Source: https://guthlabs.ai/docs/instruments/aspect-ratio-crop-calculator/
instrument / verified-clean
# Aspect Ratio / Crop Calculator
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Audio, Music, Photography & Color
**Tranche**: tranche-5
**Evidence ID**: t5-001
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The core uniform-fit formula is standard, but the specification needs explicit definitions for total versus per-side bar thickness, crop behavior, input units, integer rounding, and upscaling. It should either remove crop-pixels from the fit mode or add a separately documented crop-to-fill formula and mode.
### Formula and scope findings
- The scale formula is correct for uniformly fitting the entire source inside the target, assuming upscaling is allowed: scale=min(targetW/srcW,targetH/srcH).
- Bar-size calculation is underspecified: total leftover space is targetW-fittedW and targetH-fittedH, while per-side bar thickness is half of each leftover; the spec does not say which value is output.
- No crop formula is provided. A fit operation produces no crop pixels, so the claimed crop-pixels output is either always zero or requires a separate crop-to-fill mode and formula.
- Pixel rounding behavior is unspecified; fitted dimensions and per-side bars can be fractional even when all inputs are integer pixel dimensions.
- The spec does not state whether source and target dimensions must use the same units or whether aspect-ratio-only inputs are supported.
### Unit assumptions
- All source and target dimensions are positive pixel counts unless explicitly documented otherwise.
- sourceW, sourceH, targetW, and targetH must use the same linear unit; dimensions in pixels are assumed for the test vectors.
- Fitted dimensions are computed as real numbers before any optional integer-pixel rounding.
- Bar sizes below report both total leftover space and equal per-side thickness.
- Because this is fit-without-cropping, cropPixels is expected to be 0 in these vectors.
## Boundary hardening
**BREAK_CLAIMED** · SELF_FLAGGED
Zero source dimensions make the scale formula undefined, but a naive plain-JavaScript implementation could propagate Infinity or invalid fitted dimensions instead of rejecting the input. The specification does not state explicit validation behavior for zero or negative resolutions.
## Errata and corrections
No applied erratum is attached to this unique-name record.
## Inspectable example
4 review vectors are recorded. One source-bound sample is shown below.
````
{
"inputs": {
"sourceW": 1920,
"sourceH": 1080,
"targetW": 1920,
"targetH": 1080,
"units": "pixels"
},
"expected_outputs": {
"scale": 1,
"fittedWidth": 1920,
"fittedHeight": 1080,
"barLeft": 0,
"barRight": 0,
"barTop": 0,
"barBottom": 0,
"cropPixels": 0
},
"working": "scale=min(1920/1920,1080/1080)=min(1,1)=1. fittedWidth=1920*1=1920. fittedHeight=1080*1=1080. leftoverWidth=1920-1920=0, so left/right bars=0/2=0 each. leftoverHeight=1080-1080=0, so top/bottom bars=0/2=0 each. No cropping occurs, so cropPixels=0."
}
````
## Related workflows
No source-defined multi-instrument workflow membership is recorded.
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`
- `evidence-tranche5/tranche5-results.json`
- `BOUNDARY_HAZARD_CATALOG.json`