Resizing image into thumbnail, small, medium and large options greyed out

by

it can be caused by multiple reasons , some of which may be :

  • theme disabling this function

=> switch to default theme and check function again

  • GD library not installed on server

=> check your PHP server settings .

  • the image you are inserting is smaller than the thumbnail image size
    set in Admin/Settings/Media.

=> check your default image sizes and / or upload a bigger image

  • some plugin is causing it

=> disable all plugins and check function again.

  • Defected image

=> Try another image

  • Max file upload restriction

=> In functions.php

 @ini_set( 'upload_max_size' , '64M' );
@ini_set( 'post_max_size', '64M');
@ini_set( 'max_execution_time', '300' );