drwaImage with scale or crop render very blur when export pdf file

Description

const exportPdf = async () => {
  const { createCanvas, loadImage } = require('canvas');
  const fs = require('fs');
  const path = require('path')
  let canvasWidth = 200;
  let canvasHeight = 200;
  const canvas = createCanvas(canvasWidth, canvasHeight, 'pdf');
  const ctx = canvas.getContext('2d');
  // image is a 800 x 800 px png 
  const imgUrl = "http://capcium.com/wp-content/themes/capcium/dist/images/-placeholders/img-example-square.png" 
  let img = await loadImage(imgUrl);
  const padding = 100;

  ctx.scale(0.1, 0.1)
  // draw origin image
  ctx.drawImage(img, padding, padding);
  // draw image with scale
  ctx.drawImage(img, img.width + padding * 2, padding, img.width - 1, img.height - 1);
  // draw image with crop
  ctx.drawImage(img, 0, 0, img.width - 1, img.height - 1, padding, img.height + padding * 2, img.width, img.height);
  
  const outPath = path.join(__dirname, `./output_${+new Date()}.pdf`)
  canvas.createPDFStream().pipe(fs.createWriteStream(outPath));
  console.log('end')
}

exportPdf()

Contributor guide

Tech stack

javascriptnodejs

Domain

backendperformance

Issue type

bug

DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.

3

Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.

1-3 hours

Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.

stale

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

clear

Prerequisites

basic JavaScriptNode.js canvas basics

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

50

Research direction

Investigate the canvas drawImage implementation in node canvas, specifically the PDF backend (Cairo). The issue likely lies in how scale and crop parameters are handled when writing to a PDF surface. Check the source files Canvas.cc and CanvasRenderingContext2D.cc for drawImage logic, and review any existing PDF related tests or comments. The 4 comments on the issue may contain further hints about the cause.