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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} originalBitDepth The original bit depth of the data. |
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* One of "8" ... "53", "32f", "64" |
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* @param {!string} targetBitDepth The desired bit depth for the data. |
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* One of "8" ... "53", "32f", "64" |
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*/ |
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function toBitDepth(samples, originalBitDepth, targetBitDepth) { |
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if (originalBitDepth == targetBitDepth) { |
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return samples; |
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} |
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validateBitDepths_(originalBitDepth, targetBitDepth); |
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let toFunction = getBitDepthFunction_(originalBitDepth, targetBitDepth); |
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let len = samples.length; |
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let options = { |
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oldNegative: parseInt( |
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Math.pow(2, parseInt(originalBitDepth, 10)) / 2, 10), |
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newNegative: parseInt( |
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Math.pow(2, parseInt(targetBitDepth, 10)) / 2, 10), |
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oldPositive: parseInt( |
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Math.pow(2, parseInt(originalBitDepth, 10)) / 2 - 1, 10), |
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newPositive: parseInt( |
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Math.pow(2, parseInt(targetBitDepth, 10)) / 2 - 1, 10), |
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original: originalBitDepth, |
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target: targetBitDepth |
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}; |
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for (let i=0; i<len; i++) { |
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samples[i] = originalBitDepth == "8" ? samples[i] - 128 : samples[i]; |
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samples[i] = toFunction( |
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samples[i], |
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options); |
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samples[i] = targetBitDepth == "8" ? samples[i] + 128 : samples[i]; |
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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( |
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(sample / args.oldPositive) * args.newPositive, 10); |
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} else { |
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sample = parseInt( |
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(sample / args.oldNegative) * args.newNegative, 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 sample > 0 ? |
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parseInt(sample * args.newPositive, 10) : |
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parseInt(sample * args.newNegative, 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 ? |
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sample / args.oldPositive : sample / args.oldNegative; |
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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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* @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 floatToFloat_(sample, args) { |
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f64f32_[0] = sample; |
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sample = f64f32_[0]; |
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return sample; |
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} |
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/** |
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* Get the function to change the bit depth of a sample. |
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* @param {!string} originalBitDepth The original bit depth of the data. |
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* One of "8" ... "53", "32f", "64" |
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* @param {!string} targetBitDepth 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_(originalBitDepth, targetBitDepth) { |
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if (["32f", "64"].includes(originalBitDepth)) { |
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if (["32f", "64"].includes(targetBitDepth)) { |
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return floatToFloat_; |
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} else { |
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return floatToInt_; |
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} |
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} else { |
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if (["32f", "64"].includes(targetBitDepth)) { |
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return intToFloat_; |
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} else { |
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return intToInt_; |
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} |
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} |
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} |
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/** |
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* Validate the bit depth. |
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* @param {!string} originalBitDepth The original bit depth. |
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* Should be one of "8" ... "53", "32f", "64". |
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* @param {!string} targetBitDepth The target bit depth. |
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* Should be one of "8" ... "53", "32f", "64". |
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* @throws {Error} If any argument does not meet the criteria. |
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* @return {!boolean} |
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* @private |
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*/ |
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function validateBitDepths_(originalBitDepth, targetBitDepth) { |
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let validBitDepths = ["32f", "64"]; |
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for (let i=8; i<54; i++) { |
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validBitDepths.push(i.toString()); |
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} |
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if (validBitDepths.indexOf(originalBitDepth) == -1 || |
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validBitDepths.indexOf(targetBitDepth) == -1) { |
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throw new Error("Invalid bit depth."); |
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} |
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return true; |
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} |
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module.exports = toBitDepth; |
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153
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module.exports.toBitDepth = toBitDepth; |
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