Active layer The layer which has the editing focus. It is highlighted in the Layers Window.
Actual Size Sets the zoom level to 100%. Each pixel on the screen will correspond exactly with one pixel in the active layer.
Adjustment A per-pixel filter used to change the colorization or transparency of pixels. Also one of the paint.net menus which contains these types of filters.
Antialiasing The removal of jagged edges by subtle in-filling of intermediate pixels to even out the 'steps' between pixels.
Auto-Level An Adjustment used to equalize the range of colors in an image.
Bitmap (.bmp) An image file format. File sizes are usually large.
Brightness / Contrast An Adjustment used to make an image brighter or darker (Brightness), or to change the difference between color tones (Contrast).
Canvas The virtual area which holds the current image.
Center Image Relocate an image to the center of the editing window.
Clipboard A software facility used for short-term data storage. Stored data can be transfered between documents or applications.
Clone Stamp A tool which copies circular regions from one place to another.
Contiguous A fill mode which tests pixel neighbors and colors them according to similarity to the source pixel.
Copy Places a copy of the current layer or selection into the clipboard.
Create selection To use any of the selection tools to form a selection.
Crop to Selection Removes unselected portions of an image.
Curves An Adjustment used to adjust the luminosity and/or RGB (Red, Green & Blue) color curves of an image.
Cut Removes a region from an image after placing a copy of it on the clipboard.
Desaturate To lower the intensity of colors.
Deselect Removes the selection focus from all pixels.
Drag Click, hold and move the mouse.
Effect A tool which may alter the existing layer or create entirely new areas of color.
Ellipse Select A tool used to create elliptical and circular selections.
End Cap The shape or style used at the end of a line or curve.
Erase Selection Removes the current selection from an image.
Eraser A brush-like tool which removes color information from pixels.
File Menu One of the paint.net menus. The menu items cover saving, loading and printing of files.
Fill Selection Colors the current selection with the Primary or Secondary color.
Flatten Merge all layers into a single layer.
Global (Fill Mode) A fill mode which colors non-adjacent pixels according to similarity to the source pixel.
Global (Selection Mode) A selection mode which matches non-adjacent pixels according to similarity to the source pixel.
Gradient A tool which creates patterns transitioning from one color to another.
Greyscale A palette of colors ranging from Black to White. In paint.net there are 256 shades of gray.
Hardness A Toolbar option which determines how hard or soft the edge of a tool will be.
History Window The utility window where the editing steps are shown.
Hue A shade of color. Hue is the clock-wise angle around the rim of the color wheel (starting from red).
Hue / Saturation An Adjustment used to change the vividness of the colors in an image.
Image List An area in the Toolbar where opened images are displayed as thumbnails.
Import File Allows the selection of an existing image which is copied onto the editing surface.
Invert Selection Swaps the selection focus from any selected pixels to any unselected pixels.
JPG / JPEG (Joint Photographic Experts Group) Image file format. JPGs are superior at making photos smaller by allowing the loss of minor detail.
Keyboard shortcuts Combinations of keyboard keys which perform a particular action.
Lasso Select A tool used to create freehand selections.
Layer Properties The dialog where the layer name, blend mode, visibility and opacity can be altered.
Layers Window The utility window where a composite image's individual layers are shown.
Levels An Adjustment used to change the color range and gamma index of an image.
Magic Wand Tool A tool used to select similar pixels or regions.
Menu Bar The area above the Toolbar containing menus.
Move Selection A tool which reshapes or moves the selection outline.
Noise An Effect sub-menu. Noise Effects can be used to add or remove digital "noise" from an image. Digital noise can be likened to TV static.
Paint Bucket A tool used to fill areas with the Primary or Secondary color.
Paintbrush A tool used to create swathes in a single color or hue.
Palette A predefined list of colors. In paint.net a palette can hold 96 colors.
Pan Move an image horizontally and/or vertically.
Paste Insert the contents of the clipboard into the active layer or selection.
Pencil A tool which colors individual pixels. Useful for or drawing thin freehand lines.
PNG (Portable Network Graphics) Image file format. Lossless. Supports a full Alpha (transparency) channel.
Primary Color One of two color slots which hold a color, hue or shade for quick use.
Rasterization The collective name for antialiasing and aliasing.
Rectangle Select A tool used to create rectangular selections.
Redo Restores the last action removed with Undo.
Resize Change the dimensions of an image.
Rotate / Zoom A tool which can rotate, tilt, pan and zoom the active layer or selection.
Saturation The intensity of a color. Saturation can be thought of as the distance from the center of the color wheel to the given color.
Save Saves the current image using the existing filename and file format (where possible). Keyboard shortcut is Ctrl + S.
Save As... Saves a copy the current image by allowing a new filename, location and file format to be specified.
Secondary Color One of two color slots which hold a color, hue or shade for quick use.
Selection A grouping of pixels highlighted so that they can be processed independently of any unselected pixels.
Shapes Predefined line drawings which can be quickly added to an image.
Tolerance A numerical figure representing the similarity or dissimilarity between pixels.
Tone An alternative way of expressing the lightness or luminosity of a color.
Tool Bar An area above the editing surface where quick-use icons and tool options are shown.
Tools Window The utility window where Tools may be selected by clicking with the mouse.
Undo Reverse the last editing operation.
Zoom in / out Expand or contract the view size of an image.