CodeSampleX

Sample

sharp 0.35.3: extract a region of an image with sharp

Verified sample for npm sharp 0.35.3: extract a region of an image with sharp. The contract ran on node 22 · linux alpine/x64 · docker and passed.

sha256:85fd36ffecd67611eeba681381be936a32df20871d836f0497e81505bc34d64e

This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured. How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people. MIT-0

Execution evidence

The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.

Evidence basis
Signed contract pass
Verification receipts
1
Signing keys that built it
1
Declared environment linux 24 · ubuntu · glibc 2.39 x64 npm

Verification-run environments

Environment Contract Stages Run
node 22 · linux alpine/x64 · docker ed25519:2175b912ea1c23b1 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1		 2026-08-20

Case

HOW
Goal
extract a region of an image with sharp
Packages
Symbols
  • sharp.extract
Created
2026-08-20T03:52:32Z

Contract

  1. extracts a rectangular region from an image buffer using left, top, width, and height
  2. extracted image metadata matches the specified region dimensions

Files

  • PROMPT.md
  • csx.json
  • package-lock.json
  • package.json
  • spec.json
  • src/index.mjs
  • test/contract.mjs

Download the source artifact (tar.gz)

Source

PROMPT.md
Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: extract a region of an image with sharp
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/sharp@0.35.3
Demonstrate these symbols/APIs:
  - sharp.extract

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.
csx.json
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package-lock.json
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package.json
{
  "name": "sharp-extract-sample",
  "version": "1.0.0",
  "type": "module",
  "description": "Extract a region of an image with sharp",
  "main": "src/index.mjs",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "sharp": "0.35.3"
  }
}
spec.json
{
  "schemaVersion": 1,
  "goal": "extract a region of an image with sharp",
  "kind": "HOW",
  "packages": [
    "pkg:npm/sharp@0.35.3"
  ],
  "symbols": [
    "sharp.extract"
  ]
}
src/index.mjs
import sharp from 'sharp';

/**
 * Extracts a rectangular region from an input image buffer.
 * @param {Buffer|Uint8Array} inputBuffer - The image data buffer.
 * @param {Object} options - The region options.
 * @param {number} options.left - Zero-indexed offset from left edge.
 * @param {number} options.top - Zero-indexed offset from top edge.
 * @param {number} options.width - Width of region to extract in pixels.
 * @param {number} options.height - Height of region to extract in pixels.
 * @returns {Promise<Buffer>} - The extracted image region buffer.
 */
export async function extractRegion(inputBuffer, options) {
  const { left, top, width, height } = options;
  return await sharp(inputBuffer)
    .extract({ left, top, width, height })
    .toBuffer();
}
test/contract.mjs
import assert from 'node:assert/strict';
import sharp from 'sharp';
import { extractRegion } from '../src/index.mjs';

async function testContract() {
  // Create a 200x100 blank PNG image buffer offline
  const inputBuffer = await sharp({
    create: {
      width: 200,
      height: 100,
      channels: 4,
      background: { r: 10, g: 20, b: 30, alpha: 1 }
    }
  }).png().toBuffer();

  // Verify original input image dimensions
  const inputMeta = await sharp(inputBuffer).metadata();
  assert.equal(inputMeta.width, 200, 'input width should be 200');
  assert.equal(inputMeta.height, 100, 'input height should be 100');

  // Extract a 50x30 region at left=20, top=10
  const regionOptions = { left: 20, top: 10, width: 50, height: 30 };
  const extractedBuffer = await extractRegion(inputBuffer, regionOptions);

  // Assert extracted image dimensions and properties
  const extractedMeta = await sharp(extractedBuffer).metadata();
  assert.equal(extractedMeta.width, 50, `expected width 50, got ${extractedMeta.width}`);
  assert.equal(extractedMeta.height, 30, `expected height 30, got ${extractedMeta.height}`);
  assert.equal(extractedMeta.format, 'png', 'expected format to be png');

  console.log('Contract test passed: sharp image region extraction verified');
}

testContract().catch((err) => {
  console.error('Contract test failed:', err);
  process.exit(1);
});

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