154 lines
6.5 KiB
Markdown
154 lines
6.5 KiB
Markdown
# Repixelizer
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Repixelizer is a standalone Python CLI for images that are doing a pixel art impression instead of actually respecting the grid.
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It is aimed at the annoying middle ground: sprites, emblems, and logos that look locally pixelated but fall apart the second you ask them to commit to one lattice like grown-ups.
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Instead of pretending this is a resize problem, Repixelizer treats it as lattice inference plus local structure preservation: infer the implied grid, choose real output cells, and snap them back onto a coherent pixel lattice while preserving the source's local adjacency patterns.
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## Examples
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Repixelizer was built to rescue fake pixel art, but it can also be used to generate pixel art directly from non-pixel source art when the shapes are clean and the local structure is doing something useful.
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Rows show the source art, a plain Lanczos downscale to the same target size, and the repixelized result. The bottom row also carries a sword-guard picture-in-picture, because that tiny region is one of the more honest tests of whether the tool is preserving local cell adjacency instead of just getting the vibes approximately correct.
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That is the two-headed pitch in one image: force non-pixel art onto a coherent grid, or take AI pixel art that only respects the grid locally and make it commit.
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## Current Status
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This is already a serious experimental baseline, not a toy prototype:
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- CUDA-backed inference and solver paths are wired up
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- round-trip corpus benchmarking is built in
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- soft and crisp corruption profiles are supported
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- diagnostics and baseline comparisons are written automatically
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- a black-box tuning harness exists for longer offline parameter sweeps
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The current pipeline is especially strong on benchmarked sprite and emblem inputs where local fake-pixel texture is meaningful but the global grid is inconsistent.
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## Quickstart
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```powershell
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python -m venv .venv
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.venv\Scripts\python -m pip install -e .[dev]
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```
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Run the optimizer:
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```powershell
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repixelize input.png --out output.png
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repixelize input.png --out output.png --diagnostics-dir diagnostics --device auto
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```
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Run the optimizer plus baselines:
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```powershell
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repixelize compare input.png --out output.png --diagnostics-dir diagnostics
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```
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## Corpus And Benchmarks
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Prepare a local Creative Commons corpus:
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```powershell
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repixelize prepare-corpus --corpus-dir examples/corpus
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```
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Run the round-trip benchmark:
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```powershell
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repixelize benchmark --corpus-dir examples/corpus --out-dir artifacts/benchmark
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```
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Useful benchmark flags:
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- `--profile soft` or `--profile crisp`
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- `--case <name>` repeated for a focused slice
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- `--limit <n>` for the first `n` matching cases
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- `--infer-size` to test automatic size inference
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- `--keep-existing` if you explicitly want to preserve an old output directory
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By default the benchmark clears its output directory before each run so the artifacts folder stays readable.
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## Tuning
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Repixelizer includes a black-box tuning loop for longer offline searches over solver weights:
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```powershell
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repixelize tune --corpus-dir examples/corpus --out-dir artifacts/tuning --profile soft --limit 8
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```
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This is intentionally a search-based tuner, not gradient descent. The objective depends on discrete argmins, thresholding, and benchmark comparisons, so it is better treated as a repeatable black-box optimization problem.
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## Repository Hygiene
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This repo is set up to be safe for local experimentation:
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- generated outputs under `artifacts/` are ignored
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- local corpus payloads under `examples/corpus/originals/` are ignored
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- archived raw sprite sheets under `examples/corpus/source-sheets/` are ignored
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- generated corpus metadata files are ignored
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That keeps benchmark assets, attribution exports, and tuning runs from polluting upstream history while still keeping the code, docs, and corpus layout tracked.
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## Repo Layout
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- `src/repixelizer`: core package
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- `tests`: focused regression tests
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- `docs/spec.md`: product and technical spec
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- `docs/implementation-plan.md`: working roadmap
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- `examples/corpus/README.md`: local corpus layout and attribution workflow
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Core modules:
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- `inference.py`: target size and phase inference
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- `continuous.py`: source-aware lattice snapping and local discrete refinement
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- `metrics.py`: fidelity, adjacency, and motif metrics
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- `benchmark.py`: corpus benchmark runner
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- `tuning.py`: black-box hyperparameter search harness
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- `synthetic.py`: facsimile generation for tests and benchmarks
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## Validation
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Run the focused test suite with:
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```powershell
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.venv\Scripts\python -m pytest -q
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```
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## Regenerating README Assets
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The README comparison sheet is generated from repo-tracked fixtures, not from random artifacts left lying around:
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```powershell
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.venv\Scripts\python scripts\generate_readme_previews.py --vector-input tests\fixtures\real\ai-badge-vector.png --ai-input tests\fixtures\real\ai-badge-cleaned.png --out-sheet docs\readme-assets\badge-example-sheet.png --out-guard-crop docs\readme-assets\guard-right-crop-comparison.png --scratch-dir artifacts\readme-build --device cpu
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```
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That regenerates the README sheet, the standalone sword-guard closeup strip, and scratch outputs under `artifacts/readme-build/` so you can inspect the actual low-res results used to build the docs sample.
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## Diagnostic Closeups
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For docs or regression notes, you can generate reproducible source/output closeups from output-grid cell coordinates with:
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```powershell
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.venv\Scripts\python scripts\render_focus_crop.py --input tests\fixtures\real\ai-badge-cleaned.png --out docs\readme-assets\guard-right-crop-source-final.png --cell-bbox 73 20 107 44 --panels source,final --scale 16 --steps 48 --device cpu
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```
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If you want the full internal state sheet instead of the docs-facing comparison:
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```powershell
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.venv\Scripts\python scripts\render_focus_crop.py --input tests\fixtures\real\ai-badge-cleaned.png --out docs\readme-assets\guard-right-crop-states.png --cell-bbox 73 20 107 44 --panels source,snap,relaxed,final --scale 16 --steps 48 --device cpu
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```
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Notes:
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- `--cell-bbox` is in output-grid coordinates, not source-image pixels.
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- The script maps that region back to the matching source crop automatically.
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- `--device cpu` is the polite choice for docs generation if you do not want to stress the GPU for a tiny crop.
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## Notes
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- The local corpus is optional; the codebase is still usable without it.
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- The benchmark and tuning commands are designed for iterative local work, not for shipping generated artifacts in git.
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- Palette enforcement is optional and can be left off for unconstrained recovery runs.
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