I guess you are trying direct access.
in
You will find the chmod constants.
Keep in mind that the user is 'www-data' (generaly), wich correspond the the PHP user.
So if you are accessing with a indirect access (such as cook does), there isn't any problem.
If you want to access directly, then you have to dig a little bit.
I cannot answer you precisely, because even for me many times I get confused, and also because it is a part of my code I do not remember well.
I will have a look soon, when I will rewrite some missings features :
- Cook will propose 3 different ways to acces files (direct, indirect, Database index)
- JImage class (rewrite the cook proposed class)
- Fix the issue that cook block you to read files within the root of your Joomla. (security, but annoying)
I cannot help you more at the moment.
All contributions from users are welcome.