# Document benchmark on a public file

Feather 2.2 on a real presentation, so anyone can repeat it.

| File | Source | Licence | Size | SHA-256 |
|---|---|---|---:|---|
| `nasa-roman-expanding-our-view.pptx` | https://svs.gsfc.nasa.gov/vis/a010000/a014100/a014175/roman-expanding-our-view-presentation.pptx (page: https://svs.gsfc.nasa.gov/14175) | NASA/STScI, credit "STScI" | 79,897,270 bytes | `395a1e06c53fd45fd575a5150611141eca20c2bfceccdbd23ea3ebdbecb19775` |

31 slides; 36 raster images in `ppt/media` (8 JPEG, 15 JPG, 11 PNG, 2 TIFF) and 3 EMF.

## Method
- Feather: `feather-dev shrink` (Lossy, the app's defaults), engine as in Feather 2.2 (Build 806); the app gives the same file. The result opens as a valid zip.
- Quality: every JPEG and PNG in `ppt/media` before and after; the original is scaled to the size Feather placed the image at
  (ImageMagick) and both are scored with `ssimulacra2` (transparency on white).

## Result (2026-09-30)
| | Before | After |
|---|---:|---:|
| the file | 79.90 MB | 54.24 MB (−32 %) |
| 34 JPEG and PNG images | 32.2 MB | 6.5 MB (−80 %), mean score 75.3, median 75.1 |
| 2 TIFF (23.9 + 6.2 MB) and 1 EMF (16.1 MB) | 46.3 MB | 46.3 MB (left as they are) |

Feather also removed author, dates, software and the thumbnail. Two photos saved as PNG became JPEG.

## Limits
- Only JPEG and PNG inside documents are re-encoded; TIFF and EMF are kept, which is why this file is only 32 % smaller. Converting the two TIFFs would save
  roughly another 25 MB.
- One presentation. Word, Excel, Keynote, Pages and Numbers have no public benchmark file here yet.
- The quality score compares each image after scaling the original with ImageMagick, so part of the difference is the resampler.