Setting a large image size slows down performance and consumes RAM

[AnastasiaDyadyk]

Open or create an image by setting a large size. Example: 6000 x 6000 pixels. Select the brush and use it on the image. Lines are drawn abruptly with a time delay. When you open the Task Manager, you can see that the consumption of RAM is very large.

Steps to reproduce the behavior:

1. Open / create large image
2. Using the tool

Expected Behavior: tools run smoothly, just like editing smaller images.

OS: Windows 10
Version: 1.6.7