Krita for Beginners: Selections and Masks for Precise Editing

What selections and masks are (and why they matter)

A selection is a temporary boundary that limits where edits can happen. Anything you paint, erase, fill, transform, or filter will affect only the selected area. A mask is a reusable, non-destructive way to control visibility or effects over time. In practice, you often use selections to create or refine masks.

Think of it as two stages: select (define the area) and mask (keep control of that area for later changes).

Key selection behaviors you must control

• Add / Subtract / Intersect: build complex selections from simple shapes.
• Feather: soften selection edges for smoother blends.
• Invert: switch between selecting the subject and selecting the background.
• Deselect: remove the selection boundary so you don’t accidentally edit only part of your artwork.

Selection tools, progressively

1) Rectangular and Elliptical selections (fast, clean shapes)

Use these when the area is geometric (a panel, a face highlight, a button, a simple shadow block).

• Choose Rectangular Selection or Elliptical Selection.
• Drag to create the selection.
• To add another shape: hold the tool’s Add mode (or use the modifier shown in Krita’s tool options).
• To subtract: switch to Subtract mode and drag over the part you want removed.
• To intersect: switch to Intersect mode to keep only the overlap.

Practical example: Select a character’s eye highlight with an ellipse, then subtract a smaller ellipse to create a crescent highlight shape before filling it with a soft color.

2) Freehand / Lasso selection (organic shapes)

Use this for silhouettes, hair masses, clothing edges, and any irregular contour.

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• Choose Freehand Selection (lasso).
• Draw around the shape; close the loop to complete the selection.
• Build it in pieces: lasso a large area first, then add smaller sections (like hair tufts), and subtract mistakes.

Tip: If your hand is shaky, zoom in and lasso in shorter segments. It’s often faster to correct with subtract/add than to try to draw a perfect outline in one pass.

3) Contiguous selection (Magic Wand behavior)

This selects neighboring pixels that are similar in color/value. It’s ideal for flat-color areas, line-art gaps, or quick background removal when the background is uniform.

• Choose Contiguous Selection Tool.
• Click an area to select connected pixels of similar color.
• Adjust Threshold (tolerance): higher selects a wider range; lower is stricter.
• Enable/disable options like selecting from the current layer vs. multiple layers depending on your artwork setup.

Practical example: If your character is on a flat gray background, click the background with contiguous selection, then invert the selection to get the character.

4) Color-based selection (select all pixels of a color)

Color-based selection is useful when the same color appears in multiple disconnected places (for example, selecting all red accents across the illustration).

• Choose a Color-based Selection tool (name may vary depending on workspace/toolbox configuration).
• Click the target color; adjust tolerance to include near-matches.
• Use Add mode to include additional shades (e.g., shadowed red and lit red).

Practical example: Select all pixels of a character’s jacket base color across folds and separate shapes, then shift the hue slightly without affecting skin or hair.

Selection workflows: add, subtract, intersect, invert, feather

Building a complex selection (recommended workflow)

• Start broad: select the main mass (rectangle/ellipse for big blocks, lasso for silhouette).
• Refine: subtract obvious background intrusions; add missing parts.
• Check edges: zoom in and look for stair-stepping or holes.
• Feather only when needed: keep hard edges for cel/graphic styles; feather for soft shading and atmospheric blends.

Feathering (softening edges)

Feathering creates a gradual transition at the selection boundary. Use it for soft shadows, glow effects, and gentle color corrections.

• Apply a small feather radius for subtle softness.
• Use larger feathering for broad lighting changes.

Rule of thumb: If you can clearly see a blurry halo, your feather is probably too large for the scale of the artwork.

Invert and grow/shrink (edge control)

Two common edge fixes:

• Invert the selection to work on the opposite region (subject vs. background).
• Grow/Shrink the selection slightly to avoid halos (shrink often helps when you’re masking a character against a background).

Transforming selections and layers (scale, rotate, warp)

Transform tools let you reposition or reshape content. You can transform either a selected region or an entire layer. The key is knowing what is actually being transformed.

Transform a selected area (local edits)

• Make a selection around the part you want to change (e.g., a hand, an accessory).
• Use the Transform Tool.
• Apply Scale to resize, Rotate to adjust angle, or Warp to bend/reshape.
• Confirm/apply the transform when satisfied.

Practical example: Select a character’s hat brim and slightly warp it to match the head perspective without repainting.

Transform a whole layer (global edits)

• Click the target layer in the layer stack.
• Ensure there is no active selection if you want the entire layer affected.
• Use Transform to scale/rotate the whole element (like moving a character to improve composition).

Important: If you forget you still have a selection active, your transform may affect only part of the layer, creating seams or unexpected cut lines.

Masks for non-destructive control

Transparency masks (hide/reveal without erasing)

A transparency mask controls a layer’s visibility using grayscale values: white reveals, black hides, and gray partially hides. This is the non-destructive alternative to erasing.

How to create and use a transparency mask

• Select the layer you want to mask (for example, your character paint layer).
• Add a Transparency Mask to that layer.
• Paint on the mask with black to hide, white to reveal.
• Use soft brushes on the mask for smooth fades; hard brushes for crisp cutouts.

Selection-to-mask workflow: Make a selection first, then fill the mask inside the selection (white) and outside (black), or invert as needed. This gives you a clean starting mask quickly.

Filter masks (non-destructive adjustments limited by a mask)

A filter mask applies an adjustment (like color correction) to a layer without permanently changing pixels. You can edit the filter settings later, and you can control where it applies using the mask.

How to add a filter mask for color adjustment

• Select the layer you want to adjust (often a merged character layer or a group).
• Add a Filter Mask.
• Choose a color adjustment filter (for example, hue/saturation or color balance).
• Edit the mask (paint black/white on the mask) to limit the adjustment to specific areas.

Practical example: Warm up only the character’s face and hands with a subtle hue shift, leaving clothing unchanged.

Practice sequence: isolate a character, refine edges, apply a masked adjustment

Goal

You will isolate a character silhouette from its background, clean the edges, then apply a color adjustment that affects only the character using a mask.

Step 1: Create an initial silhouette selection

• Zoom in enough to see the outline clearly.
• If the background is flat: use Contiguous Selection on the background, adjust threshold until it grabs most of it, then invert to select the character.
• If the background is complex: use Freehand/Lasso to trace the character silhouette. Don’t chase tiny details yet—aim for a clean, slightly simplified outline.
• Use Add mode to include missing parts (like hair tips) and Subtract mode to remove accidental background chunks.

Step 2: Refine the selection edges

• Inspect the boundary at high zoom.
• If the selection is too jagged: apply a small feather (or use a slight smoothing/refinement option if available in your selection tools).
• If you see a future “halo” risk: shrink the selection by a small amount (1–2 px depending on canvas size) before converting it into a mask.
• If you cut into the silhouette: undo the shrink or grow slightly, then subtract manually where needed.

Step 3: Convert the selection into a transparency mask

• Select the character’s paint layer (or the group containing the character).
• Add a Transparency Mask.
• With the selection active, fill the mask so the character is revealed and the background is hidden (white on character area, black outside).
• Deselect to avoid accidental partial edits.

Step 4: Edge touch-ups on the mask (non-destructive cleanup)

• Click the mask thumbnail to ensure you are painting on the mask, not the artwork.
• Use a hard brush to fix crisp edges (line-art/cel style).
• Use a soft brush at low opacity to gently blend hair edges or soft fabric.
• Toggle mask visibility (or temporarily disable it) to compare before/after and ensure you didn’t remove important silhouette parts.

Step 5: Apply a masked color adjustment with a filter mask

• Add a Filter Mask above the character layer/group.
• Choose a color adjustment (e.g., hue/saturation) and make a subtle change (small hue shift or slight saturation increase).
• Paint on the filter mask: black where you do not want the adjustment (for example, keep eyes or metal accessories unchanged), white where you want it fully applied.
• If the adjustment is too strong, reduce the filter strength rather than repainting the artwork.

Common pitfalls and how to fix them

Pitfall: jagged edges on the cutout

• Cause: rough lasso selection, low-resolution edge, or no refinement.
• Fix: refine the mask manually with a brush; apply a very small feather; consider shrinking the selection slightly before creating the mask to avoid background fringing.

Pitfall: visible halo/fringe from the background color

• Cause: selection includes edge pixels contaminated by the background.
• Fix: shrink selection 1–2 px before masking; paint black on the transparency mask along the edge; avoid excessive feathering that reveals the fringe.

Pitfall: forgetting to deselect

• Symptom: brush strokes, fills, or transforms affect only a small region unexpectedly.
• Fix: deselect immediately after converting a selection to a mask or finishing a localized edit; make it a habit to glance for the “marching ants” boundary before major actions.

Pitfall: editing the wrong layer or painting on the artwork instead of the mask

• Symptom: you permanently paint over details, or the mask doesn’t change when you paint.
• Fix: confirm the active thumbnail (layer vs. mask) before painting; if you made a mistake, undo and redo on the correct target. When in doubt, temporarily paint a small black/white stroke and see whether it hides/reveals (mask) or changes color (artwork).

Pitfall: transforming only part of a layer by accident

• Cause: an old selection is still active.
• Fix: deselect before transforming the whole layer; if you intended a partial transform, keep the selection but ensure it cleanly encloses the region to avoid seams.

Quick self-check checklist before you edit