GIMP, the GNU image manipulation program is an open source photo editor will works on both Linux and windows. GIMP has tools used for image retouching and editing, free-form drawing, resizing, cropping, photo-montages, converting between different image formats, and more specialised tasks. Animated images such as GIF and MPEG files can be created using an animation plugin.
The new version of GIMP 2.8.6 have many bug fixes and new features:

    * Saving to URIs is now possible
    * Fixed the brush spacing for drawing in any direction
    * It increased the brush patterns and clipboard in maximum to 1024*1024
    * The single-window docks can't shrink smaller than their requisition
    * The application no longer crashes when dealing with unavailable fonts
    * Close Gimp click the close button of the single-window
    * Default Colour from Gradient dymanics and tool preset have been added
    * Make sure data objects are saved when only theire name was changed
    * It allow the non-generated brushes to change there space
    * Ctrl+W for close the image windows and tabs, it not for docks
    * For round the neative value correctly, add SIGNED_ROUND()
    * GIMP_PLUGIN_DEBUG for work again after GLib changed logging
    * For transperent borders add or fix the zealous crop

Open Terminal and enter the following commands.