Add this below code in function.php fle
add_filter( 'wp_image_editors', 'change_graphic_lib' );
function change_graphic_lib($array) {
return array( 'WP_Image_Editor_GD', 'WP_Image_Editor_Imagick' );
}
If above code is not work , follow below steps to remove error
1. Decrease the image’s size. Don’t add a 2000 x 1500 image, for example. If your post content area is 700px wide, don’t add an image larger than that.
2. Change the image’s extension from .png to .jpg, or vice versa, then upload it again.
3. If the problem appears after installing a plugin, deactivate it and try it again. Some plugins can trigger the error.
4. Increase your PHP memory. Add this code define(‘WP_MEMORY_LIMIT’, ’64M’) into your wp-config.php file. This setting may not work if your host does not allow you to increase the PHP memory limit, so I suggest talking to your support directly and ask them to change the limit for you. You’ll skip the hassle.
Read this guide if you need to know how to access and edit your WordPress files.
5. Add one of these codes in .htaccess:
<IfModule mod_security.c>
SecFilterEngine Off
SecFilterScanPOST Off
</IfModule>
or
# Exclude the file upload and WP CRON scripts from authentication
<FilesMatch "(async-upload\.php|wp-cron\.php|xmlrpc\.php)$">
Satisfy Any
Order allow,deny
Allow from all
Deny from none
</FilesMatch>
or
AddType x-mapp-php5 .php (at the very top of your .htaccess file)
