Pixel-art editor

 PikoPixel is a free, open-source application for drawing & editing
 pixel-art images & icons.
 .
 Features:
  * Easy to use
  * Unlimited undo
  * Supports multiple layers
  * Customizable canvas background & grid patterns
  * Hotkey-activated popup panels
  * Export upscaled images
  * Supports linear (gamma-correct) color blending
 .
 Originally a Mac app, PikoPixel runs natively on GNU/Linux by using
 the GNUstep framework.