PbootCMS上传图片被压缩了怎么办

'upload' => array(
'format' => 'jpg,jpeg,png,gif,xls,xlsx,doc,docx,ppt,pptx,rar,zip,pdf,txt,mp4,avi,flv,rmvb,mp3,otf,ttf',
'max\_width' => '1920',
'max\_height' => ''
),

'ico' => array(
'max_width' => '1000',
'max_height' => '1000'
),