usefulweb.appDependable little tools for people and AI agents. Flipline

Drawing, pixel art & animation

Flipline

A few drawings. A little life. Make a flipbook in your browser.

Flipline is a free drawing, pixel-art and animation studio that runs on your device. Sketch poses across layers, compare onion skins and play drawings with adjustable holds. Pixel Studio adds indexed sprite drawing, palettes and live loops; Retro Lab converts photos with color development, dithering and shared batch recipes. Export GIFs, PNG sequences or sprite atlases, and keep editable project files for your next idea.

Launch Flipline → Tutorials

Free · runs in your browser · no sign-up · Version 1.2.0

Flipline drawing board showing a bouncing ball with onion skins, drawing tools, layers and a twelve-drawing timeline

Screenshots

Features

  • Start with a mark

    Draw with a pencil or eraser, add lines, rectangles and ellipses, and choose ink, stroke width and shape fill.

  • A timeline you can feel

    Add blank drawings, duplicate poses, reorder them and hold each drawing for 1–10 timeline ticks.

  • See the pose before

    Previous and next drawings appear as red and blue onion skins with adjustable opacity.

  • Give your scene layers

    Up to four layers keep the stage and action separate. Rename, reorder, hide, lock and change opacity.

  • Adjust every mark

    Select and move individual strokes, shapes or images. Copy, paste, duplicate, delete and nudge with the keyboard.

  • Find the right rhythm

    Play at 1–30 FPS, loop a motion study or inspect drawings one at a time. Timing uses drawing holds.

  • Bring a sequence

    Import PNG, JPEG or WebP images as new drawings. Move and scale them with the canvas in an editable project.

  • Let it move elsewhere

    Export animated GIFs, transparent PNG sequences with timing JSON, or sprite sheets with atlas coordinates.

  • Keep the editable idea

    Local browser autosave, eight recent projects and .flipline.json downloads preserve drawings and settings.

  • Small pixels, big ideas

    Open Pixel Studio for crisp pencils, erasers, lines, rectangles and connected bucket fill on an indexed canvas.

  • A palette that travels

    Choose up to 32 colors, remap every cel, mirror your brush, flip or shift pixels, and rotate the canvas without smoothing.

  • A loop while you draw

    Live sprite preview plays while you edit. Duplicate frames, set holds and layers, import uniform sprite sheets and export exact palette GIFs.

  • Keep the pixel original

    Pixel sprites have their own browser autosave, recent projects, undo and editable .flipline-pixels.json files. PNG and sprite atlases retain transparency.

  • Give images another era

    Retro Lab combines authored palettes, RGB adjustments, gamma and saturation with ordered or error-diffusion dithering. Compare the source with the exact pixel result.

  • A collection, one color language

    Apply a shared palette and recipe to eight images. Export PNGs and editable pixel projects together; import and export HEX, GPL and JASC-PAL palettes.

  • Useful beyond the studio

    Exposure sheets, sprite layout planning and editable motion study generation are available through HTML, API and MCP.

Templates

Start from a ready-made project and change it to fit.

For AI agents

Flipline runs on a deterministic engine. The same functions are available as tools with a JSON API and MCP, so scripts and AI agents get exactly the results the app shows.

  • Animation Exposure Sheet – Turn drawing holds into a precise animation timing sheet.
    Tool page · POST https://flipline.usefulweb.app/api/v1/tools/flipline-exposure-sheet/calculate · MCP flipline_exposure_sheet
  • Sprite Sheet Layout Planner – Plan an animation atlas with exact frame rectangles and padding.
    Tool page · POST https://flipline.usefulweb.app/api/v1/tools/flipline-sprite-sheet/calculate · MCP flipline_sprite_sheet
  • Animation Motion Study Generator – Generate an editable flipbook to compare animation easing curves.
    Tool page · POST https://flipline.usefulweb.app/api/v1/tools/flipline-motion-study/calculate · MCP flipline_motion_study
  • Pixel Art Image Converter – Convert images into pixel art with palettes, dithering and retro effects.
    Tool page · POST https://flipline.usefulweb.app/api/v1/tools/flipline-pixel-quantizer/calculate · MCP flipline_pixel_quantizer
  • Pixel Grid Transform – Flip, rotate or shift an indexed pixel sprite without blur.
    Tool page · POST https://flipline.usefulweb.app/api/v1/tools/flipline-pixel-transform/calculate · MCP flipline_pixel_transform
  • Pixel Palette Format Converter – Convert HEX, GIMP GPL and JASC-PAL palettes without changing color order.
    Tool page · POST https://flipline.usefulweb.app/api/v1/tools/flipline-palette-converter/calculate · MCP flipline_palette_converter
  • Retro Pixel Art Batch Processor – Apply one retro palette and effect recipe to a ZIP of images.
    Tool page · POST https://flipline.usefulweb.app/api/v1/tools/flipline-retro-batch/calculate · MCP flipline_retro_batch

Build a project through the API, then open it in the app with a link to https://flipline.usefulweb.app/app#project=<base64url JSON>.

Import & export

Import

  • Flipline project (.flipline.json)
  • PNG
  • JPEG
  • WebP
  • Uniform PNG/JPEG/WebP sprite sheets
  • Pixel sprite (.flipline-pixels.json)
  • Retro recipe (.flipline-retro.json)
  • HEX, GIMP GPL or JASC-PAL text palette

Export

  • Retro recipe (.flipline-retro.json)
  • HEX, GPL and JASC-PAL palettes
  • Retro PNG and editable asset batch ZIP
  • Pixel sprite (.flipline-pixels.json)
  • Flipline project (.flipline.json)
  • Animated GIF
  • PNG sequence + timing JSON (ZIP)
  • Sprite sheet + atlas JSON (ZIP)
  • Current drawing PNG
  • SVG with embedded PNG
  • Print / PDF via browser

Keyboard shortcuts

Keyboard shortcuts in Flipline
KeysAction
B / E / VPencil / Eraser / Select
SpacePlay / pause
Ctrl + SSave editable project
Ctrl + OOpen editable project
Ctrl + Z / Ctrl + Shift + ZUndo / redo
Ctrl + C / Ctrl + V / Ctrl + DCopy / paste / duplicate selected mark
DeleteDelete selected mark
Arrow keysNudge selected mark or switch drawing
F / G / ?Fit / Grid / Help

Frequently asked questions

What does a retro recipe keep?

Retro Lab recipes save conversion settings and a resolved palette, without source images. Reimport photos after reopening. Settings autosave locally; batch ZIPs include PNGs, editable pixel projects, the shared recipe and a manifest. Use /static/apps/flipline/retro.schema.json for the format.

Which palette and dithering formats are supported?

Retro Lab uses up to 32 RGB colors, authored presets or imported HEX, GIMP GPL and JASC-PAL text palettes. Choose nearest matching, ordered Bayer 4 × 4 or serpentine Floyd–Steinberg with adjustable strength. Source alpha below the threshold becomes transparent; PNG scaling repeats pixels exactly.

How does Pixel Studio fit with the drawing board?

Pixel Studio is an independent pixel-art workflow inspired by Piskel. It keeps indexed pixels, layers, palettes and animation holds in .flipline-pixels.json files; /static/apps/flipline/pixels.schema.json documents the format. Open from the rail or the main Open button, or send rendered frames to the drawing board. It does not open .piskel files.

Does pixel GIF export preserve my colors?

Pixel Studio uses the project palette and transparent index zero. Fully opaque palette pixels keep their exact RGB values. Layer-opacity blends map back to the nearest palette color; alpha below 128 becomes transparent. PNG keeps full alpha. This differs from the drawing board GIF exporter, which uses RGB332 and paper color.

Do my drawings leave this device?

The workspace processes drawings and exports locally. Editable projects autosave in this browser, and you can download a file backup. Pixel Studio also runs locally. The separate Pixel Art Image Converter and Retro Pixel Art Batch Processor upload source files to the server. Palette, planning and grid tools use text or numeric inputs.

Is this Pencil2D in a browser?

Flipline is an independent app inspired by the frame-by-frame drawing, timeline and onion skin workflow. It does not reuse Pencil2D branding or code and cannot open Pencil2D PCL/PCLX projects.

What is a drawing hold?

A hold of 2 lasts two timeline ticks. At 12 FPS it lasts one sixth of a second. GIF durations round to 10 ms units; the exposure sheet reports both ideal and GIF timing.

Which exports preserve transparency?

Enable Transparent PNG background in Canvas settings for PNG sequences and sprite sheets. GIF output uses the paper color and a fixed 256-color palette. SVG export embeds the rendered PNG.

Can an agent create an editable project?

Yes. The motion study generator returns a Flipline project, and /project.schema.json documents the file format. Open it from a file or a #project= base64url JSON fragment.

Limitations

What Flipline does not do (yet):

  • Retro Lab: eight images, 4 MB and 2 MP per image, 8 MP decoded in total, 128 native pixels per side and 1–8 integer PNG scaling. Recipes contain settings only.
  • Retro conversion uses binary alpha, nearest RGB palette matching and manual controls. No video conversion, AI stylization, binary palette formats or PixaTool preset import.
  • Pixel Studio: 1–128 pixels per side, 24 frames, four layers, 32 palette colors and 524288 stored cel pixels. PNG/JPEG/WebP imports are limited to 4 MB and 2 MP; editable pixel files to 4 MB. Pixel Studio edits indexed pixels; Retro Lab adds dithering before import.
  • Pixel GIFs use binary transparency and at most 12 million total frame pixels. No animated GIF import, .piskel import, arbitrary selections or tile-map editing.
  • Up to 24 drawings, four layers, 2 MP per canvas and 1600 px per side. Holds are 1–10 ticks at 1–30 FPS.
  • Project limits: 50000 points, 2000 marks and approximately 6 MB of embedded image data. Imports are limited to 16 MB project files or 3 MB per image.
  • Drawing board GIF exports use a fixed RGB332 palette, no transparency, at most 12 million total frame pixels and 10 ms timing units.
  • No audio timeline, camera animation, pressure-sensitive brushes, automatic arbitrary-artwork inbetweening or video export.
  • Images can be moved as marks; there are no free-transform handles. Canvas resizing scales all normalized drawing positions.
  • Browser storage can be cleared or evicted. Download an editable project as a durable backup.

Tutorials

Learn Flipline step by step.

  1. Your first little animationDraw a pose, duplicate it and bring it to life.Beginner 5 min
  2. Layers, image sequences and useful exportsOrganize drawings and export animation files for the web or a game.Intermediate 6 min
  3. Make a pixel sprite and a little loopDraw crisp pixels, work with a palette, import sprite sheets and export a transparent animation.Beginner 7 min
  4. Turn a photo into a retro pixel imageMake a limited-color image, compare dithering styles and keep a consistent palette across a batch.Beginner 7 min

Ready to try it?

Launch Flipline →

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