Serval is a QGIS plugin for raster editing. It provides convenient tools for modifying (small) raster parts and is not intended to process entire images - use Raster Calculator for this. Users can select some portions of a raster and apply one of the following modifications to selected cells:

• set a constant value, including NoData,
• apply a QGIS expression value,
• apply 3x3 low-pass filter,
• undo / redo.

Raster cell selection tools include:

• line selection with configurable width,
• polygon selection,
• loading selection from a vector map layer.

Multi-band rasters are fully supported - users can modify each band separately, or as RGB in case of 3/4-bands rasters.

Probing raster tool and drawing tool (changing single cell value) are also available.

For more details, see User Manual. The wiki page is now outdated. To be updated soon...

For editing thematic or categorical rasters, you might consider ThRasE.

Serval is a free/libre software and is licensed under the GNU General Public License.