Java tutorial
/******************************************************************************* * Copyright (c) 2004, 2015 IBM Corporation and others. * 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 * * Contributors: * IBM Corporation - initial API and implementation * Lars Vogel <Lars.Vogel@vogella.com> - Bug 472654 *******************************************************************************/ package org.eclipse.ui.themes; import java.lang.reflect.Field; import java.lang.reflect.Modifier; import java.util.ArrayList; import org.eclipse.jface.resource.DataFormatException; import org.eclipse.jface.resource.StringConverter; import org.eclipse.swt.SWT; import org.eclipse.swt.graphics.RGB; import org.eclipse.swt.widgets.Display; /** * Useful color utilities. * * @since 3.0 - initial release * @since 3.2 - public API */ public final class ColorUtil { private static Field[] cachedFields; /** * Process the given string and return a corresponding RGB object. * * @param value * the SWT constant <code>String</code> * @return the value of the SWT constant, or <code>SWT.COLOR_BLACK</code> * if it could not be determined */ private static RGB process(String value) { Field[] fields = getFields(); try { for (int i = 0; i < fields.length; i++) { Field field = fields[i]; if (field.getName().equals(value)) { return getSystemColor(field.getInt(null)); } } } catch (IllegalArgumentException e) { // no op - shouldnt happen. We check for static before calling // getInt(null) } catch (IllegalAccessException e) { // no op - shouldnt happen. We check for public before calling // getInt(null) } return getSystemColor(SWT.COLOR_BLACK); } /** * Get the SWT constant fields. * * @return the fields * @since 3.3 */ private static Field[] getFields() { if (cachedFields == null) { Class<SWT> clazz = SWT.class; Field[] allFields = clazz.getDeclaredFields(); ArrayList<Field> applicableFields = new ArrayList<>(allFields.length); for (int i = 0; i < allFields.length; i++) { Field field = allFields[i]; if (field.getType() == Integer.TYPE && Modifier.isStatic(field.getModifiers()) && Modifier.isPublic(field.getModifiers()) && Modifier.isFinal(field.getModifiers()) && field.getName().startsWith("COLOR")) { //$NON-NLS-1$ applicableFields.add(field); } } cachedFields = applicableFields.toArray(new Field[applicableFields.size()]); } return cachedFields; } /** * Blends the two color values according to the provided ratio. * * @param c1 * first color * @param c2 * second color * @param ratio * percentage of the first color in the blend (0-100) * @return the RGB value of the blended color * * @since 3.3 */ public static RGB blend(RGB c1, RGB c2, int ratio) { int r = blend(c1.red, c2.red, ratio); int g = blend(c1.green, c2.green, ratio); int b = blend(c1.blue, c2.blue, ratio); return new RGB(r, g, b); } private static int blend(int v1, int v2, int ratio) { int b = (ratio * v1 + (100 - ratio) * v2) / 100; return Math.min(255, b); } /** * Blend the two color values returning a value that is halfway between * them. * * @param val1 * the first value * @param val2 * the second value * @return the blended color */ public static RGB blend(RGB val1, RGB val2) { int red = blend(val1.red, val2.red); int green = blend(val1.green, val2.green); int blue = blend(val1.blue, val2.blue); return new RGB(red, green, blue); } /** * Blend the two color values returning a value that is halfway between * them. * * @param temp1 * the first value * @param temp2 * the second value * @return the blended int value */ private static int blend(int temp1, int temp2) { return (Math.abs(temp1 - temp2) / 2) + Math.min(temp1, temp2); } /** * Return the system color that matches the provided SWT constant value. * * @param colorId * the system color identifier * @return the RGB value of the supplied system color */ private static RGB getSystemColor(int colorId) { return Display.getCurrent().getSystemColor(colorId).getRGB(); } /** * Get the RGB value for a given color. * * @param rawValue * the raw value, either an RGB triple or an SWT constant name * @return the RGB value * @throws DataFormatException * thrown if the value cannot be interpreted as a color */ public static RGB getColorValue(String rawValue) throws DataFormatException { if (rawValue == null) { return null; } rawValue = rawValue.trim(); if (!isDirectValue(rawValue)) { return process(rawValue); } return StringConverter.asRGB(rawValue); } /** * Get the RGB values for a given color array. * * @param rawValues * the raw values, either RGB triple or an SWT constant * @return the RGB values */ public static RGB[] getColorValues(String[] rawValues) { RGB[] values = new RGB[rawValues.length]; for (int i = 0; i < rawValues.length; i++) { values[i] = getColorValue(rawValues[i]); } return values; } /** * Return whether the value returned by <code>getValue()</code> is already * in RGB form. * * @return whether the value returned by <code>getValue()</code> is * already in RGB form */ private static boolean isDirectValue(String rawValue) { return rawValue.indexOf(',') >= 0; } /** * Not intended to be instantiated. */ private ColorUtil() { // no-op } }