Docs: reorder/highlight optional output properties

docs/api-output.md

@@ -140,20 +140,22 @@ Returns **Sharp**
 
 Use these JPEG options for output image.
 
+Some of these options require the use of a globally-installed libvips compiled with support for mozjpeg.
+
 ### Parameters
 
 -   `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]** 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.optimiseCoding` **[boolean][7]** optimise Huffman coding tables (optional, default `true`)
+    -   `options.optimizeCoding` **[boolean][7]** alternative spelling of optimiseCoding (optional, default `true`)
     -   `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`)
-    -   `options.optimizeScans` **[boolean][7]** alternative spelling of optimiseScans (optional, default `false`)
+    -   `options.optimizeScans` **[boolean][7]** alternative spelling of optimiseScans, requires libvips compiled with support for mozjpeg (optional, default `false`)
-    -   `options.optimiseCoding` **[boolean][7]** optimise Huffman coding tables (optional, default `true`)
-    -   `options.optimizeCoding` **[boolean][7]** alternative spelling of optimiseCoding (optional, default `true`)
     -   `options.quantisationTable` **[number][9]** quantization table to use, integer 0-8, requires libvips compiled with support for mozjpeg (optional, default `0`)
-    -   `options.quantizationTable` **[number][9]** alternative spelling of quantisationTable (optional, default `0`)
+    -   `options.quantizationTable` **[number][9]** alternative spelling of quantisationTable, requires libvips compiled with support for mozjpeg (optional, default `0`)
     -   `options.force` **[boolean][7]** force JPEG output, otherwise attempt to use input format (optional, default `true`)
 
 ### Examples
@@ -179,6 +181,8 @@ Use these PNG options for output image.
 PNG output is always full colour at 8 or 16 bits per pixel.
 Indexed PNG input at 1, 2 or 4 bits per pixel is converted to 8 bits per pixel.
 
+Some of these options require the use of a globally-installed libvips compiled with support for libimagequant (GPL).
+
 ### Parameters
 
 -   `options` **[Object][6]?** 

lib/output.js

@@ -173,6 +173,8 @@ function toFormat (format, options) {
 /**
  * Use these JPEG options for output image.
  *
+ * Some of these options require the use of a globally-installed libvips compiled with support for mozjpeg.
+ *
  * @example
  * // Convert any input to very high quality JPEG output
  * const data = await sharp(input)
@@ -186,14 +188,14 @@ function toFormat (format, 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'] - 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.optimiseCoding=true] - optimise Huffman coding tables
+ * @param {boolean} [options.optimizeCoding=true] - alternative spelling of optimiseCoding
  * @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
- * @param {boolean} [options.optimizeScans=false] - alternative spelling of optimiseScans
+ * @param {boolean} [options.optimizeScans=false] - alternative spelling of optimiseScans, requires libvips compiled with support for mozjpeg
- * @param {boolean} [options.optimiseCoding=true] - optimise Huffman coding tables
- * @param {boolean} [options.optimizeCoding=true] - alternative spelling of optimiseCoding
  * @param {number} [options.quantisationTable=0] - quantization table to use, integer 0-8, requires libvips compiled with support for mozjpeg
- * @param {number} [options.quantizationTable=0] - alternative spelling of quantisationTable
+ * @param {number} [options.quantizationTable=0] - alternative spelling of quantisationTable, requires libvips compiled with support for mozjpeg
  * @param {boolean} [options.force=true] - force JPEG output, otherwise attempt to use input format
  * @returns {Sharp}
  * @throws {Error} Invalid options
@@ -253,6 +255,8 @@ function jpeg (options) {
  * PNG output is always full colour at 8 or 16 bits per pixel.
  * Indexed PNG input at 1, 2 or 4 bits per pixel is converted to 8 bits per pixel.
  *
+ * Some of these options require the use of a globally-installed libvips compiled with support for libimagequant (GPL).
+ *
  * @example
  * // Convert any input to PNG output
  * const data = await sharp(input)