130 lines
3.5 KiB
JavaScript
130 lines
3.5 KiB
JavaScript
module.exports = async options => {
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let index = 0;
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let error = false;
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let frames = [];
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let interval;
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let seekResolve;
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let currentTime = 0;
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let extractOffsets = false;
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const isNumber = n => {
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return +n + '' === n + '';
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};
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const isTimestamp = timestamp => {
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return isNumber(timestamp) && +timestamp >= 0 && +timestamp <= video.duration;
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};
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const fallbackToDefault = (property, defaultValue) => {
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options[property] = options.hasOwnProperty(property) ? options[property] : defaultValue;
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};
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// Buffer Video Element
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const video = document.createElement('video');
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video.src = options.url;
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video.crossOrigin = 'anonymous';
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video.onseeked = async () => {
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if(seekResolve)
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seekResolve();
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};
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video.onerror = () => {
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error = true;
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};
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while((video.duration === Infinity || isNaN(video.duration)) && video.readyState < 2 && !error) {
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await new Promise(r => setTimeout(r, 100));
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video.currentTime = 10000000 * Math.random();
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}
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// Set options to default values if not set
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fallbackToDefault('format', 'image/png');
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fallbackToDefault('offsets', []);
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fallbackToDefault('startTime', 0);
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fallbackToDefault('endTime', video.duration);
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fallbackToDefault('count', 1);
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// Filter out invalid offsets
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if(options.offsets.constructor !== Array)
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options.offsets = [];
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else
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options.offsets = options.offsets.filter(offset => {
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return isTimestamp(offset);
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});
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if(options.offsets.length !== 0)
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extractOffsets = true;
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// Check if start and end times are valid
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if(!isTimestamp(options.startTime))
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options.startTime = 0;
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if(!isTimestamp(options.endTime))
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options.endTime = video.duration;
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if(options.startTime >= options.endTime) {
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options.startTime = options.endTime;
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options.count = 1;
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}
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// Convert count value to a positive integer (floor() or 0 if string)
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options.count = Math.abs(~~options.count);
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// Starting at startTime + interval and ending at endTime - interval
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interval = (options.endTime - options.startTime) / (options.count + 1);
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// Set Width and Height
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let isWidthSet = options.hasOwnProperty('width');
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let isHeightSet = options.hasOwnProperty('height');
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let videoDimensionRatio = video.videoWidth / video.videoHeight;
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// Reset Width and Height if not valid
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if(isWidthSet && !isNumber(options.width))
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isWidthSet = false;
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if(isHeightSet && !isNumber(options.height))
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isHeightSet = false;
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if(!isWidthSet && !isHeightSet) {
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// Both Width and Height not set
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options.width = 128;
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options.height = options.width / videoDimensionRatio;
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} else if(isWidthSet && !isHeightSet) {
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// Width set but Height not set
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options.height = options.width / videoDimensionRatio;
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} else if(!isWidthSet && isHeightSet) {
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// Height set but Width not set
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options.width = options.height * videoDimensionRatio;
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}
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// Float values
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options.width = +options.width;
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options.height = +options.height;
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// Buffer Canvas Element
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const canvas = document.createElement('canvas');
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const context = canvas.getContext('2d');
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canvas.width = options.width;
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canvas.height = options.height;
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return new Promise(async resolve => {
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if(error)
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resolve([]);
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while(
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(extractOffsets && index < options.offsets.length) ||
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(!extractOffsets && index < options.count)
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) {
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video.currentTime = extractOffsets ? options.offsets[index] : options.startTime + (index + 1) * interval;
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await new Promise(r => seekResolve = r);
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context.clearRect(0, 0, canvas.width, canvas.height);
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context.drawImage(video, 0, 0, canvas.width, canvas.height);
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frames.push(canvas.toDataURL(options.format));
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index ++;
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}
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resolve(frames);
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});
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}; |