Magento 2 – imagecolorsforindex() Argument Out of Range Error

Please try to remove all the directories inside var/generation folder and then run following command :

php bin/magento cache:flush

After that run your command you will be succeed.

Simple, try the following commands. I have encountered this error, and I have overcome.

rm -rf var/di/* 
rm -rf pub/static/_cache/* 
rm -rf pub/static/frontend/*
rm -rf var/generation/* 
rm -rf var/cache/*
rm -rf var/page_cache/*
rm -rf var/view_preprocessed/*

In magento 2

var/di has been replaced by generated/metadata

var/generation has been replaced by generated/code

I switched to Developer Mode, and deleted the below files.

rm -rf generated/metadata/* 
rm -rf pub/static/_cache/* 
rm -rf pub/static/frontend/*
rm -rf generated/code/* 
rm -rf var/cache/*
rm -rf var/page_cache/*
rm -rf var/view_preprocessed/*

never delete pub/static/.htaccess. putting star *at the end does not delete .htaccess file in the folder.

you may also need to run setup di compile to optimize and regenerate magento2 file system.

bin/magento setup:di:compile
bin/magento indexer:reindex