The GIF as an art form—a short and silent loop—has never been more popular than it is right now. Yet the GIF as a filetype, the way we store the library of ones and zeros that computers translate into animation, is quietly embattled. Behind the scenes, a war to exterminate it has been raging for years, and it never really ended. All these years after Burn All GIFs Day, the GIF remains both deeply flawed and yet strangely irreplaceable. Whether this latest frenzy of GIF popularity enshrines it forever or kills it for good, you can be damn sure we’ll never see anything quite like it again.

Earlier this year, Twitter introduced a built-in search engine that offers split-second access to a library of thousands upon thousands of GIFs. Giphy, the company that curates that library, raised $55 million dollars in its latest round of funding, bringing its total value to some $300 million. A year before that, Imgur—until very recently the de facto image hosting service for the media mammoth Reddit and a $200 million company in its own right—rolled out GIFV, its own attempt to modernize the nearly 30-year-old file format.

• 几种图片格式简介 
• 移动端图片类型的支持情况 
  
• 静态图片的编码与解码：JPEG/PNG/WebP/BPG 
  
• 动态图片的编码与解码：GIF/APNG/WebP/BPG 
  
• 动图性能对比

Nginx 提供 ngx_http_image_filter_module 可以帮助你处理图片：

• 缩放
  
• 裁剪
  
• 调整图片品质
  
• 旋转
  
• 锐化
  

我们常用的可能就是缩放和裁剪了，根据业务和设计需要，在合适的位置不同尺寸的缩略图。

HTTP/1.1 协议规定的 HTTP 请求方法有 OPTIONS、GET、HEAD、POST、PUT、DELETE、TRACE、CONNECT 这几种。其中 POST 一般用来向服务端提交数据，本文主要讨论用 POST 提交数据的几种方式：

• application/x-www-form-urlencoded
  
• multipart/form-data
  
• application/json
  
• text/xml
  

服务端通常根据请求头（headers）中的 Content-Type 字段来获知请求中的消息主体是用何种方式编码，再对主体进行解析。所以说到 POST 提交数据方案，包含了 Content-Type 和消息主体编码方式两部分。

I initially wrote this post for myself, I wanted to understand enough about the underlying physical storage to be able to grasp other concepts which can affect your database. This post is probably more aimed to people with similar interests, I will try to keep it accurate but the aim is to make it simpler to understand so I may overlook some details.

GIF is different from many other common bitmap formats in the sense that it is stream-based. It consists of a series of data packets, called blocks, along with additional protocol information. Because of this arrangement, GIF files must be read as if they are a continuous stream of data. The various blocks and sub-blocks of data defined by GIF may be found almost anywhere within the file.

Lempel–Ziv–Welch (LZW) is a universal lossless data compression algorithm created by Abraham Lempel, Jacob Ziv, and Terry Welch. It was published by Welch in 1984 as an improved implementation of the LZ78 algorithm published by Lempel and Ziv in 1978. The algorithm is simple to implement, and has the potential for very high throughput in hardware implementations.[1] It is the algorithm of the widely used Unix file compression utility compress, and is used in the GIF image format. – Wikipedia