xref: /frameworks/base/graphics/java/android/graphics/PorterDuff.java

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * 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 android.graphics;

/**
 * <p>This class contains the list of alpha compositing and blending modes
 * that can be passed to {@link PorterDuffXfermode}, a specialized implementation
 * of {@link Paint}'s {@link Paint#setXfermode(Xfermode) transfer mode}.
 * All the available modes can be found in the {@link Mode} enum.</p>
 */
public class PorterDuff {
    /**
     * {@usesMathJax}
     *
     * <h3>Porter-Duff</h3>
     *
     * <p>The name of the parent class is an homage to the work of Thomas Porter and
     * Tom Duff, presented in their seminal 1984 paper titled "Compositing Digital Images".
     * In this paper, the authors describe 12 compositing operators that govern how to
     * compute the color resulting of the composition of a source (the graphics object
     * to render) with a destination (the content of the render target).</p>
     *
     * <p>"Compositing Digital Images" was published in <em>Computer Graphics</em>
     * Volume 18, Number 3 dated July 1984.</p>
     *
     * <p>Because the work of Porter and Duff focuses solely on the effects of the alpha
     * channel of the source and destination, the 12 operators described in the original
     * paper are called alpha compositing modes here.</p>
     *
     * <p>For convenience, this class also provides several blending modes, which similarly
     * define the result of compositing a source and a destination but without being
     * constrained to the alpha channel. These blending modes are not defined by Porter
     * and Duff but have been included in this class for convenience purposes.</p>
     *
     * <h3>Diagrams</h3>
     *
     * <p>All the example diagrams presented below use the same source and destination
     * images:</p>
     *
     * <table summary="Source and Destination" style="background-color: transparent;">
     *     <tr>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_SRC.png" />
     *             <figcaption>Source image</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_DST.png" />
     *             <figcaption>Destination image</figcaption>
     *         </td>
     *     </tr>
     * </table>
     *
     * <p>The order of drawing operations used to generate each diagram is shown in the
     * following code snippet:</p>
     *
     * <pre class="prettyprint">
     * Paint paint = new Paint();
     * canvas.drawBitmap(destinationImage, 0, 0, paint);
     *
     * PorterDuff.Mode mode = // choose a mode
     * paint.setXfermode(new PorterDuffXfermode(mode));
     *
     * canvas.drawBitmap(sourceImage, 0, 0, paint);
     * </pre>

     *
     * <h3>Alpha compositing modes</h3>
     *
     * <table summary="Alpha compositing modes" style="background-color: transparent;">
     *     <tr>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_SRC.png" />
     *             <figcaption>{@link #SRC Source}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_SRC_OVER.png" />
     *             <figcaption>{@link #SRC_OVER Source Over}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_SRC_IN.png" />
     *             <figcaption>{@link #SRC_IN Source In}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_SRC_ATOP.png" />
     *             <figcaption>{@link #SRC_ATOP Source Atop}</figcaption>
     *         </td>
     *     </tr>
     *     <tr>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_DST.png" />
     *             <figcaption>{@link #DST Destination}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_DST_OVER.png" />
     *             <figcaption>{@link #DST_OVER Destination Over}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_DST_IN.png" />
     *             <figcaption>{@link #DST_IN Destination In}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_DST_ATOP.png" />
     *             <figcaption>{@link #DST_ATOP Destination Atop}</figcaption>
     *         </td>
     *     </tr>
     *     <tr>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_CLEAR.png" />
     *             <figcaption>{@link #CLEAR Clear}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_SRC_OUT.png" />
     *             <figcaption>{@link #SRC_OUT Source Out}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_DST_OUT.png" />
     *             <figcaption>{@link #DST_OUT Destination Out}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_XOR.png" />
     *             <figcaption>{@link #XOR Exclusive Or}</figcaption>
     *         </td>
     *     </tr>
     * </table>
     *
     * <h3>Blending modes</h3>
     *
     * <table summary="Blending modes" style="background-color: transparent;">
     *     <tr>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_DARKEN.png" />
     *             <figcaption>{@link #DARKEN Darken}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_LIGHTEN.png" />
     *             <figcaption>{@link #LIGHTEN Lighten}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_MULTIPLY.png" />
     *             <figcaption>{@link #MULTIPLY Multiply}</figcaption>
     *         </td>
     *     </tr>
     *     <tr>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_SCREEN.png" />
     *             <figcaption>{@link #SCREEN Screen}</figcaption>
     *         </td>
     *         <td style="border: none; text-align: center;">
     *             <img src="{@docRoot}reference/android/images/graphics/composite_OVERLAY.png" />
     *             <figcaption>{@link #OVERLAY Overlay}</figcaption>
     *         </td>
     *     </tr>
     * </table>
     *
     * <h3>Compositing equations</h3>
     *
     * <p>The documentation of each individual alpha compositing or blending mode below
     * provides the exact equation used to compute alpha and color value of the result
     * of the composition of a source and destination.</p>
     *
     * <p>The result (or output) alpha value is noted \(\alpha_{out}\). The result (or output)
     * color value is noted \(C_{out}\).</p>
     */
    public enum Mode {
        // these value must match their native equivalents. See SkXfermode.h
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_CLEAR.png" />
         *     <figcaption>Destination pixels covered by the source are cleared to 0.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = 0\)</p>
         * <p>\(C_{out} = 0\)</p>
         */
        CLEAR       (0),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_SRC.png" />
         *     <figcaption>The source pixels replace the destination pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{src}\)</p>
         * <p>\(C_{out} = C_{src}\)</p>
         */
        SRC         (1),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_DST.png" />
         *     <figcaption>The source pixels are discarded, leaving the destination intact.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{dst}\)</p>
         * <p>\(C_{out} = C_{dst}\)</p>
         */
        DST         (2),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_SRC_OVER.png" />
         *     <figcaption>The source pixels are drawn over the destination pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{src} + (1 - \alpha_{src}) * \alpha_{dst}\)</p>
         * <p>\(C_{out} = C_{src} + (1 - \alpha_{src}) * C_{dst}\)</p>
         */
        SRC_OVER    (3),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_DST_OVER.png" />
         *     <figcaption>The source pixels are drawn behind the destination pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{dst} + (1 - \alpha_{dst}) * \alpha_{src}\)</p>
         * <p>\(C_{out} = C_{dst} + (1 - \alpha_{dst}) * C_{src}\)</p>
         */
        DST_OVER    (4),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_SRC_IN.png" />
         *     <figcaption>Keeps the source pixels that cover the destination pixels,
         *     discards the remaining source and destination pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{src} * \alpha_{dst}\)</p>
         * <p>\(C_{out} = C_{src} * \alpha_{dst}\)</p>
         */
        SRC_IN      (5),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_DST_IN.png" />
         *     <figcaption>Keeps the destination pixels that cover source pixels,
         *     discards the remaining source and destination pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{src} * \alpha_{dst}\)</p>
         * <p>\(C_{out} = C_{dst} * \alpha_{src}\)</p>
         */
        DST_IN      (6),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_SRC_OUT.png" />
         *     <figcaption>Keeps the source pixels that do not cover destination pixels.
         *     Discards source pixels that cover destination pixels. Discards all
         *     destination pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = (1 - \alpha_{dst}) * \alpha_{src}\)</p>
         * <p>\(C_{out} = (1 - \alpha_{dst}) * C_{src}\)</p>
         */
        SRC_OUT     (7),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_DST_OUT.png" />
         *     <figcaption>Keeps the destination pixels that are not covered by source pixels.
         *     Discards destination pixels that are covered by source pixels. Discards all
         *     source pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = (1 - \alpha_{src}) * \alpha_{dst}\)</p>
         * <p>\(C_{out} = (1 - \alpha_{src}) * C_{dst}\)</p>
         */
        DST_OUT     (8),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_SRC_ATOP.png" />
         *     <figcaption>Discards the source pixels that do not cover destination pixels.
         *     Draws remaining source pixels over destination pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{dst}\)</p>
         * <p>\(C_{out} = \alpha_{dst} * C_{src} + (1 - \alpha_{src}) * C_{dst}\)</p>
         */
        SRC_ATOP    (9),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_DST_ATOP.png" />
         *     <figcaption>Discards the destination pixels that are not covered by source pixels.
         *     Draws remaining destination pixels over source pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{src}\)</p>
         * <p>\(C_{out} = \alpha_{src} * C_{dst} + (1 - \alpha_{dst}) * C_{src}\)</p>
         */
        DST_ATOP    (10),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_XOR.png" />
         *     <figcaption>Discards the source and destination pixels where source pixels
         *     cover destination pixels. Draws remaining source pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = (1 - \alpha_{dst}) * \alpha_{src} + (1 - \alpha_{src}) * \alpha_{dst}\)</p>
         * <p>\(C_{out} = (1 - \alpha_{dst}) * C_{src} + (1 - \alpha_{src}) * C_{dst}\)</p>
         */
        XOR         (11),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_DARKEN.png" />
         *     <figcaption>Retains the smallest component of the source and
         *     destination pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{src} + \alpha_{dst} - \alpha_{src} * \alpha_{dst}\)</p>
         * <p>\(C_{out} = (1 - \alpha_{dst}) * C_{src} + (1 - \alpha_{src}) * C_{dst} + min(C_{src}, C_{dst})\)</p>
         */
        DARKEN      (16),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_LIGHTEN.png" />
         *     <figcaption>Retains the largest component of the source and
         *     destination pixel.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{src} + \alpha_{dst} - \alpha_{src} * \alpha_{dst}\)</p>
         * <p>\(C_{out} = (1 - \alpha_{dst}) * C_{src} + (1 - \alpha_{src}) * C_{dst} + max(C_{src}, C_{dst})\)</p>
         */
        LIGHTEN     (17),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_MULTIPLY.png" />
         *     <figcaption>Multiplies the source and destination pixels.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{src} * \alpha_{dst}\)</p>
         * <p>\(C_{out} = C_{src} * C_{dst}\)</p>
         */
        MULTIPLY    (13),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_SCREEN.png" />
         *     <figcaption>Adds the source and destination pixels, then subtracts the
         *     source pixels multiplied by the destination.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{src} + \alpha_{dst} - \alpha_{src} * \alpha_{dst}\)</p>
         * <p>\(C_{out} = C_{src} + C_{dst} - C_{src} * C_{dst}\)</p>
         */
        SCREEN      (14),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_ADD.png" />
         *     <figcaption>Adds the source pixels to the destination pixels and saturates
         *     the result.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = max(0, min(\alpha_{src} + \alpha_{dst}, 1))\)</p>
         * <p>\(C_{out} = max(0, min(C_{src} + C_{dst}, 1))\)</p>
         */
        ADD         (12),
        /**
         * <p>
         *     <img src="{@docRoot}reference/android/images/graphics/composite_OVERLAY.png" />
         *     <figcaption>Multiplies or screens the source and destination depending on the
         *     destination color.</figcaption>
         * </p>
         * <p>\(\alpha_{out} = \alpha_{src} + \alpha_{dst} - \alpha_{src} * \alpha_{dst}\)</p>
         * <p>\(\begin{equation}
         * C_{out} = \begin{cases} 2 * C_{src} * C_{dst} & 2 * C_{dst} \lt \alpha_{dst} \\
         * \alpha_{src} * \alpha_{dst} - 2 (\alpha_{dst} - C_{src}) (\alpha_{src} - C_{dst}) & otherwise \end{cases}
         * \end{equation}\)</p>
         */
        OVERLAY     (15);

        Mode(int nativeInt) {
            this.nativeInt = nativeInt;
        }

        /**
         * @hide
         */
        public final int nativeInt;
    }

    /**
     * @hide
     */
    public static int modeToInt(Mode mode) {
        return mode.nativeInt;
    }

    /**
     * @hide
     */
    public static Mode intToMode(int val) {
        switch (val) {
            default:
            case  0: return Mode.CLEAR;
            case  1: return Mode.SRC;
            case  2: return Mode.DST;
            case  3: return Mode.SRC_OVER;
            case  4: return Mode.DST_OVER;
            case  5: return Mode.SRC_IN;
            case  6: return Mode.DST_IN;
            case  7: return Mode.SRC_OUT;
            case  8: return Mode.DST_OUT;
            case  9: return Mode.SRC_ATOP;
            case 10: return Mode.DST_ATOP;
            case 11: return Mode.XOR;
            case 16: return Mode.DARKEN;
            case 17: return Mode.LIGHTEN;
            case 13: return Mode.MULTIPLY;
            case 14: return Mode.SCREEN;
            case 12: return Mode.ADD;
            case 15: return Mode.OVERLAY;
        }
    }
}