js-dicom/src/ImageUtility/internal/getVOILUT.js

this is js-dicom

/**
 * This module generates a VOI LUT
 */

    function generateLinearVOILUT(windowWidth, windowCenter) {
        return function(modalityLutValue) {
            return (((modalityLutValue - (windowCenter)) / (windowWidth) + 0.5) * 255.0);
        }
    }

    function generateNonLinearVOILUT(voiLUT) {
        var shift = voiLUT.numBitsPerEntry - 8;
        var minValue = voiLUT.lut[0] >> shift;
        var maxValue = voiLUT.lut[voiLUT.lut.length -1] >> shift;
        var maxValueMapped = voiLUT.firstValueMapped + voiLUT.lut.length - 1;
        return function(modalityLutValue) {
            if(modalityLutValue < voiLUT.firstValueMapped) {
                return minValue;
            }
            else if(modalityLutValue >= maxValueMapped)
            {
                return maxValue;
            }
            else
            {
                return voiLUT.lut[modalityLutValue - voiLUT.firstValueMapped] >> shift;
            }
        }
    }

    function getVOILUT(windowWidth, windowCenter, voiLUT) {
        if(voiLUT) {
            return generateNonLinearVOILUT(voiLUT);
        } else {
            return generateLinearVOILUT(windowWidth, windowCenter);
        }
    }

    // Module exports
    export default getVOILUT;