Docs: clarify how to achieve 16-bit PNG output

lovell · Feb 14, 2024 · 0eb5769 · 0eb5769
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diff --git a/docs/api-output.md b/docs/api-output.md
@@ -367,10 +367,14 @@ const data = await sharp(input)
 
 Use these PNG options for output image.
 
-By default, PNG output is full colour at 8 or 16 bits per pixel.
+By default, PNG output is full colour at 8 bits per pixel.
+
 Indexed PNG input at 1, 2 or 4 bits per pixel is converted to 8 bits per pixel.
 Set `palette` to `true` for slower, indexed PNG output.
 
+For 16 bits per pixel output, convert to `rgb16` via
+[toColourspace](/api-colour#tocolourspace).
+
 
 **Throws**:
 
@@ -405,6 +409,14 @@ const data = await sharp(input)
   .png({ palette: true })
   .toBuffer();
 ```
+**Example**  
+```js
+// Output 16 bits per pixel RGB(A)
+const data = await sharp(input)
+ .toColourspace('rgb16')
+ .png()
+ .toBuffer();
+```
 
 
 ## webp

diff --git a/lib/output.js b/lib/output.js
@@ -504,10 +504,14 @@ function jpeg (options) {
 /**
  * Use these PNG options for output image.
  *
- * By default, PNG output is full colour at 8 or 16 bits per pixel.
+ * By default, PNG output is full colour at 8 bits per pixel.
+ *
  * Indexed PNG input at 1, 2 or 4 bits per pixel is converted to 8 bits per pixel.
  * Set `palette` to `true` for slower, indexed PNG output.
  *
+ * For 16 bits per pixel output, convert to `rgb16` via
+ * {@link /api-colour#tocolourspace|toColourspace}.
+ *
  * @example
  * // Convert any input to full colour PNG output
  * const data = await sharp(input)
@@ -520,6 +524,13 @@ function jpeg (options) {
  *   .png({ palette: true })
  *   .toBuffer();
  *
+ * @example
+ * // Output 16 bits per pixel RGB(A)
+ * const data = await sharp(input)
+ *  .toColourspace('rgb16')
+ *  .png()
+ *  .toBuffer();
+ *
  * @param {Object} [options]
  * @param {boolean} [options.progressive=false] - use progressive (interlace) scan
  * @param {number} [options.compressionLevel=6] - zlib compression level, 0 (fastest, largest) to 9 (slowest, smallest)