Digital Drawing on a Tablet: Selections for Fast Edits and Perfect Edges

Selections: the fastest way to edit without damaging edges

A selection is a temporary “mask” that tells your tablet app where edits are allowed. Anything you paint, erase, move, transform, or fill will only affect the selected area (or everything outside it, if you invert). Think of selections as a precision tool: instead of trying to repaint perfectly up to a line, you define the boundary once and then work freely inside it.

Selections are especially powerful for: (1) making fast edits to parts of a sketch, (2) fixing edge problems like tangents and bumps, (3) repainting a region without touching surrounding work, and (4) filling flat colors with zero spill.

Selection anatomy: boundary, edge quality, and active operations

• Boundary: the shape of the selected area (lasso, rectangle, ellipse, or color-based).
• Edge quality: controlled by anti-aliasing and feathering. This determines whether the edge is crisp, slightly blended, or very soft.
• Operations: add to selection, subtract from selection, intersect, invert, and clear/deselect.

Selection methods you’ll use constantly

1) Freehand / Lasso selection (best for organic shapes)

Use lasso when you need to isolate an irregular shape: a hand, a strand of hair, a fold, or a chunk of a sketch you want to nudge.

• Tip: zoom in and draw the lasso slightly outside the edge you want to preserve, then refine with subtract.
• Tip: if your app supports it, use a polyline lasso (tap-to-place points) for straight-edged objects.

2) Rectangle / Ellipse selection (best for clean geometric edits)

Use rectangle/ellipse for quick, controlled edits: repositioning an eye, scaling a logo shape, straightening a horizon, or isolating an area for repaint.

• Tip: many apps allow holding a modifier to constrain proportions (perfect square/circle) or to draw from center.

3) Color-based selection (magic wand / select similar)

Color-based selection targets pixels by value and/or hue. It’s ideal when you already have flat colors or clear value blocks and want to select them instantly.

Continue in our app.

• Listen to the audio with the screen off.
• Earn a certificate upon completion.
• Over 5000 courses for you to explore!

Or continue reading below...

Download the app

• Tolerance controls how wide the selection range is. Low tolerance selects only very similar pixels; high tolerance grabs more variation (including anti-aliased edge pixels).
• Contiguous (if available) limits selection to touching pixels; turning it off selects that color everywhere on the layer.

Common use: selecting a flat silhouette to repaint inside it, or selecting a background value to adjust without affecting the subject.

Add, subtract, invert: building perfect selections

Most selection work is not “one perfect lasso.” You build it in parts.

• Add to selection: expand the selected area by drawing more selection shapes.
• Subtract from selection: carve away mistakes (great for cutting around fingers, spikes, or small gaps).
• Intersect: keep only the overlap between two selections (useful for trimming a lasso to a rectangle boundary).
• Invert: swap selected/unselected areas. This is the fastest way to protect a subject while editing the background, or vice versa.

Mini workflow: lasso + subtract for clean boundaries

1. Make a rough lasso around the area you want.
2. Switch to Subtract.
3. Zoom in and subtract small “bites” to refine the edge.
4. If you remove too much, switch to Add and restore.

Feathering vs anti-aliasing: controlling edge softness

Two settings determine whether your selection edge is crisp or soft. They sound similar but behave differently.

Anti-aliasing (edge smoothing)

Anti-aliasing creates a thin band of partially selected pixels along the edge so curves look smooth instead of jagged. It’s usually desirable for painted artwork and curved silhouettes.

• When to keep it ON: most painting, curved shapes, character silhouettes, soft shading transitions.
• When to turn it OFF: pixel-art style, hard-edged graphic shapes, or when you need a perfectly crisp boundary for a flat fill with no semi-transparent edge.

Feathering (edge blur radius)

Feathering intentionally softens the selection by expanding the edge into a gradient over a chosen radius. This is great for soft light, atmospheric blends, and subtle adjustments—but it can ruin “perfect edges” if used accidentally.

• When to use feathering: gentle value shifts, soft shadows, glow adjustments, vignette-like edits.
• When to avoid feathering: filling flats, crisp silhouettes, graphic line art boundaries, hard cutouts.

Visual examples: what “too soft” looks like

Practical uses (with step-by-step)

1) Move/transform part of a sketch without redrawing

Use this when proportions are close but one part needs repositioning (e.g., shifting an eye, rotating a hand, enlarging a prop).

1. Select the area with Lasso (include a small buffer around it).
2. Use Transform (move/scale/rotate). Keep an eye on the edge: scaling up can reveal softness or blur.
3. If your app offers it, choose a transform resampling mode that preserves sharpness for line work.
4. Deselect and inspect the seam. If there’s a gap, use a small selection to patch and repaint only the seam area.

Tip: if the moved part leaves a “hole,” invert the selection (select the hole area) and repaint/clone only the background region.

2) Cleaning tangents and awkward edge kisses

Tangents happen when two shapes barely touch, creating confusing merges (e.g., a finger edge kissing the jawline, hair touching the shoulder outline). Selections let you separate forms cleanly.

1. Zoom in on the tangent area.
2. Lasso-select one of the forms (the one you want to move or reshape).
3. Transform slightly (nudge a few pixels) to create clear separation.
4. If you need a micro-reshape instead of a move: keep the selection active and repaint/erase inside it to adjust the contour without affecting the other form.

Checkpoint: after fixing, squint/zoom out. The forms should read as clearly separate shapes.

3) Isolate a region for repainting (no collateral damage)

This is the “surgical repaint” workflow: you can repaint a cheek, a sleeve, or a background patch without touching nearby edges.

1. Create a selection around the region (lasso or rectangle).
2. Set Feather = 0 for hard boundaries, or a small feather for subtle blending (use intentionally).
3. Paint, adjust, or erase freely—your strokes cannot cross the selection boundary.
4. Deselect and check for edge artifacts. If you see a halo, you likely used feathering or selected with too much tolerance.

4) Fill flat colors without spill (perfect edges)

Selections are the most reliable way to get clean flats, especially when line edges are complex.

1. Make a selection of the shape you want to fill (lasso, or color-select an existing silhouette).
2. Ensure Feather = 0.
3. Choose whether you want Anti-alias ON (smooth edge) or OFF (crisp graphic edge).
4. Use Fill (or paint with a large brush) inside the selection.
5. If tiny unfilled gaps remain (common with complex edges), expand the selection slightly (if your app has “expand/grow selection”) and refill.

Tip: if your app has “expand/contract selection,” use it instead of feathering when you want to push an edge outward/inward while keeping it hard.

Skill drill: silhouette → repaint inside with multiple colors (outer edge stays perfect)

This drill trains the core habit: define a clean boundary once, then paint freely inside it. You’ll end with a crisp silhouette edge even after multiple color passes.

Part A: Create a flat-color silhouette

1. Draw a simple subject silhouette (choose something readable: a leaf, a bottle, a cat head, a boot).
2. Make a selection around the silhouette using Lasso (take your time on the outer contour).
3. Set Feather = 0. Turn Anti-alias ON for a smooth curve (or OFF if you want a graphic cutout style).
4. Fill the selection with a single mid-tone color (this is your silhouette base).
5. Deselect and zoom in: the outer edge should look clean and intentional.

Part B: Lock the outer edge using selection (not careful brushing)

1. Use Color-based selection on the silhouette color to select the entire silhouette. Adjust tolerance so it selects the silhouette cleanly without grabbing the background.
2. If your app offers it, enable Contiguous so only the silhouette region is selected.
3. With the silhouette selected, you can now paint multiple colors inside it. The outer edge cannot be damaged because the selection boundary is protecting it.

Part C: Repaint inside with multiple colors (3-pass exercise)

1. Pass 1 (big shapes): paint 2–3 large color regions inside the silhouette (e.g., top light area, mid area, bottom shadow area). Use a big brush; don’t worry about staying inside—selection handles that.
2. Pass 2 (secondary shapes): add smaller accents (spots, stripes, label shapes, veins). Use rectangle/ellipse selections for geometric accents, lasso for organic ones. Practice Add/Subtract to build clean internal shapes.
3. Pass 3 (edge stress test): paint right up against the silhouette boundary with a textured brush. Because the selection is active, the outer edge should remain perfectly clean.

Troubleshooting checklist (if the edge isn’t perfect)

• Fuzzy halo: feathering was above 0, or you selected with too high tolerance and included semi-transparent edge pixels. Redo selection with feather 0 and lower tolerance.
• Jagged edge: anti-alias was off (or canvas resolution is too low). Turn anti-alias on for the selection/fill, or work at higher resolution.
• Color spill outside: you painted without an active selection, or you deselected mid-way. Re-select the silhouette (color-based selection) before continuing.

Optional challenge: invert and repaint the background edge

Keep the silhouette selection active, then use Invert to select everything except the silhouette. Paint a background gradient or texture. This trains you to protect the subject edge while freely editing the surroundings.