Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2018 IBM Corporation and others. * * This program and the accompanying materials * are made available under the terms of the Eclipse Public License 2.0 * which accompanies this distribution, and is available at * https://www.eclipse.org/legal/epl-2.0/ * * SPDX-License-Identifier: EPL-2.0 * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/ package org.eclipse.swt.graphics; import org.eclipse.swt.*; import org.eclipse.swt.internal.gtk.*; /** * Instances of this class manage the operating system resources that * implement SWT's RGB color model. To create a color you can either * specify the individual color components as integers in the range * 0 to 255 or provide an instance of an <code>RGB</code> or <code>RGBA</code>. * <p> * Application code must explicitly invoke the <code>Color.dispose()</code> * method to release the operating system resources managed by each instance * when those instances are no longer required. * </p> * * @see RGB * @see RGBA * @see Device#getSystemColor * @see <a href="http://www.eclipse.org/swt/snippets/#color">Color and RGB snippets</a> * @see <a href="http://www.eclipse.org/swt/examples.php">SWT Example: PaintExample</a> * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a> */ public final class Color extends Resource { /** * the handle to the OS color resource * (Warning: This field is platform dependent) * <p> * <b>IMPORTANT:</b> This field is <em>not</em> part of the SWT * public API. It is marked public only so that it can be shared * within the packages provided by SWT. It is not available on all * platforms and should never be accessed from application code. * </p> * * @noreference This field is not intended to be referenced by clients. */ public GdkRGBA handle; int alpha = 0; Color(Device device) { super(device); } /** * Constructs a new instance of this class given a device and the * desired red, green and blue values expressed as ints in the range * 0 to 255 (where 0 is black and 255 is full brightness). On limited * color devices, the color instance created by this call may not have * the same RGB values as the ones specified by the arguments. The * RGB values on the returned instance will be the color values of * the operating system color. * <p> * You must dispose the color when it is no longer required. * </p> * * @param device the device on which to allocate the color * @param red the amount of red in the color * @param green the amount of green in the color * @param blue the amount of blue in the color * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if device is null and there is no current device</li> * <li>ERROR_INVALID_ARGUMENT - if the red, green or blue argument is not between 0 and 255</li> * </ul> * * @see #dispose */ public Color(Device device, int red, int green, int blue) { super(device); init(red, green, blue, 255); init(); } /** * Constructs a new instance of this class given a device and the * desired red, green, blue & alpha values expressed as ints in the range * 0 to 255 (where 0 is black and 255 is full brightness). On limited * color devices, the color instance created by this call may not have * the same RGB values as the ones specified by the arguments. The * RGB values on the returned instance will be the color values of * the operating system color. * <p> * You must dispose the color when it is no longer required. * </p> * * @param device the device on which to allocate the color * @param red the amount of red in the color * @param green the amount of green in the color * @param blue the amount of blue in the color * @param alpha the amount of alpha in the color. Currently, SWT only honors extreme values for alpha i.e. 0 (transparent) or 255 (opaque). * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if device is null and there is no current device</li> * <li>ERROR_INVALID_ARGUMENT - if the red, green, blue or alpha argument is not between 0 and 255</li> * </ul> * * @see #dispose * @since 3.104 */ public Color(Device device, int red, int green, int blue, int alpha) { super(device); init(red, green, blue, alpha); init(); } /** * Constructs a new instance of this class given a device and an * <code>RGB</code> describing the desired red, green and blue values. * On limited color devices, the color instance created by this call * may not have the same RGB values as the ones specified by the * argument. The RGB values on the returned instance will be the color * values of the operating system color. * <p> * You must dispose the color when it is no longer required. * </p> * * @param device the device on which to allocate the color * @param rgb the RGB values of the desired color * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if device is null and there is no current device</li> * <li>ERROR_NULL_ARGUMENT - if the rgb argument is null</li> * <li>ERROR_INVALID_ARGUMENT - if the red, green or blue components of the argument are not between 0 and 255</li> * </ul> * * @see #dispose */ public Color(Device device, RGB rgb) { super(device); if (rgb == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); init(rgb.red, rgb.green, rgb.blue, 255); init(); } /** * Constructs a new instance of this class given a device and an * <code>RGBA</code> describing the desired red, green, blue & alpha values. * On limited color devices, the color instance created by this call * may not have the same RGBA values as the ones specified by the * argument. The RGBA values on the returned instance will be the color * values of the operating system color + alpha. * <p> * You must dispose the color when it is no longer required. * </p> * * @param device the device on which to allocate the color * @param rgba the RGBA values of the desired color. Currently, SWT only honors extreme values for alpha i.e. 0 (transparent) or 255 (opaque). * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if device is null and there is no current device</li> * <li>ERROR_NULL_ARGUMENT - if the rgba argument is null</li> * <li>ERROR_INVALID_ARGUMENT - if the red, green, blue or alpha components of the argument are not between 0 and 255</li> * </ul> * * @see #dispose * @since 3.104 */ public Color(Device device, RGBA rgba) { super(device); if (rgba == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); init(rgba.rgb.red, rgba.rgb.green, rgba.rgb.blue, rgba.alpha); init(); } /** * Constructs a new instance of this class given a device, an * <code>RGB</code> describing the desired red, green and blue values, * alpha specifying the level of transparency. * On limited color devices, the color instance created by this call * may not have the same RGB values as the ones specified by the * argument. The RGB values on the returned instance will be the color * values of the operating system color. * <p> * You must dispose the color when it is no longer required. * </p> * * @param device the device on which to allocate the color * @param rgb the RGB values of the desired color * @param alpha the alpha value of the desired color. Currently, SWT only honors extreme values for alpha i.e. 0 (transparent) or 255 (opaque). * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if device is null and there is no current device</li> * <li>ERROR_NULL_ARGUMENT - if the rgb argument is null</li> * <li>ERROR_INVALID_ARGUMENT - if the red, green, blue or alpha components of the argument are not between 0 and 255</li> * </ul> * * @see #dispose * @since 3.104 */ public Color(Device device, RGB rgb, int alpha) { super(device); if (rgb == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); init(rgb.red, rgb.green, rgb.blue, alpha); init(); } @Override void destroy() { handle = null; } /** * Compares the argument to the receiver, and returns true * if they represent the <em>same</em> object using a class * specific comparison. * * @param object the object to compare with this object * @return <code>true</code> if the object is the same as this object and <code>false</code> otherwise * * @see #hashCode */ @Override public boolean equals(Object object) { if (object == this) return true; if (!(object instanceof Color)) return false; Color color = (Color) object; GdkRGBA gdkRGBA = color.handle; if (handle == gdkRGBA) return true; if (this.getRed() != color.getRed()) return false; if (this.getGreen() != color.getGreen()) return false; if (this.getBlue() != color.getBlue()) return false; if (this.getAlpha() != color.getAlpha()) return false; return device == color.device; } /** * Returns the amount of alpha in the color, from 0 (transparent) to 255 (opaque). * * @return the alpha component of the color * * @exception SWTException <ul> * <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> * </ul> * @since 3.104 */ public int getAlpha() { if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED); return alpha; } /** * Returns the amount of blue in the color, from 0 to 255. * * @return the blue component of the color * * @exception SWTException <ul> * <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> * </ul> */ public int getBlue() { if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED); /* * Conversion formula comes from Cairo's _cairo_color_double_to_short() * and color_to_pixel() functions. See bug 549181 and 549101 for more info. */ int b = (((int) (handle.blue * 65535.0 + 0.5)) >> 8); return Math.min(b, 255); } /** * Returns the amount of green in the color, from 0 to 255. * * @return the green component of the color * * @exception SWTException <ul> * <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> * </ul> */ public int getGreen() { if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED); /* * Conversion formula comes from Cairo's _cairo_color_double_to_short() * and color_to_pixel() functions. See bug 549181 and 549101 for more info. */ int g = (((int) (handle.green * 65535.0 + 0.5)) >> 8); return Math.min(g, 255); } /** * Returns the amount of red in the color, from 0 to 255. * * @return the red component of the color * * @exception SWTException <ul> * <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> * </ul> */ public int getRed() { if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED); /* * Conversion formula comes from Cairo's _cairo_color_double_to_short() * and color_to_pixel() functions. See bug 549181 and 549101 for more info. */ int r = (((int) (handle.red * 65535.0 + 0.5)) >> 8); return Math.min(r, 255); } /** * Returns an integer hash code for the receiver. Any two * objects that return <code>true</code> when passed to * <code>equals</code> must return the same value for this * method. * * @return the receiver's hash * * @see #equals */ @Override public int hashCode() { if (isDisposed()) return 0; return (((this.getAlpha() * 31) + this.getGreen()) * 31 + this.getBlue()) * 31 + this.getRed(); } /** * Returns an <code>RGB</code> representing the receiver. * * @return the RGB for the color * * @exception SWTException <ul> * <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> * </ul> */ public RGB getRGB() { if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED); return new RGB(getRed(), getGreen(), getBlue()); } /** * Returns an <code>RGBA</code> representing the receiver. * * @return the RGBA for the color * * @exception SWTException <ul> * <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> * </ul> * @since 3.104 */ public RGBA getRGBA() { if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED); return new RGBA(getRed(), getGreen(), getBlue(), getAlpha()); } /** * Invokes platform specific functionality to allocate a new color. * <p> * <b>IMPORTANT:</b> This method is <em>not</em> part of the public * API for <code>Color</code>. It is marked public only so that it * can be shared within the packages provided by SWT. It is not * available on all platforms, and should never be called from * application code. * </p> * * @param device the device on which to allocate the color * @param gdkRGBA the handle for the color * * @noreference This method is not intended to be referenced by clients. */ public static Color gtk_new(Device device, GdkRGBA gdkRGBA) { Color color = new Color(device); color.handle = gdkRGBA; color.alpha = (int) (gdkRGBA.alpha * 255); return color; } /** * Invokes platform specific functionality to allocate a new color. * <p> * <b>IMPORTANT:</b> This method is <em>not</em> part of the public * API for <code>Color</code>. It is marked public only so that it * can be shared within the packages provided by SWT. It is not * available on all platforms, and should never be called from * application code. * </p> * * @param device the device on which to allocate the color * @param gdkRGBA the handle for the color * @param alpha the int for the alpha content in the color(Currently SWT honors extreme values for alpha ie. 0 or 255) * * @noreference This method is not intended to be referenced by clients. */ public static Color gtk_new(Device device, GdkRGBA gdkRGBA, int alpha) { Color color = new Color(device); color.handle = gdkRGBA; color.alpha = alpha; return color; } /** * Allocates the operating system resources associated * with the receiver. * * @param device the device on which to allocate the color * @param red the amount of red in the color * @param green the amount of green in the color * @param blue the amount of blue in the color * @param alpha the amount of alpha in the color * * @exception IllegalArgumentException <ul> * <li>ERROR_INVALID_ARGUMENT - if the red, green, blue or alpha argument is not between 0 and 255</li> * </ul> * * @see #dispose */ void init(int red, int green, int blue, int alpha) { if ((red > 255) || (red < 0) || (green > 255) || (green < 0) || (blue > 255) || (blue < 0) || (alpha > 255) || (alpha < 0)) { SWT.error(SWT.ERROR_INVALID_ARGUMENT); } GdkRGBA rgba = new GdkRGBA(); rgba.red = (double) red / 255; rgba.green = (double) green / 255; rgba.blue = (double) blue / 255; rgba.alpha = (double) alpha / 255; this.alpha = alpha; handle = rgba; } /** * Returns <code>true</code> if the color has been disposed, * and <code>false</code> otherwise. * <p> * This method gets the dispose state for the color. * When a color has been disposed, it is an error to * invoke any other method (except {@link #dispose()}) using the color. * * @return <code>true</code> when the color is disposed and <code>false</code> otherwise */ @Override public boolean isDisposed() { return handle == null; } /** * Returns a string containing a concise, human-readable * description of the receiver. * * @return a string representation of the receiver */ @Override public String toString() { if (isDisposed()) return "Color {*DISPOSED*}"; return "Color {" + getRed() + ", " + getGreen() + ", " + getBlue() + ", " + getAlpha() + "}"; } }