composer安装了不能用，是需要配置什么吗，去git上也看不到

不用改多少代码；把上述文件复制到对应的目录；只需要在vendor/yiisoft/extensions.php增加这2个引入就可以

  'yiisoft/yii2-imagine' => 
  array (
    'name' => 'yiisoft/yii2-imagine',
    'version' => '2.0.3.0',
    'alias' => 
    array (
      '@yii/imagine' => $vendorDir . '/yiisoft/yii2-imagine',
    ),
  ),
  'yiisoft/Imagine' => 
  array (
    'name' => 'yiisoft/Imagine',
    'version' => '5.0.0.0',
    'alias' => 
    array (
	  '@Imagine' => $vendorDir . '/imagine',
    ),
  ),