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/*! |
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* bitdepth |
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* Change the bit depth of samples to and from 8, 16, 24, 32 & 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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const f64f32 = new Float32Array(1); |
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/** |
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* Max number of different values for each bit depth. |
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* @enum {number} |
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* @private |
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*/ |
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const MAX_VALUES = { |
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"8": 256, |
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"16": 65536, |
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"24": 16777216, |
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"32": 4294967296, |
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"32f": 1, |
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"64": 1 |
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}; |
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/** |
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* Functions to change the bit depth of a sample. |
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* @enum {Function} |
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* @private |
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*/ |
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const CODECS = { |
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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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*/ |
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"intToInt": function(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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*/ |
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"floatToInt": function(sample, args) { |
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return sample > 0 ? |
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sample * args["newPositive"] : sample * args["newNegative"]; |
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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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*/ |
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"intToFloat": function(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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*/ |
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"floatToFloat": function(sample, args) { |
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if (args["original"] == "64" && args["target"] == "32f") { |
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f64f32[0] = sample; |
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sample = f64f32[0]; |
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} |
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return sample; |
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} |
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}; |
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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", "16", "24", "32", "32f", "64" |
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* @param {string} targetBitDepth The new bit depth of the data. |
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* One of "8", "16", "24", "32", "32f", "64" |
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*/ |
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function toBitDepth(samples, originalBitDepth, targetBitDepth) { |
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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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for (let i=0; i<len; i++) { |
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samples[i] = sign8Bit_(samples[i], originalBitDepth); |
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samples[i] = toFunction( |
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samples[i], |
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{ |
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"oldNegative": MAX_VALUES[originalBitDepth] / 2, |
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"newNegative": MAX_VALUES[targetBitDepth] / 2, |
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"oldPositive": MAX_VALUES[originalBitDepth] / 2 - 1, |
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"newPositive": MAX_VALUES[targetBitDepth] / 2 - 1, |
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"original": originalBitDepth, |
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"target": targetBitDepth |
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} |
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); |
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samples[i] = unsign8Bit_(samples[i], targetBitDepth); |
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} |
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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", "16", "24", "32", "32f", "64" |
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* @param {string} targetBitDepth The new bit depth of the data. |
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* One of "8", "16", "24", "32", "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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let prefix; |
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let suffix; |
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if (["32f", "64"].includes(originalBitDepth)) { |
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prefix = "float"; |
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} else { |
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prefix = "int"; |
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} |
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if (["32f", "64"].includes(targetBitDepth)) { |
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suffix = "Float"; |
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} else { |
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suffix = "Int"; |
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} |
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return CODECS[prefix + "To" + suffix]; |
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} |
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/** |
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* Sign unsigned 8-bit data. |
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* @param {number} sample The sample. |
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* @param {string} originalBitDepth The original bit depth of the data. |
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* One of "8", "16", "24", "32", "32f", "64" |
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* @return {number} |
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* @private |
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*/ |
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function sign8Bit_(sample, originalBitDepth) { |
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if (originalBitDepth == "8") { |
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sample -= 128; |
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} |
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return sample; |
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} |
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/** |
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* Unsign signed 8-bit data. |
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* @param {number} sample The sample. |
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* @param {string} targetBitDepth The target bit depth of the data. |
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* One of "8", "16", "24", "32", "32f", "64" |
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* @return {number} |
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* @private |
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*/ |
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function unsign8Bit_(sample, targetBitDepth) { |
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if (targetBitDepth == "8") { |
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sample += 128; |
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} |
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return sample; |
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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", "16", "24", "32", "32f", "64". |
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* @param {string} targetBitDepth The target bit depth. |
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* Should be one of "8", "16", "24", "32", "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 = ["8", "16", "24", "32", "32f", "64"]; |
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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 = toBitDepth; |
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rochars /
bitdepth
