Upscaling with nearest neighbor produces blurry image rather than scaled pixels

clubside commented 3 weeks ago

Possible bug

Is this a possible bug in a feature of sharp, unrelated to installation?

[x] Running npm install sharp completes without error.
[x] Running node -e "require('sharp')" completes without error.

If you cannot confirm both of these, please open an installation issue instead.

Are you using the latest version of sharp?

[x] I am using the latest version of sharp as reported by npm view sharp dist-tags.latest.

What is the output of running `npx envinfo --binaries --system --npmPackages=sharp --npmGlobalPackages=sharp`?

  System:
    OS: Windows 10 10.0.19045
    CPU: (8) x64 Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz
    Memory: 15.48 GB / 31.85 GB
  Binaries:
    Node: 22.3.0 - G:\nodejs\node.EXE
    Yarn: 1.22.22 - G:\nodejs\yarn.CMD
    npm: 10.8.1 - G:\nodejs\npm.CMD
    pnpm: 9.5.0 - G:\nodejs\pnpm.CMD
  npmPackages:
    sharp: ^0.33.4 => 0.33.4

Does this problem relate to file caching?

The default behaviour of libvips is to cache input files, which can lead to EBUSY or EPERM errors on Windows. Use sharp.cache(false) to switch this feature off.

[x] Adding sharp.cache(false) does not fix this problem.

Does this problem relate to images appearing to have been rotated by 90 degrees?

Images that contain EXIF Orientation metadata are not auto-oriented. By default, EXIF metadata is removed.

To auto-orient pixel values use the parameter-less rotate() operation.
To retain EXIF Orientation use keepExif().
[x] Using rotate() or keepExif() does not fix this problem.

What are the steps to reproduce?

const avatar = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAgAAAAICAIAAABLbSncAAAAAXNSR0IArs4c6QAAAA5lWElmTU0AKgAAAAgAAAAAAAAA0lOTAAAATklEQVQIHWN00ZdlwAaYsAmCxHBKsAAlq3wd0fS1bd7PBBS1qp+78HoORA7IAHKBgkxyihJAoeOX44AMIAIygFwgg/HO3DI0cyBcnJYDAE6jE2C2ld0zAAAAAElFTkSuQmCC'
const dataUri = avatar.match(/^data:.+\/(.+);base64,(.*)$/)
const dataBuffer = Buffer.from(dataUri[2], 'base64')
const avatarSharp = sharp(dataBuffer)
avatarSharp.resize(256, { kernel: sharp.kernel.nearest })
avatarSharp.extract({ left: 0, top: 0, width: 256, height: 256 })
avatarSharp.png()
await avatarSharp.toFile('avatar.png')

What is the expected behaviour?

That each pixel is just scaled with no interpolation, especially in this case where 8x8 to 256x256 is proportional.

Please provide a minimal, standalone code sample, without other dependencies, that demonstrates this problem

The code is above.

Please provide sample image(s) that help explain this problem

Here is the source image: Original Image Here is the sharp upscale with nearest neighbor: Here is the Photoshop upscale with nearest neighbor:

clubside commented 3 weeks ago

Not providing a height was causing an error I didn't spot. If I force 256x256 using avatarSharp.resize(256, 256, { kernel: sharp.kernel.nearest }) everything works great. How do I set the options to proportional height while still passing the kernel option?

clubside commented 3 weeks ago

Sorry, I see in the docs I can set the height to null which solves everything. Sorry for the trouble and thanks again for a wonderful library!

lovell commented 3 weeks ago

Alternatively, perhaps move the width into the options to make it less ambiguous:

- avatarSharp.resize(256, { kernel: sharp.kernel.nearest })
+ avatarSharp.resize({ width: 256, kernel: sharp.kernel.nearest })

lovell / sharp