DmxUtil.java

/**
 * Copyright (c) 2010-2016 by the respective copyright holders.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
package org.openhab.binding.dmx.internal.core;

import java.math.BigDecimal;

import org.openhab.core.library.types.PercentType;

/**
 * Utility class for converting and calculating DMX values.
 *
 * @author Davy Vanherbergen
 * @since 1.2.0
 */
public class DmxUtil {

    /**
     * Hidden default constructor.
     */
    private DmxUtil() {

    }

    /**
     * Limit a value to the valid DMX range.
     * 
     * @param value
     *            start value
     * @return a value in the 0-255 range
     */
    public static int capDmxValue(int value) {
        if (value > DmxChannel.DMX_MAX_VALUE) {
            return DmxChannel.DMX_MAX_VALUE;
        } else if (value < DmxChannel.DMX_MIN_VALUE) {
            return DmxChannel.DMX_MIN_VALUE;
        } else {
            return value;
        }
    }

    /**
     * Convert a percent type to a 0-255 scale value.
     * 
     * @param pt
     *            percent type to convert
     * @return converted value 0-255
     */
    public static int getByteFromPercentType(PercentType pt) {
        return pt.toBigDecimal().multiply(BigDecimal.valueOf(DmxChannel.DMX_MAX_VALUE))
                .divide(PercentType.HUNDRED.toBigDecimal(), 0, BigDecimal.ROUND_UP).intValue();
    }

    /**
     * Convert a 0-255 scale value to a percent type.
     * 
     * @param pt
     *            percent type to convert
     * @return converted value 0-255
     */
    public static PercentType getPercentTypeFromByte(int value) {
        return new PercentType(BigDecimal.valueOf(value).multiply(BigDecimal.valueOf(100))
                .divide(BigDecimal.valueOf(DmxChannel.DMX_MAX_VALUE), 0, BigDecimal.ROUND_UP).intValue());
    }

    /**
     * For a given RGB value, calculate the missing W value.
     * 
     * @param red
     *            input value
     * @param green
     *            input value
     * @param blue
     *            input value
     * @return white value
     */
    public static int calculateWhite(int red, int green, int blue) {
        int low = (red <= green) ? ((red <= blue) ? red : blue) : ((green <= blue) ? green : blue);
        int high = (red >= green) ? ((red >= blue) ? red : blue) : ((green >= blue) ? green : blue);
        if (high == 0) {
            return 0;
        }
        int saturation = 100 * ((high - low) / high);
        return (DmxChannel.DMX_MAX_VALUE - saturation) / DmxChannel.DMX_MAX_VALUE * (red + green + blue) / 3;
    }

    /**
     * Dim the provided input value to the given output level.
     * 
     * @return dimmed value
     */
    public static int getOutputValue(int input, int outputLevel) {
        BigDecimal value = BigDecimal.valueOf(input);
        return value.multiply(BigDecimal.valueOf(outputLevel))
                .divide(PercentType.HUNDRED.toBigDecimal(), 0, BigDecimal.ROUND_UP).intValue();
    }
}