Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2005 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 *******************************************************************************/ package org.eclipse.swt.graphics; import org.eclipse.swt.*; /** * Instances of this class describe the color data used by an image. * <p> * Depending on the depth of the image, the PaletteData can take one * of two forms, indicated by the isDirect field: * </p> * <dl> * <dt> * <em>isDirect is false</em> * </dt> * <dd> * If isDirect is <code>false</code>, this palette is an indexed * palette which maps pixel values to RGBs. The actual RGB values * may be retrieved by using the getRGBs() method. * </dd> * <dt> * <em>isDirect is true</em> * </dt> * <dd> * If isDirect is <code>true</code>, this palette is a direct color * palette. Instead of containing RGB values, it contains red, * green and blue mask and shift information which indicates how * the color components may be extracted from a given pixel. * This means that the RGB value is actually encoded in the pixel value. * <p> * In this case, the shift data is the number of bits required to shift * the RGB value to the left in order to align the high bit of the * corresponding mask with the high bit of the first byte. This number * may be negative, so care must be taken when shifting. For example, * with a red mask of 0xFF0000, the red shift would be -16. With a red * mask of 0x1F, the red shift would be 3. * </p> * </dd> * </dl> * * @see Image * @see RGB */ public final class PaletteData { /** * true if the receiver is a direct palette, * and false otherwise */ public boolean isDirect; /** * the RGB values for an indexed palette, where the * indices of the array correspond to pixel values */ public RGB[] colors; /** * the red mask for a direct palette */ public int redMask; /** * the green mask for a direct palette */ public int greenMask; /** * the blue mask for a direct palette */ public int blueMask; /** * the red shift for a direct palette */ public int redShift; /** * the green shift for a direct palette */ public int greenShift; /** * the blue shift for a direct palette */ public int blueShift; /** * Constructs a new indexed palette given an array of RGB values. * * @param colors the array of <code>RGB</code>s for the palette * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the argument is null</li> * </ul> */ public PaletteData(RGB[] colors) { if (colors == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); this.colors = colors; this.isDirect = false; } /** * Constructs a new direct palette given the red, green and blue masks. * * @param redMask the red mask * @param greenMask the green mask * @param blueMask the blue mask */ public PaletteData(int redMask, int greenMask, int blueMask) { this.redMask = redMask; this.greenMask = greenMask; this.blueMask = blueMask; this.isDirect = true; this.redShift = shiftForMask(redMask); this.greenShift = shiftForMask(greenMask); this.blueShift = shiftForMask(blueMask); } /** * Returns the pixel value corresponding to the given <code>RGB</code>. * * @param rgb the RGB to get the pixel value for * @return the pixel value for the given RGB * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the argument is null</li> * <li>ERROR_INVALID_ARGUMENT - if the RGB is not found in the palette</li> * </ul> */ public int getPixel(RGB rgb) { if (rgb == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); if (isDirect) { int pixel = 0; pixel |= (redShift < 0 ? rgb.red << -redShift : rgb.red >>> redShift) & redMask; pixel |= (greenShift < 0 ? rgb.green << -greenShift : rgb.green >>> greenShift) & greenMask; pixel |= (blueShift < 0 ? rgb.blue << -blueShift : rgb.blue >>> blueShift) & blueMask; return pixel; } else { for (int i = 0; i < colors.length; i++) { if (colors[i].equals(rgb)) return i; } /* The RGB did not exist in the palette */ SWT.error(SWT.ERROR_INVALID_ARGUMENT); return 0; } } /** * Returns an <code>RGB</code> corresponding to the given pixel value. * * @param pixel the pixel to get the RGB value for * @return the RGB value for the given pixel * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the argument is null</li> * <li>ERROR_INVALID_ARGUMENT - if the pixel does not exist in the palette</li> * </ul> */ public RGB getRGB(int pixel) { if (isDirect) { int r = pixel & redMask; r = (redShift < 0) ? r >>> -redShift : r << redShift; int g = pixel & greenMask; g = (greenShift < 0) ? g >>> -greenShift : g << greenShift; int b = pixel & blueMask; b = (blueShift < 0) ? b >>> -blueShift : b << blueShift; return new RGB(r, g, b); } else { if (pixel < 0 || pixel >= colors.length) { SWT.error(SWT.ERROR_INVALID_ARGUMENT); } return colors[pixel]; } } /** * Returns all the RGB values in the receiver if it is an * indexed palette, or null if it is a direct palette. * * @return the <code>RGB</code>s for the receiver or null */ public RGB[] getRGBs() { return colors; } /** * Computes the shift value for a given mask. * * @param mask the mask to compute the shift for * @return the shift amount * * @see PaletteData */ int shiftForMask(int mask) { for (int i = 31; i >= 0; i--) { if (((mask >> i) & 0x1) != 0) return 7 - i; } return 32; } }