feat: add blur precision

docs/api-operation.md

@@ -231,7 +231,7 @@ const output = await sharp(input).median(5).toBuffer();
 
 
 ## blur
-> blur([sigma]) ⇒ <code>Sharp</code>
+> blur([options]) ⇒ <code>Sharp</code>
 
 Blur the image.
 
@@ -245,9 +245,11 @@ When a `sigma` is provided, performs a slower, more accurate Gaussian blur.
 - <code>Error</code> Invalid parameters
 
 
-| Param | Type | Description |
-| --- | --- | --- |
-| [sigma] | <code>number</code> | a value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`. |
+| Param | Type | Default | Description |
+| --- | --- | --- | --- |
+| [options] | <code>Object</code> \| <code>number</code> \| <code>Boolean</code> |  |  |
+| [options.sigma] | <code>number</code> |  | a value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`. |
+| [options.precision] | <code>string</code> | <code>&quot;&#x27;integer&#x27;&quot;</code> | How accurate the operation should be, one of: integer, float, approximate. |
 
 **Example**  
 ```js

lib/constructor.js

@@ -226,6 +226,7 @@ const Sharp = function (input, options) {
     negateAlpha: true,
     medianSize: 0,
     blurSigma: 0,
+    precision: 'integer',
     sharpenSigma: 0,
     sharpenM1: 1,
     sharpenM2: 2,

lib/index.d.ts

@@ -464,7 +464,7 @@ declare namespace sharp {
          * @throws {Error} Invalid parameters
          * @returns A sharp instance that can be used to chain operations
          */
-        blur(sigma?: number | boolean): Sharp;
+        blur(sigma?: number | boolean | BlurOptions): Sharp;
 
         /**
          * Merge alpha transparency channel, if any, with background.
@@ -1342,6 +1342,15 @@ declare namespace sharp {
         background?: Color | undefined;
     }
 
+    type Precision = 'integer' | 'float' | 'approximate';
+
+    interface BlurOptions {
+        /** A value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2` */
+        sigma: number;
+        /** How accurate the operation should be, one of: integer, float, approximate. (optional, default "integer") */
+        precision?: Precision | undefined;
+    }
+
     interface FlattenOptions {
         /** background colour, parsed by the color module, defaults to black. (optional, default {r:0,g:0,b:0}) */
         background?: Color | undefined;

lib/operation.js

@@ -6,6 +6,17 @@
 const color = require('color');
 const is = require('./is');
 
+/**
+ * How accurate an operation should be.
+ * @member
+ * @private
+ */
+const vipsPrecision = {
+  integer: 'integer',
+  float: 'float',
+  approximate: 'approximate'
+};
+
 /**
  * Rotate the output image by either an explicit angle
  * or auto-orient based on the EXIF `Orientation` tag.
@@ -367,23 +378,43 @@ function median (size) {
  *   .blur(5)
  *   .toBuffer();
  *
- * @param {number} [sigma] a value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
+ * @param {Object|number|Boolean} [options]
+ * @param {number} [options.sigma] a value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
+ * @param {string} [options.precision='integer'] How accurate the operation should be, one of: integer, float, approximate.
  * @returns {Sharp}
  * @throws {Error} Invalid parameters
  */
-function blur (sigma) {
-  if (!is.defined(sigma)) {
+function blur (options) {
+  let sigma;
+  if (is.number(options)) {
+    sigma = options;
+  } else if (is.plainObject(options)) {
+    if (!is.number(options.sigma)) {
+      throw is.invalidParameterError('options.sigma', 'number between 0.3 and 1000', sigma);
+    }
+    sigma = options.sigma;
+    if ('precision' in options) {
+      if (is.string(vipsPrecision[options.precision])) {
+        this.options.precision = vipsPrecision[options.precision];
+      } else {
+        throw is.invalidParameterError('precision', 'one of: integer, float, approximate', options.precision);
+      }
+    }
+  }
+
+  if (!is.defined(options)) {
     // No arguments: default to mild blur
     this.options.blurSigma = -1;
-  } else if (is.bool(sigma)) {
+  } else if (is.bool(options)) {
     // Boolean argument: apply mild blur?
-    this.options.blurSigma = sigma ? -1 : 0;
+    this.options.blurSigma = options ? -1 : 0;
   } else if (is.number(sigma) && is.inRange(sigma, 0.3, 1000)) {
     // Numeric argument: specific sigma
     this.options.blurSigma = sigma;
   } else {
     throw is.invalidParameterError('sigma', 'number between 0.3 and 1000', sigma);
   }
+
   return this;
 }
 

src/operations.cc

@@ -144,7 +144,7 @@ namespace sharp {
   /*
    * Gaussian blur. Use sigma of -1.0 for fast blur.
    */
-  VImage Blur(VImage image, double const sigma) {
+  VImage Blur(VImage image, double const sigma, VipsPrecision precision) {
     if (sigma == -1.0) {
       // Fast, mild blur - averages neighbouring pixels
       VImage blur = VImage::new_matrixv(3, 3,
@@ -155,7 +155,8 @@ namespace sharp {
       return image.conv(blur);
     } else {
       // Slower, accurate Gaussian blur
-      return StaySequential(image).gaussblur(sigma);
+      return StaySequential(image).gaussblur(sigma, VImage::option()
+        ->set("precision", precision));
     }
   }
 

src/operations.h

@@ -47,7 +47,7 @@ namespace sharp {
   /*
    * Gaussian blur. Use sigma of -1.0 for fast blur.
    */
-  VImage Blur(VImage image, double const sigma);
+  VImage Blur(VImage image, double const sigma, VipsPrecision precision);
 
   /*
    * Convolution with a kernel.

src/pipeline.cc

@@ -592,7 +592,7 @@ class PipelineWorker : public Napi::AsyncWorker {
 
       // Blur
       if (shouldBlur) {
-        image = sharp::Blur(image, baton->blurSigma);
+        image = sharp::Blur(image, baton->blurSigma, baton->precision);
       }
 
       // Unflatten the image
@@ -1541,6 +1541,7 @@ Napi::Value pipeline(const Napi::CallbackInfo& info) {
   baton->negate = sharp::AttrAsBool(options, "negate");
   baton->negateAlpha = sharp::AttrAsBool(options, "negateAlpha");
   baton->blurSigma = sharp::AttrAsDouble(options, "blurSigma");
+  baton->precision = sharp::AttrAsEnum<VipsPrecision>(options, "precision", VIPS_TYPE_PRECISION);
   baton->brightness = sharp::AttrAsDouble(options, "brightness");
   baton->saturation = sharp::AttrAsDouble(options, "saturation");
   baton->hue = sharp::AttrAsInt32(options, "hue");

src/pipeline.h

@@ -78,6 +78,7 @@ struct PipelineBaton {
   bool negate;
   bool negateAlpha;
   double blurSigma;
+  VipsPrecision precision;
   double brightness;
   double saturation;
   int hue;

test/unit/blur.js

@@ -35,6 +35,19 @@ describe('Blur', function () {
       });
   });
 
+  it('specific options.sigma 10', function (done) {
+    sharp(fixtures.inputJpg)
+      .resize(320, 240)
+      .blur({ sigma: 10 })
+      .toBuffer(function (err, data, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(320, info.width);
+        assert.strictEqual(240, info.height);
+        fixtures.assertSimilar(fixtures.expected('blur-10.jpg'), data, done);
+      });
+  });
+
   it('specific radius 0.3', function (done) {
     sharp(fixtures.inputJpg)
       .resize(320, 240)
@@ -91,4 +104,33 @@ describe('Blur', function () {
           });
       });
   });
+
+  it('invalid precision', function () {
+    assert.throws(function () {
+      sharp(fixtures.inputJpg).blur({ sigma: 1, precision: 'invalid' });
+    });
+  });
+
+  it('specific radius 10 and precision approximate', async () => {
+    const approximate = await sharp(fixtures.inputJpg)
+      .resize(320, 240)
+      .blur({ sigma: 10, precision: 'approximate' })
+      .toBuffer();
+    const integer = await await sharp(fixtures.inputJpg)
+      .resize(320, 240)
+      .blur(10)
+      .toBuffer();
+
+    assert.notDeepEqual(approximate, integer);
+
+    await new Promise(resolve => {
+      fixtures.assertSimilar(fixtures.expected('blur-10.jpg'), approximate, resolve);
+    });
+  });
+
+  it('options.sigma is required if options object is passed', function () {
+    assert.throws(function () {
+      sharp(fixtures.inputJpg).blur({ precision: 'invalid' });
+    });
+  });
 });