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Docs: clarify JPEG quality/chromaSubsampling interdependence

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Lovell Fuller 2020-03-26 20:22:47 +00:00
parent 8bd8709f2b
commit ecd01afad3
2 changed files with 2 additions and 2 deletions
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docs/api-output.md
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@ -143,7 +143,7 @@ Use these JPEG options for output image.
- `options` **[Object][6]?** output options
- `options.quality` **[Number][9]** quality, integer 1-100 (optional, default `80`)
- `options.progressive` **[Boolean][7]** use progressive (interlace) scan (optional, default `false`)
- `options.chromaSubsampling` **[String][2]** set to '4:4:4' to prevent chroma subsampling when quality <= 90 (optional, default `'4:2:0'`)
- `options.chromaSubsampling` **[String][2]** for quality < 90, set to '4:4:4' to prevent chroma subsampling otherwise defaults to '4:2:0' (use chroma subsampling); for quality >= 90 chroma is never subsampled (optional, default `'4:2:0'`)
- `options.trellisQuantisation` **[Boolean][7]** apply trellis quantisation, requires libvips compiled with support for mozjpeg (optional, default `false`)
- `options.overshootDeringing` **[Boolean][7]** apply overshoot deringing, requires libvips compiled with support for mozjpeg (optional, default `false`)
- `options.optimiseScans` **[Boolean][7]** optimise progressive scans, forces progressive, requires libvips compiled with support for mozjpeg (optional, default `false`)

2
lib/output.js
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@ -183,7 +183,7 @@ function toFormat (format, options) {
* @param {Object} [options] - output options
* @param {Number} [options.quality=80] - quality, integer 1-100
* @param {Boolean} [options.progressive=false] - use progressive (interlace) scan
* @param {String} [options.chromaSubsampling='4:2:0'] - set to '4:4:4' to prevent chroma subsampling when quality <= 90
* @param {String} [options.chromaSubsampling='4:2:0'] - for quality < 90, set to '4:4:4' to prevent chroma subsampling otherwise defaults to '4:2:0' (use chroma subsampling); for quality >= 90 chroma is never subsampled
* @param {Boolean} [options.trellisQuantisation=false] - apply trellis quantisation, requires libvips compiled with support for mozjpeg
* @param {Boolean} [options.overshootDeringing=false] - apply overshoot deringing, requires libvips compiled with support for mozjpeg
* @param {Boolean} [options.optimiseScans=false] - optimise progressive scans, forces progressive, requires libvips compiled with support for mozjpeg