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

### `drwaImage` with scale or crop render very blur.
[Here is result PDF](https://github.com/Saberjsd/assets/raw/main/comments/canvas/output_1622709280832.pdf)
#### This is preview with 200%:


### I wite a demo for show my problem for export PDF.

```js
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()
```