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# Demo crop comparison — `vcspull sync`

Dead-space crop approaches applied to `vcspull-sync.gif`
(**original 1175×202, 76K**). The static empty area is mostly *horizontal*
— the text fills only ~354px of the 1175px terminal width — plus ~49px of
vertical slack. Generated by a `/spike:bakeoff`.

## Original — 1175×202 · 76K

```{image} _static/demos/crop-comparison/sync-original.gif
:alt: original sync demo with dead space
```

## A · ffmpeg `cropdetect` (black mode) — ❌ no crop

**1174×202 · 68K.** The terminal background (`#282A36` Dracula, luminance
~43) sits *above* cropdetect's black threshold (24), so the whole frame
reads as content and only 1px is shaved. Raising `limit` past the bg
luminance returned no stable box.

```{image} _static/demos/crop-comparison/sync-cropdetect-black.gif
:alt: cropdetect black mode result (essentially uncropped)
```

## B · ImageMagick `-layers TrimBounds` — ❌ no crop + 5× bloat

**1175×202 · 360K.** `TrimBounds` trims *layer canvas bounds*, but agg
renders each frame full-size, so the union of bounds is the full frame.
Coalescing also unoptimised the file to 360K.

## C · ffmpeg `cropdetect=mode=mvedges` — ❌ no motion vectors

GIF frames are intra-coded; re-encoding to H.264 yielded no usable motion
vectors, so the motion-based detector had nothing to work from.

## D · ImageMagick union-trim (full crop) — ✅ 375×173 · 72K

`-coalesce` → clone/flatten → `-fuzz 4% -trim` → viewport crop → give 10px
of the terminal's **own** background on all sides → `-layers Optimize`. The
padding colour is sampled from the gif (`#282A36`, Dracula — *not*
Catppuccin), so it's seamless: the corner pixel is bit-identical to the
terminal bg, extending the terminal's margin rather than framing it.

```{image} _static/demos/crop-comparison/sync-imtrim-opt.gif
:alt: ImageMagick union-trim, cropped to content with margin
```

## E · Vertical-only crop (keep terminal width) — ✅ 1175×181 · 68K

`ffmpeg crop=1175:181:0:1` — trims only the vertical slack, preserving the
full terminal width so it still reads as a terminal.

```{image} _static/demos/crop-comparison/sync-vcrop.gif
:alt: vertical-only crop keeping full terminal width
```

## Verdict

| # | approach | result | dead space removed | verdict |
|---|----------|--------|--------------------|---------|
| A | ffmpeg cropdetect (black) | 1174×202 | ~0% | ❌ bg above threshold |
| B | ImageMagick TrimBounds | 1175×202, 360K | 0% | ❌ + bloat |
| C | ffmpeg cropdetect mvedges | — | — | ❌ no motion vectors |
| D | ImageMagick union-trim | 375×173 | ~69% | ✅ recommended |
| E | vertical-only ffmpeg crop | 1175×181 | ~10% (vertical) | ✅ keeps terminal look |

The only reliable spatial cropper for a terminal GIF is the **ImageMagick
union-trim recipe** (D) — `cropdetect`/`TrimBounds`/`mvedges` all failed on
non-black, full-frame content. Choose **D** for a compact demo or **E** to
keep the terminal framing; either way, re-render from the source at the
right size is cheaper still.