Improve tint luminance with weighting function (#3859)

Co-authored-by: John Cupitt <jcupitt@gmail.com>

test/unit/tint.js

@@ -8,16 +8,19 @@ const assert = require('assert');
 const sharp = require('../../');
 const fixtures = require('../fixtures');
 
+// Allow for small rounding differences between platforms
+const maxDistance = 6;
+
 describe('Tint', function () {
   it('tints rgb image red', function (done) {
     const output = fixtures.path('output.tint-red.jpg');
     sharp(fixtures.inputJpg)
-      .resize(320, 240, { fastShrinkOnLoad: false })
+      .resize(320, 240)
       .tint('#FF0000')
       .toFile(output, function (err, info) {
         if (err) throw err;
         assert.strictEqual(true, info.size > 0);
-        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-red.jpg'), 18);
+        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-red.jpg'), maxDistance);
         done();
       });
   });
@@ -25,12 +28,12 @@ describe('Tint', function () {
   it('tints rgb image green', function (done) {
     const output = fixtures.path('output.tint-green.jpg');
     sharp(fixtures.inputJpg)
-      .resize(320, 240, { fastShrinkOnLoad: false })
+      .resize(320, 240)
       .tint('#00FF00')
       .toFile(output, function (err, info) {
         if (err) throw err;
         assert.strictEqual(true, info.size > 0);
-        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-green.jpg'), 27);
+        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-green.jpg'), maxDistance);
         done();
       });
   });
@@ -38,12 +41,12 @@ describe('Tint', function () {
   it('tints rgb image blue', function (done) {
     const output = fixtures.path('output.tint-blue.jpg');
     sharp(fixtures.inputJpg)
-      .resize(320, 240, { fastShrinkOnLoad: false })
+      .resize(320, 240)
       .tint('#0000FF')
       .toFile(output, function (err, info) {
         if (err) throw err;
         assert.strictEqual(true, info.size > 0);
-        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-blue.jpg'), 14);
+        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-blue.jpg'), maxDistance);
         done();
       });
   });
@@ -51,13 +54,13 @@ describe('Tint', function () {
   it('tints rgb image with sepia tone', function (done) {
     const output = fixtures.path('output.tint-sepia-hex.jpg');
     sharp(fixtures.inputJpg)
-      .resize(320, 240, { fastShrinkOnLoad: false })
+      .resize(320, 240)
       .tint('#704214')
       .toFile(output, function (err, info) {
         if (err) throw err;
         assert.strictEqual(320, info.width);
         assert.strictEqual(240, info.height);
-        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-sepia.jpg'), 10);
+        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-sepia.jpg'), maxDistance);
         done();
       });
   });
@@ -65,13 +68,13 @@ describe('Tint', function () {
   it('tints rgb image with sepia tone with rgb colour', function (done) {
     const output = fixtures.path('output.tint-sepia-rgb.jpg');
     sharp(fixtures.inputJpg)
-      .resize(320, 240, { fastShrinkOnLoad: false })
+      .resize(320, 240)
       .tint([112, 66, 20])
       .toFile(output, function (err, info) {
         if (err) throw err;
         assert.strictEqual(320, info.width);
         assert.strictEqual(240, info.height);
-        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-sepia.jpg'), 10);
+        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-sepia.jpg'), maxDistance);
         done();
       });
   });
@@ -79,13 +82,13 @@ describe('Tint', function () {
   it('tints rgb image with alpha channel', function (done) {
     const output = fixtures.path('output.tint-alpha.png');
     sharp(fixtures.inputPngRGBWithAlpha)
-      .resize(320, 240, { fastShrinkOnLoad: false })
+      .resize(320, 240)
       .tint('#704214')
       .toFile(output, function (err, info) {
         if (err) throw err;
         assert.strictEqual(320, info.width);
         assert.strictEqual(240, info.height);
-        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-alpha.png'), 10);
+        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-alpha.png'), maxDistance);
         done();
       });
   });
@@ -93,12 +96,12 @@ describe('Tint', function () {
   it('tints cmyk image red', function (done) {
     const output = fixtures.path('output.tint-cmyk.jpg');
     sharp(fixtures.inputJpgWithCmykProfile)
-      .resize(320, 240, { fastShrinkOnLoad: false })
+      .resize(320, 240)
       .tint('#FF0000')
       .toFile(output, function (err, info) {
         if (err) throw err;
         assert.strictEqual(true, info.size > 0);
-        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-cmyk.jpg'), 15);
+        fixtures.assertMaxColourDistance(output, fixtures.expected('tint-cmyk.jpg'), maxDistance);
         done();
       });
   });