blur -> threshold chaining doesn't work as expected

[thot-experiment]

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

What are the steps to reproduce?

When chaining .blur().threshold() the threshold step is not perfomed

What is the expected behaviour?

.threshold() should be performed

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

import sharp from 'sharp'
import fs from 'fs/promises'

let file = await fs.readFile('test.png')

let onepass = await sharp(file)
.blur(10)
.threshold()
.toBuffer()

//as a temporary workaround one can do a second pass rather than chaining operations
let twopass = await sharp(onepass)
.threshold()
.toBuffer()

fs.writeFile('blurry_but_not_thresholded.png', onepass)
fs.writeFile('blurry_and_thresholded.png', twopass)

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

test.png

blurry_but_not_thresholded.png

blurry_and_thresholded.png

[lovell]

Hi, your approach to split this task into two passes is correct. (My understanding is that threshold then blur is more generally useful, or at least this was the case when this feature was added in 2015.)

[thot-experiment]

Thanks for the reply. Is there guidance on how this is supposed to work? Intuitively it seems like I should be able to chain things in whatever order I want but this isn't the case? There's some internal order of precedence? Perhaps there's something I missed in the docs? I'm definitely intending to use the operations in the order listed here.

[lovell]

Please see #241 for discussion about future possible API improvements.

[lovell]

I hope this information helped. Please feel free to re-open with more details if further assistance is required.