.write("/static/unknown.gif") class Profile(MainHandler): def get(self): if self.user: self

How to stream data to database BLOB using Hibernate (no in-memory storing in byte[])

由 放肆的年华 提交于 2019-12-29 04:07:08
问题 I'm looking for a way to stream binary data to/from database. If possible, i'd like it to be done with Hibernate (in database agnostic way). All solutions I've found involve explicit or implicit loading of binary data into memory as byte[]. I need to avoid it. Let's say I want my code to be able to write to a local file a 2GB video from database (stored in BLOB column), or the other way around, using no more than 256Mb of memory. It's clearly achievable, and involves no voodoo. But I can't

Is it possible to perform a batch upload to amazon s3?

由 徘徊边缘 提交于 2019-12-29 02:47:49
问题 Does amazon s3 support batch uploads? I have a job that needs to upload each night ~100K of files that can be up to 1G but is strongly skewed towards small files (90% are less than 100 bytes and 99% are less than 1000 bytes long). Does the s3 API support uploading multiple objects in a single HTTP call? All the objects must be available in S3 as individual objects. I cannot host them anywhere else (FTP, etc) or in another format (Database, EC2 local drive, etc). That is an external

Remote image file to sqlite blob in PHP?

由 ↘锁芯ラ 提交于 2019-12-29 00:45:09
问题 I have an image file stored on a remote server. I only have HTTP access to the server, so I'm getting its content using file_get_contents(URL) I need to store this content in a local sqlite3 database in a field of type 'blob'. I'm using the PDO object to connect to the database, and I'm using $db->exec("INSERT INTO myTable (myImageBlob) VALUES ('".file_get_contents($filePath)."')") to add data to the database. This isn't working. Apologies if I'm making a really noobish mistake. We all have

Storing very large integers in MySQL

由 杀马特。学长 韩版系。学妹 提交于 2019-12-28 15:09:27
问题 I need to store a very large number (tens of millions) of 512-bit SHA-2 hashes in a MySQL table. To save space, I'd like to store them in binary form, rather than a string a hex digits. I'm using an ORM (DBix::Class) so the specific details of the storage will be abstracted from the code, which can inflate them to any object or structure that I choose. MySQL's BIGINT type is 64 bits. So I could theoretically split the hash up amongst eight BIGINT columns. That seems pretty ridiculous though.

Storing long binary (raw data) strings

由 风流意气都作罢 提交于 2019-12-28 04:27:03
问题 We are capturing a raw binary string that is variable in size (from 100k to 800k) and we would like to store these individual strings. They do not need to be indexed (duh) and there will be no queries on the contents of the field. The quantity of these inserts will be very large (they are for archival purposes), let's say 10,000 per day. What is the best field type for large binary strings like these? Should it be text or blob or something else? 回答1: As far as PostgreSQL is concerned, type

HTML5 File API downloading file from server and saving it in sandbox

由 假如想象 提交于 2019-12-28 03:19:06
问题 I'm trying to understand HTML5 API. I'm designing the web application where the browser client need to download multiple files from server; user will perform something with the downloaded files and the application than need to save the state on user hard-rive. I understand that the browser can save these files only to its sandbox which is fine as long as the user can retrieve those files on the second time he starts the application. Should I use BlobBuilder or FileSaver? I'm a bit lost here.

PHP/PDO/MySQL: inserting into MEDIUMBLOB stores bad data

由 和自甴很熟 提交于 2019-12-28 03:10:33
问题 I have a simple PHP web app that accepts icon images via file upload and stores them in a MEDIUMBLOB column. On my machine (Windows) plus two Linux servers, this works fine. On a third Linux server, the inserted image is corrupted: unreadable after a SELECT, and the length of the column data as reported by the MySQL length() function is about 40% larger than the size of the uploaded file. (Each server connects to a separate instance of MySQL.) Of course, this leads me to think about encoding
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