yiisoft/yii2 — pull request #1138 by nukkumatti (2013-11-05 00:19:11+00:00)
Title: Proposal for #827 Add ImageValidator

I can make it without extending FileValidator.
But there are uploadRequired, tooMany, tooBig checks in FileValidator and I think it would be a wasted try to check image's sizes when an uploaded file is tooBig or not even uploaded.