1 |
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2 |
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3 | const { spawn } = require('child_process')
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4 |
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5 | /**
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6 | * Parse a size string (eg. '240x?')
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7 | * @func parseSize
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8 | * @param {String} sizeStr A string in the form of '240x100' or '50%'
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9 | * @returns {Object} Object containing numeric values of the width and height
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10 | * of the thumbnail, or the scaling percentage
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11 | * @throws {Error} Throws on malformed size string
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12 | */
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13 | function parseSize (sizeStr) {
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14 | const invalidSizeString = new Error('Invalid size string')
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15 | const percentRegex = /(\d+)%/g
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16 | const sizeRegex = /(\d+|\?)x(\d+|\?)/g
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17 | let size
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18 |
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19 | const percentResult = percentRegex.exec(sizeStr)
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20 | const sizeResult = sizeRegex.exec(sizeStr)
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21 |
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22 | if (percentResult) {
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23 | size = { percentage: Number.parseInt(percentResult[1]) }
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24 | } else if (sizeResult) {
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25 | const sizeValues = sizeResult.map(x => x === '?' ? null : Number.parseInt(x))
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26 |
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27 | size = {
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28 | width: sizeValues[1],
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29 | height: sizeValues[2]
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30 | }
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31 | } else {
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32 | throw invalidSizeString
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33 | }
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34 |
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35 | if (size.width === null && size.height === null) {
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36 | throw invalidSizeString
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37 | }
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38 |
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39 | return size
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40 | }
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41 |
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42 | /**
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43 | * Return an array of string arguments to be passed to ffmpeg
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44 | * @func buildArgs
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45 | * @param {String} input The input argument for ffmpeg
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46 | * @param {String} output The output path for the generated thumbnail
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47 | * @param {Object} size A size object returned from parseSize
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48 | * @param {Number} [size.height] The thumbnail height, in pixels
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49 | * @param {Number} [size.width] The thumbnail width, in pixels
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50 | * @param {Number} [size.percentage] The thumbnail scaling percentage
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51 | * @param {String} seek The time to seek, formatted as hh:mm:ss[.ms]
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52 | * @returns {Array<string>} Array of arguments for ffmpeg
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53 | */
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54 | function buildArgs (input, output, { width, height, percentage }, seek) {
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55 | const scaleArg = (percentage)
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56 | ? `-vf scale=iw*${percentage / 100}:ih*${percentage / 100}`
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57 | : `-vf scale=${width || -1}:${height || -1}`
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58 |
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59 | return [
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60 | '-y',
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61 | `-i ${input}`,
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62 | '-vframes 1',
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63 | `-ss ${seek}`,
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64 | scaleArg,
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65 | output
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66 | ]
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67 | }
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68 |
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69 | /**
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70 | * Spawn an instance of ffmpeg and generate a thumbnail
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71 | * @func ffmpegExecute
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72 | * @param {String} path The path of the ffmpeg binary
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73 | * @param {Array<string>} args An array of arguments for ffmpeg
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74 | * @param {stream.Readable} [rstream] A readable stream to pipe data to
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75 | * the standard input of ffmpeg
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76 | * @param {stream.Writable} [wstream] A writable stream to receive data from
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77 | * the standard output of ffmpeg
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78 | * @returns {Promise} Promise that resolves once thumbnail is generated
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79 | */
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80 | function ffmpegExecute (path, args, rstream, wstream) {
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81 | const ffmpeg = spawn(path, args, { shell: true })
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82 | let stderr = ''
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83 |
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84 | return new Promise((resolve, reject) => {
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85 | if (rstream) {
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86 | rstream.pipe(ffmpeg.stdin)
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87 | }
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88 | if (wstream) {
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89 | ffmpeg.stdout.pipe(wstream)
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90 | }
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91 |
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92 | ffmpeg.stderr.on('data', (data) => {
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93 | stderr += data.toString()
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94 | })
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95 | ffmpeg.stderr.on('error', (err) => {
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96 | reject(err)
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97 | })
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98 | ffmpeg.on('exit', (code, signal) => {
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99 | if (code !== 0) {
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100 | const err = new Error(`ffmpeg exited ${code}\nffmpeg stderr:\n\n${stderr}`)
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101 | reject(err)
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102 | }
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103 | })
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104 | ffmpeg.on('close', resolve)
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105 | })
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106 | }
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107 |
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108 | /**
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109 | * Spawn an instance of ffmpeg and generate a thumbnail
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110 | * @func ffmpegStreamExecute
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111 | * @param {String} path The path of the ffmpeg binary
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112 | * @param {Array<string>} args An array of arguments for ffmpeg
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113 | * @param {stream.Readable} [rstream] A readable stream to pipe data to
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114 | * the standard input of ffmpeg
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115 | * @returns {Promise} Promise that resolves to ffmpeg stdout
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116 | */
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117 | function ffmpegStreamExecute (path, args, rstream) {
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118 | const ffmpeg = spawn(path, args, { shell: true })
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119 |
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120 | if (rstream) {
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121 | rstream.pipe(ffmpeg.stdin)
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122 | }
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123 |
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124 | return Promise.resolve(ffmpeg.stdout)
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125 | }
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126 |
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127 | /**
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128 | * Generates a thumbnail from the first frame of a video file
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129 | * @func genThumbnail
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130 | * @param {String|stream.Readable} input Path to video, or a read stream
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131 | * @param {String|stream.Writeable} output Output path of the thumbnail
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132 | * @param {String} size The size of the thumbnail, eg. '240x240'
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133 | * @param {Object} [config={}] A configuration object
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134 | * @param {String} [config.path='ffmpeg'] Path of the ffmpeg binary
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135 | * @param {String} [config.seek='00:00:00'] Time to seek for videos
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136 | * @returns {Promise} Resolves on completion, or rejects on error
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137 | */
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138 | function genThumbnail (input, output, size, config = {}) {
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139 | const ffmpegPath = config.path || process.env.FFMPEG_PATH || 'ffmpeg'
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140 | const seek = config.seek || '00:00:00'
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141 | const rstream = typeof input === 'string' ? null : input
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142 | const wstream = typeof output === 'string' ? null : output
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143 |
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144 | const parsedSize = parseSize(size)
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145 | const args = buildArgs(
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146 | typeof input === 'string' ? `"${input}"` : 'pipe:0',
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147 | typeof output === 'string' ? `"${output}"` : '-f singlejpeg pipe:1',
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148 | parsedSize,
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149 | seek
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150 | )
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151 |
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152 | if (output === null) {
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153 | return ffmpegStreamExecute(ffmpegPath, args, rstream)
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154 | }
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155 |
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156 | return ffmpegExecute(ffmpegPath, args, rstream, wstream)
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157 | }
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158 |
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159 | module.exports = genThumbnail
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