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/** |
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* bitdepth |
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* Change the resolution of samples to and from 8, 11, 12, 16, 20, 24, 32, 48 & 64-bit. |
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* Copyright (c) 2017-2018 Rafael da Silva Rocha. |
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* https://github.com/rochars/bitdepth |
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* |
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*/ |
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/** @private */ |
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const f64f32_ = new Float32Array(1); |
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/** |
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* Change the bit depth of the data in a array. |
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* The input array is modified in-place. |
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* @param {!Array<number>} samples The samples. |
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* @param {!string} original The original bit depth of the data. |
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* One of "8" ... "53", "32f", "64" |
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* @param {!string} target The desired bit depth for the data. |
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* One of "8" ... "53", "32f", "64" |
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* @param {Array<number>=} outputArray An optional array to write converted samples to. |
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* Useful for writing to typed arrays. |
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*/ |
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function toBitDepth(samples, original, target, outputArray) { |
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validateBitDepth_(original); |
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validateBitDepth_(target); |
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outputArray = outputArray || samples; |
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let toFunction = getBitDepthFunction_(original, target); |
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let options = { |
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oldMin: Math.pow(2, parseInt(original, 10)) / 2, |
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newMin: Math.pow(2, parseInt(target, 10)) / 2, |
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oldMax: (Math.pow(2, parseInt(original, 10)) / 2) - 1, |
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newMax: (Math.pow(2, parseInt(target, 10)) / 2) - 1, |
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}; |
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const len = samples.length; |
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// sign the samples if original is 8-bit |
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if (original == "8") { |
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for (let i=0; i<len; i++) { |
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outputArray[i] = samples[i] -= 128; |
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} |
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} |
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// change the resolution of the samples |
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for (let i=0; i<len; i++) { |
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outputArray[i] = toFunction(samples[i], options); |
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} |
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// unsign the samples if target is 8-bit |
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if (target == "8") { |
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for (let i=0; i<len; i++) { |
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outputArray[i] = outputArray[i] += 128; |
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} |
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} |
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} |
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/** |
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* Change the bit depth from int to int. |
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* @param {!number} sample The sample. |
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* @param {!Object} args Data about the original and target bit depths. |
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* @return {!number} |
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* @private |
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*/ |
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function intToInt_(sample, args) { |
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if (sample > 0) { |
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sample = parseInt((sample / args.oldMax) * args.newMax, 10); |
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} else { |
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sample = parseInt((sample / args.oldMin) * args.newMin, 10); |
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} |
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return sample; |
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} |
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/** |
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* Change the bit depth from float to int. |
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* @param {!number} sample The sample. |
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* @param {!Object} args Data about the original and target bit depths. |
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* @return {!number} |
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* @private |
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*/ |
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function floatToInt_(sample, args) { |
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return parseInt( |
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sample > 0 ? sample * args.newMax : sample * args.newMin, 10); |
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} |
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/** |
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* Change the bit depth from int to float. |
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* @param {!number} sample The sample. |
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* @param {!Object} args Data about the original and target bit depths. |
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* @return {!number} |
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* @private |
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*/ |
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function intToFloat_(sample, args) { |
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return sample > 0 ? sample / args.oldMax : sample / args.oldMin; |
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} |
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/** |
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* Change the bit depth from float to float. |
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* @param {!number} sample The sample. |
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* @return {!number} |
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* @private |
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*/ |
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function floatToFloat_(sample) { |
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f64f32_[0] = sample; |
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return f64f32_[0]; |
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} |
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/** |
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* Return the function to change the bit depth of a sample. |
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* @param {!string} original The original bit depth of the data. |
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* One of "8" ... "53", "32f", "64" |
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* @param {!string} target The new bit depth of the data. |
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* One of "8" ... "53", "32f", "64" |
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* @return {!Function} |
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* @private |
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*/ |
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function getBitDepthFunction_(original, target) { |
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/** @type {!Function} */ |
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let func; |
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if (["32f", "64"].includes(original)) { |
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if (["32f", "64"].includes(target)) { |
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func = floatToFloat_; |
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} else { |
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func = floatToInt_; |
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} |
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} else { |
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if (["32f", "64"].includes(target)) { |
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return intToFloat_; |
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} else { |
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func = intToInt_; |
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} |
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} |
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if (original == target) { |
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func = function(x,y) {return x;}; |
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} |
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return func; |
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} |
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/** |
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* Validate the bit depth. |
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* @param {!string} bitDepth The original bit depth. |
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* Should be one of "8" ... "53", "32f" or "64". |
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* @throws {Error} If any argument does not meet the criteria. |
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* @private |
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*/ |
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function validateBitDepth_(bitDepth) { |
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if ((bitDepth != "32f" && bitDepth != "64") && |
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(parseInt(bitDepth, 10) < "8" || parseInt(bitDepth, 10) > "53")) { |
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throw new Error("Invalid bit depth."); |
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} |
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} |
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module.exports = toBitDepth; |
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module.exports.toBitDepth = toBitDepth; |
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rochars /
bitdepth
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