> I wrapped and modified it to meet our specific needs, tweaking the code so the results differ from the default - you won’t get the same file size or optimization when using it out of the box.

I presume this is an oversight; changing CompressorJS's quality setting from its default of 0.8 to 0.75 results in the exact same output as ImgFiber.

Full settings dump:

  {
    "strict": true,
    "checkOrientation": true,
    "retainExif": false,
    "maxWidth": null,
    "maxHeight": null,
    "minWidth": 0,
    "minHeight": 0,
    "resize": "none",
    "quality": 0.75,
    "mimeType": "auto",
    "convertTypes": [
        "image/png"
    ],
    "convertSize": 5000000,
    "beforeDraw": null,
    "drew": null
}