Uncontrollable blending

[etki]

Hi!
I know project isn't actively maintained for a while, but still i hope things will change someday.
Currently, $image->draw()->dot(), at least for GD, forces color blending. This may be undesired - e.g., if i'm redrawing some kind of PNG, i may want to completely replace pixel instead of blending it with previous contents.
I guess methods like dot() should provide option (or array of options) for controlling behavior like this.

[mlocati]

With #790, when using the GD driver, you can write something like

$image->draw()->withAlphaBlending(false)->dot(...);