'use strict'; const assert = require('assert'); const sharp = require('../../'); const fixtures = require('../fixtures'); describe('Image channel extraction', function () { it('Red channel', function (done) { sharp(fixtures.inputJpg) .extractChannel('red') .resize(320, 240) .toBuffer(function (err, data, info) { if (err) throw err; assert.strictEqual(320, info.width); assert.strictEqual(240, info.height); fixtures.assertSimilar(fixtures.expected('extract-red.jpg'), data, done); }); }); it('Green channel', function (done) { sharp(fixtures.inputJpg) .extractChannel('green') .resize(320, 240) .toBuffer(function (err, data, info) { if (err) throw err; assert.strictEqual(320, info.width); assert.strictEqual(240, info.height); fixtures.assertSimilar(fixtures.expected('extract-green.jpg'), data, done); }); }); it('Blue channel', function (done) { sharp(fixtures.inputJpg) .extractChannel('blue') .resize(320, 240) .toBuffer(function (err, data, info) { if (err) throw err; assert.strictEqual(320, info.width); assert.strictEqual(240, info.height); fixtures.assertSimilar(fixtures.expected('extract-blue.jpg'), data, done); }); }); it('Blue channel by number', function (done) { sharp(fixtures.inputJpg) .extractChannel(2) .resize(320, 240) .toBuffer(function (err, data, info) { if (err) throw err; assert.strictEqual(320, info.width); assert.strictEqual(240, info.height); fixtures.assertSimilar(fixtures.expected('extract-blue.jpg'), data, done); }); }); it('With colorspace conversion', function (done) { const output = fixtures.path('output.extract-lch.jpg'); sharp(fixtures.inputJpg) .toColourspace('lch') .extractChannel(1) .resize(320, 240, { fastShrinkOnLoad: false }) .toFile(output, function (err, info) { if (err) throw err; assert.strictEqual(320, info.width); assert.strictEqual(240, info.height); fixtures.assertMaxColourDistance(output, fixtures.expected('extract-lch.jpg'), 9); done(); }); }); it('Alpha from 16-bit PNG', function (done) { const output = fixtures.path('output.extract-alpha-16bit.jpg'); sharp(fixtures.inputPngWithTransparency16bit) .extractChannel(3) .toFile(output, function (err, info) { if (err) throw err; fixtures.assertMaxColourDistance(output, fixtures.expected('extract-alpha-16bit.jpg')); done(); }); }); it('Alpha from 2-channel input', function (done) { const output = fixtures.path('output.extract-alpha-2-channel.png'); sharp(fixtures.inputPngWithGreyAlpha) .extractChannel('alpha') .toColourspace('b-w') .toFile(output, function (err, info) { if (err) throw err; assert.strictEqual(1, info.channels); fixtures.assertMaxColourDistance(output, fixtures.expected('extract-alpha-2-channel.png')); done(); }); }); it('Invalid channel number', function () { assert.throws(function () { sharp(fixtures.inputJpg) .extractChannel(-1); }); }); it('No arguments', function () { assert.throws(function () { sharp(fixtures.inputJpg) .extractChannel(); }); }); it('Non-existant channel', function (done) { sharp(fixtures.inputPng) .extractChannel(1) .toBuffer(function (err) { assert(err instanceof Error); done(); }); }); });