Java tutorial
/* * Copyright 2010 Google Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); you may not * use this file except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations under * the License. */ package com.google.gwt.canvas.dom.client; import com.google.gwt.core.client.JavaScriptObject; /** * Object that holds image data and a size. * * @see <a href="http://www.w3.org/TR/2dcontext/#imagedata">HTML Canvas 2D * ImageData</a> */ public class ImageData extends JavaScriptObject { /** * Number of colors at each location in the array. * * Because image data is stored as RGBA, this is 4. */ private static final int NUM_COLORS = 4; /** * Offsets for each color use RGBA ordering. */ private static final int OFFSET_RED = 0; private static final int OFFSET_GREEN = 1; private static final int OFFSET_BLUE = 2; private static final int OFFSET_ALPHA = 3; protected ImageData() { } /** * Returns the alpha value at position (x,y). * * @param x the x coordinate * @param y the y coordinate * @return the alpha value at position (x,y), or 0 if not in the image * @see #setAlphaAt(int, int, int) * @see #getColorAt(int, int, int) */ public final int getAlphaAt(int x, int y) { return getColorAt(x, y, OFFSET_ALPHA); } /** * Returns the blue value at position (x,y). * * @param x the x coordinate * @param y the y coordinate * @return the blue value at position (x,y), or 0 if not in the image * @see #setBlueAt(int, int, int) * @see #getColorAt(int, int, int) */ public final int getBlueAt(int x, int y) { return getColorAt(x, y, OFFSET_BLUE); } /** * Returns a canvas pixel array of size width * height * 4. * * @return a {@link CanvasPixelArray} object */ public final native CanvasPixelArray getData() /*-{ return this.data; }-*/; /** * Returns the green value at position (x,y). * * @param x the x coordinate * @param y the y coordinate * @return the green value at position (x,y), or 0 if not in the image * @see #setGreenAt(int, int, int) * @see #getColorAt(int, int, int) */ public final int getGreenAt(int x, int y) { return getColorAt(x, y, OFFSET_GREEN); } /** * Returns the height of this image data object. * * @return the image height as an int */ public final native int getHeight() /*-{ return this.height; }-*/; /** * Returns the red value at position (x,y). * * @param x the x coordinate * @param y the y coordinate * @return the red value at position (x,y), or 0 if not in the image * @see #setRedAt(int, int, int) * @see #getColorAt(int, int, int) */ public final int getRedAt(int x, int y) { return getColorAt(x, y, OFFSET_RED); } /** * Returns the width of this image data object. * * @return the image width as an int */ public final native int getWidth() /*-{ return this.width; }-*/; /** * Sets the alpha value at position (x,y). * * @param alpha the alpha value * @param x the x coordinate * @param y the y coordinate * @see #getAlphaAt(int, int) * @see #getColorAt(int, int, int) */ public final void setAlphaAt(int alpha, int x, int y) { setColorAt(alpha, x, y, OFFSET_ALPHA); } /** * Sets the blue value at position (x,y). * * @param blue the blue value * @param x the x coordinate * @param y the y coordinate * @see #getBlueAt(int, int) * @see #getColorAt(int, int, int) */ public final void setBlueAt(int blue, int x, int y) { setColorAt(blue, x, y, OFFSET_BLUE); } /** * Sets the green value at position (x,y). * * @param green the green value * @param x the x coordinate * @param y the y coordinate * @see #getGreenAt(int, int) * @see #getColorAt(int, int, int) */ public final void setGreenAt(int green, int x, int y) { setColorAt(green, x, y, OFFSET_GREEN); } /** * Sets the red value at position (x,y). * * @param red the red value * @param x the x coordinate * @param y the y coordinate * @see #getRedAt(int, int) * @see #getColorAt(int, int, int) */ public final void setRedAt(int red, int x, int y) { setColorAt(red, x, y, OFFSET_RED); } /** * Returns the color value at position (x,y) with the specified offset. * * Colors are stored in RGBA format, where the offset determines the color * channel (R, G, B, or A). The values are stored in row-major order. If the * specified location is not in the image, 0 is returned. * * @param x the x coordinate * @param y the y coordinate * @param offset the color offset * @return the color value at position (x,y), or 0 if not in the image * @see #setColorAt(int, int, int, int) */ private native int getColorAt(int x, int y, int offset) /*-{ return this.data[@com.google.gwt.canvas.dom.client.ImageData::NUM_COLORS * (x + y * this.width) + offset] || 0; }-*/; /** * Sets the color value at position (x,y) with the specified offset. * * Colors are stored in RGBA format, where the offset determines the color * (R, G, B, or A.) The values are stored in row-major order. * * @param color the color (in the range 0...255) * @param x the x coordinate * @param y the y coordinate * @param offset the color offset * @see #getColorAt(int, int, int) */ private native void setColorAt(int color, int x, int y, int offset) /*-{ this.data[@com.google.gwt.canvas.dom.client.ImageData::NUM_COLORS * (x + y * this.width) + offset] = color; }-*/; }