Expose control over CPU effort for palette PNG #2541

docs/api-output.md

@@ -243,6 +243,7 @@ Set `palette` to `true` for slower, indexed PNG output.
     *   `options.adaptiveFiltering` **[boolean][7]** use adaptive row filtering (optional, default `false`)
     *   `options.palette` **[boolean][7]** quantise to a palette-based image with alpha transparency support (optional, default `false`)
     *   `options.quality` **[number][9]** use the lowest number of colours needed to achieve given quality, sets `palette` to `true` (optional, default `100`)
+    *   `options.effort` **[number][9]** CPU effort, between 1 (fastest) and 10 (slowest), sets `palette` to `true` (optional, default `7`)
     *   `options.colours` **[number][9]** maximum number of palette entries, sets `palette` to `true` (optional, default `256`)
     *   `options.colors` **[number][9]** alternative spelling of `options.colours`, sets `palette` to `true` (optional, default `256`)
     *   `options.dither` **[number][9]** level of Floyd-Steinberg error diffusion, sets `palette` to `true` (optional, default `1.0`)

docs/changelog.md

@@ -10,6 +10,9 @@ Requires libvips v8.12.0
 
 * Reduce minimum Linux ARM64v8 glibc requirement to 2.17.
 
+* Expose control over CPU effort for palette-based PNG output.
+  [#2541](https://github.com/lovell/sharp/issues/2541)
+
 * Ensure 16-bit PNG output uses correct bitdepth.
   [#2958](https://github.com/lovell/sharp/pull/2958)
   [@gforge](https://github.com/gforge)

lib/constructor.js

@@ -234,6 +234,7 @@ const Sharp = function (input, options) {
     pngAdaptiveFiltering: false,
     pngPalette: false,
     pngQuality: 100,
+    pngEffort: 7,
     pngBitdepth: 8,
     pngDither: 1,
     jp2Quality: 80,

lib/output.js

@@ -373,6 +373,7 @@ function jpeg (options) {
  * @param {boolean} [options.adaptiveFiltering=false] - use adaptive row filtering
  * @param {boolean} [options.palette=false] - quantise to a palette-based image with alpha transparency support
  * @param {number} [options.quality=100] - use the lowest number of colours needed to achieve given quality, sets `palette` to `true`
+ * @param {number} [options.effort=7] - CPU effort, between 1 (fastest) and 10 (slowest), sets `palette` to `true`
  * @param {number} [options.colours=256] - maximum number of palette entries, sets `palette` to `true`
  * @param {number} [options.colors=256] - alternative spelling of `options.colours`, sets `palette` to `true`
  * @param {number} [options.dither=1.0] - level of Floyd-Steinberg error diffusion, sets `palette` to `true`
@@ -397,7 +398,7 @@ function png (options) {
     }
     if (is.defined(options.palette)) {
       this._setBooleanOption('pngPalette', options.palette);
-    } else if (is.defined(options.quality) || is.defined(options.colours || options.colors) || is.defined(options.dither)) {
+    } else if ([options.quality, options.effort, options.colours, options.colors, options.dither].some(is.defined)) {
       this._setBooleanOption('pngPalette', true);
     }
     if (this.options.pngPalette) {
@@ -408,6 +409,13 @@ function png (options) {
           throw is.invalidParameterError('quality', 'integer between 0 and 100', options.quality);
         }
       }
+      if (is.defined(options.effort)) {
+        if (is.integer(options.effort) && is.inRange(options.effort, 1, 10)) {
+          this.options.pngEffort = options.effort;
+        } else {
+          throw is.invalidParameterError('effort', 'integer between 1 and 10', options.effort);
+        }
+      }
       const colours = options.colours || options.colors;
       if (is.defined(colours)) {
         if (is.integer(colours) && is.inRange(colours, 2, 256)) {

src/pipeline.cc

@@ -824,6 +824,7 @@ class PipelineWorker : public Napi::AsyncWorker {
             ->set("filter", baton->pngAdaptiveFiltering ? VIPS_FOREIGN_PNG_FILTER_ALL : VIPS_FOREIGN_PNG_FILTER_NONE)
             ->set("palette", baton->pngPalette)
             ->set("Q", baton->pngQuality)
+            ->set("effort", baton->pngEffort)
             ->set("bitdepth", sharp::Is16Bit(image.interpretation()) ? 16 : baton->pngBitdepth)
             ->set("dither", baton->pngDither)));
           baton->bufferOut = static_cast<char*>(area->data);
@@ -994,6 +995,7 @@ class PipelineWorker : public Napi::AsyncWorker {
             ->set("palette", baton->pngPalette)
             ->set("Q", baton->pngQuality)
             ->set("bitdepth", sharp::Is16Bit(image.interpretation()) ? 16 : baton->pngBitdepth)
+            ->set("effort", baton->pngEffort)
             ->set("dither", baton->pngDither));
           baton->formatOut = "png";
         } else if (baton->formatOut == "webp" || (mightMatchInput && isWebp) ||
@@ -1470,6 +1472,7 @@ Napi::Value pipeline(const Napi::CallbackInfo& info) {
   baton->pngAdaptiveFiltering = sharp::AttrAsBool(options, "pngAdaptiveFiltering");
   baton->pngPalette = sharp::AttrAsBool(options, "pngPalette");
   baton->pngQuality = sharp::AttrAsUint32(options, "pngQuality");
+  baton->pngEffort = sharp::AttrAsUint32(options, "pngEffort");
   baton->pngBitdepth = sharp::AttrAsUint32(options, "pngBitdepth");
   baton->pngDither = sharp::AttrAsDouble(options, "pngDither");
   baton->jp2Quality = sharp::AttrAsUint32(options, "jp2Quality");

src/pipeline.h

@@ -147,6 +147,7 @@ struct PipelineBaton {
   bool pngAdaptiveFiltering;
   bool pngPalette;
   int pngQuality;
+  int pngEffort;
   int pngBitdepth;
   double pngDither;
   int jp2Quality;
@@ -287,6 +288,7 @@ struct PipelineBaton {
     pngAdaptiveFiltering(false),
     pngPalette(false),
     pngQuality(100),
+    pngEffort(7),
     pngBitdepth(8),
     pngDither(1.0),
     jp2Quality(80),

test/unit/png.js

@@ -143,8 +143,8 @@ describe('PNG', function () {
   it('Valid PNG libimagequant quality value produces image of same size or smaller', function () {
     const inputPngBuffer = fs.readFileSync(fixtures.inputPng);
     return Promise.all([
-      sharp(inputPngBuffer).resize(10).png({ quality: 80 }).toBuffer(),
+      sharp(inputPngBuffer).resize(10).png({ effort: 1, quality: 80 }).toBuffer(),
-      sharp(inputPngBuffer).resize(10).png({ quality: 100 }).toBuffer()
+      sharp(inputPngBuffer).resize(10).png({ effort: 1, quality: 100 }).toBuffer()
     ]).then(function (data) {
       assert.strictEqual(true, data[0].length <= data[1].length);
     });
@@ -156,6 +156,12 @@ describe('PNG', function () {
     });
   });
 
+  it('Invalid effort value throws error', () => {
+    assert.throws(() => {
+      sharp().png({ effort: 0.1 });
+    });
+  });
+
   it('Valid PNG libimagequant colours value produces image of same size or smaller', function () {
     const inputPngBuffer = fs.readFileSync(fixtures.inputPng);
     return Promise.all([