在windows上执行composer update，用到了intervention/image这个包，执行过程中提示推荐安装两个包：

intervention/image suggests installing ext-imagick (to use Imagick based image p                                                                              rocessing.)
intervention/image suggests installing intervention/imagecache (Caching extensio                                                                              n for the Intervention Image library)

关于这两个包有3个疑问：
1、两个包分别是干什么的？
2、第1个包在github上找不到，那么在哪里下载？
3、第2个包可以在github上找到，但好久没更新了，过时了没有？

附：命令执行时完整信息：

dell@DESKTOP-MVU77SM MINGW64 /d/wnmp/www/laravel-5-3-demo
$ composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
  - Installing psr/http-message (1.0.1)
    Downloading: 100%

  - Installing guzzlehttp/psr7 (1.3.1)
    Downloading: 100%

  - Installing intervention/image (dev-master 6886d43)
    Downloading: 100%

  - Installing laravelcollective/html (dev-master c4c8791)
    Downloading: 100%

  - Installing adambrett/shell-wrapper (dev-master d1fb1a6)
    Downloading: 100%

  - Removing laravel/framework (5.3.x-dev bd9cd77)
  - Installing laravel/framework (5.3.x-dev 12336ad)
    Downloading: 100%

intervention/image suggests installing ext-imagick (to use Imagick based image p                                                                              rocessing.)
intervention/image suggests installing intervention/imagecache (Caching extensio                                                                              n for the Intervention Image library)
Writing lock file
Generating autoload files
> Illuminate\Foundation\ComposerScripts::postUpdate
> php artisan optimize
Generating optimized class loader