給定一張圖片URL判斷圖片的大小和類型：FastImage

這是一個優秀 Ruby 庫FastImage通過獲取盡可能少的內容，對給定的一張圖片URI來判斷圖片的大小和類型。

特性

Fastimage還能夠讀取本地文件，使用Addressable庫來實現。

FastImage will automatically read from any object that responds to :read – for
  instance an IO object if that is passed instead of a URI.

FastImage會跟進至4 HTTP重定向來獲得圖像。

FastImage will obey the http_proxy setting in your environment to route requests via a proxy.

You can add a timeout to the request which will limit the request time by passing :timeout => number_of_seconds.

FastImage normally replies will nil if it encounters an error, but you can pass :raise_on_failure => true to get an exception.

FastImage.size("http://stephensykes.com/images/ss.com_x.gif")
=> [266, 56]  # width, height
FastImage.type("http://stephensykes.com/images/pngimage")
=> :png
FastImage.type("/some/local/file.gif")
=> :gif
FastImage.size("http://upload.wikimedia.org/wikipedia/commons/b/b4/Mardin_1350660_1350692_33_images.jpg", :raise_on_failure=>true, :timeout=>0.1)
=> FastImage::ImageFetchFailure: FastImage::ImageFetchFailure
FastImage.size("http://upload.wikimedia.org/wikipedia/commons/b/b4/Mardin_1350660_1350692_33_images.jpg", :raise_on_failure=>true, :timeout=>2.0)
=> [9545, 6623]

Python語言實現版：
https://github.com/bmuller/fastimage

用法

This assumes you have a working familiarity with Twisted.

Usage is pretty dang simple.

from fastimage import get_size
from twisted.internet import reactor

def handle(result):
    width, height = result
    print "Size: ", width, "x", height
    reactor.stop()

url = "http://stephensykes.com/images/ss.com_x.gif"
get_size(url).addCallbacks(handle)
reactor.run()

Size:  266 x 56

You can also just get the image type:

from fastimage import get_type
from twisted.internet import reactor

def handle(result):
    print "Type:", result
    reactor.stop()

url = "http://stephensykes.com/images/ss.com_x.gif"
get_type(url).addCallbacks(handle)
reactor.run()

which will poop out:

Type: gif

Right now, sizes can be deduced from gif / jpg / png. Additionally, it can detect the type (but not size) of bmp / tiff.