Source: https://guthlabs.ai/docs/instruments/aspect-ratio-crop-calculator/implementation/

instrument implementation / implementation-contract

# Aspect Ratio / Crop Calculator implementation

A source-bound implementation contract for Aspect Ratio / Crop Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t5-001

**Effect**: Computation or source lookup only

## Input and validation requirements

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.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "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."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/aspect-ratio-crop-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/aspect-ratio-crop-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/aspect-ratio-crop-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`