前言
图画混合形式
在之前的Paint的运用傍边咱们提到了高档烘托和滤镜，那么今天咱们来学习终究一个内容点Xfermode，咱们能经过运用Xfermode能够完结图画组合的作用
1.XFermode
在运用Paint的时分，咱们能经过运用Xfermode能够完结图画组合的作用将制作的图形的像素和Canvas上对应方位的像素依照必定的规矩进行混合，构成新的像素，再更新到Canvas中构成终究的图形，那图详细作用见下图
看到上述图形，其实这个时分咱们能够很明显的知道咱们的XFermode其实实际上便是在运用图形之间的相互组合以到达自己的想要的目的， 他供给了16种组合形式
ADD:饱满相加,对图画饱满度进行相加,不常用
CLEAR:清除图画
DARKEN:变暗,较深的色彩掩盖较浅的色彩，若两者深浅程度相同则混合
DST:只显现方针图画
DST_ATOP:在源图画和方针图画相交的当地制作【方针图画】，在不相交的当地制作【源图画】，相交处的作用遭到源图画和方针图画alpha的影响
DST_IN:只在源图画和方针图画相交的当地制作【方针图画】，制作作用遭到源图画对应当地透明度影响
DST_OUT:只在源图画和方针图画不相交的当地制作【方针图画】，在相交的当地依据源图画的alpha进行过滤，源图画彻底不透明则彻底过滤，彻底透明则不过滤
DST_OVER:将方针图画放在源图画上方
LIGHTEN:变亮，与DARKEN相反，DARKEN和LIGHTEN生成的图画成果与Android对色彩值深浅的界说有关
MULTIPLY:正片叠底，源图画素色彩值乘以方针图画素色彩值除以255得到混合后图画像素色彩值
OVERLAY:叠加
SCREEN:滤色，色彩均和,保存两个图层中较白的部分，较暗的部分被隐瞒
SRC:只显现源图画
SRC_ATOP:在源图画和方针图画相交的当地制作【源图画】，在不相交的当地制作【方针图画】，相交处的作用遭到源图画和方针图画alpha的影响
SRC_IN:只在源图画和方针图画相交的当地制作【源图画】
SRC_OUT:只在源图画和方针图画不相交的当地制作【源图画】，相交的当地依据方针图画的对应当地的alpha进行过滤，方针图画彻底不透明则彻底过滤，彻底透明则不过滤
SRC_OVER:将源图画放在方针图画上方
XOR:在源图画和方针图画相交的当地之外制作它们，在相交的当地遭到对应alpha和色值影响，假如彻底不透明则相交处彻底不制作
这个方法跟咱们上节课讲到的setColorFilter蛮相似的。 但是我门能够看到谷歌官方所供给的和咱们自己写的仍是有一些差异， 那么我门需求来了解到XFermode的本质究竟是什么，上面开篇咱们有提到过，XFermode是将制作的图形的像素和Canvas上对应方位的像素依照必定的规矩进行混合，那么咱们需求知道他究竟是怎么进行混合，怎么进行核算的 这个时分我门走到源码傍边，查看API文档发现其果然有三个子类：AvoidXfermode, PixelXorXfermode和PorterDuffXfermode这三个子类完结的功能要比setColorFilter的三个子类杂乱得多。 因为AvoidXfermode, PixelXorXfermode都现已被标示为过期了，所以这次主要研讨的是仍然在运用的PorterDuffXfermode
/**
* <p>Specialized implementation of {@link Paint}'s
* {@link Paint#setXfermode(Xfermode) transfer mode}. Refer to the
* documentation of the {@link PorterDuff.Mode} enum for more
* information on the available alpha compositing and blending modes.
*/
public class PorterDuffXfermode extends Xfermode {
/**
* Create an xfermode that uses the specified porter-duff mode.
*
* @param mode The porter-duff mode that is applied
*/
public PorterDuffXfermode(PorterDuff.Mode mode) {
porterDuffMode = mode.nativeInt;
}
}
那么在这儿咱们能够看到其实实际上这个类非常简略， 我门能够认为他便是一个常量类标示了16种形式， 而在这儿真正的形式实在mode傍边(下面大略看一下就行)
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="pretty print"
* 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;
}
}
}
这个时分咱们会发现比较的懵逼，都是html是什么情况？那么这个时分我帮大家做了个处理将这些注释贴到了一个html傍边(详细见课件)给大家翻译了一下
那么这儿经过翻译出来之后咱们能够很明显知道，这个类傍边所界说的是这些16种形式的常量以及16形式所能到达的作用，以及踏实怎么进行核算的。
那么这儿咱们就上面写的几个重点进行分析
The result (or output) alpha value is noted \(\alpha_{out}\). The result (or output)
color value is noted \(C_{out}\).
alpha的成果或许输出被标记为 \(\alpha_{out}\). 色彩值的成果或输出被标记为\(C_{out}\).
从这句话其实我门能够看出，他写的很明白 在上述的过程中有提到(\alpha_{out})表明透明输出值(C_{out}).表明是色彩输出值，那么其实便是经过两个图形核算的到这两个要害输出值便是构成咱们图形混合的最大隐秘 而下面便是详细的那些核算公式
/**
* <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);
咱们一个像素的色彩都是由四个重量组成，即ARGB，A表明的是咱们Alpha值，RGB表明的是色彩
S表明的是原像素，原像素的值表明[Sa,Sc] Sa表明的便是源像素的Alpha值，Sc表明源像素的色彩值 蓝色矩形表明的是原图片，黄色圆表明的是方针图片
在上述的核算公式傍边咱们关注几个要害点 alpha——透明度 C——色彩 src——原图 dst——方针图 out——输出
把这几个弄清楚，其实咱们的xfermode在我门面前就没有任何的隐秘可言了
那么留意， 这个是27版别的,与之前版别核算规矩上肯定有所差异， 其实咱们看版别的源码更好了解写，没有这么杂乱那么在此贴住以前老版别(21)的作为参考比对
public class PorterDuff {
// these value must match their native equivalents. See SkPorterDuff.h
public enum Mode {
/** [0, 0] */
CLEAR (0),
/** [Sa, Sc] */
SRC (1),
/** [Da, Dc] */
DST (2),
/** [Sa + (1 - Sa)*Da, Rc = Sc + (1 - Sa)*Dc] */
SRC_OVER (3),
/** [Sa + (1 - Sa)*Da, Rc = Dc + (1 - Da)*Sc] */
DST_OVER (4),
/** [Sa * Da, Sc * Da] */
SRC_IN (5),
/** [Sa * Da, Sa * Dc] */
DST_IN (6),
/** [Sa * (1 - Da), Sc * (1 - Da)] */
SRC_OUT (7),
/** [Da * (1 - Sa), Dc * (1 - Sa)] */
DST_OUT (8),
/** [Da, Sc * Da + (1 - Sa) * Dc] */
SRC_ATOP (9),
/** [Sa, Sa * Dc + Sc * (1 - Da)] */
DST_ATOP (10),
/** [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + (1 - Sa) * Dc] */
XOR (11),
/** [Sa + Da - Sa*Da,
Sc*(1 - Da) + Dc*(1 - Sa) + min(Sc, Dc)] */
DARKEN (12),
/** [Sa + Da - Sa*Da,
Sc*(1 - Da) + Dc*(1 - Sa) + max(Sc, Dc)] */
LIGHTEN (13),
/** [Sa * Da, Sc * Dc] */
MULTIPLY (14),
/** [Sa + Da - Sa * Da, Sc + Dc - Sc * Dc] */
SCREEN (15),
/** Saturate(S + D) */
ADD (16),
OVERLAY (17);
Mode(int nativeInt) {
this.nativeInt = nativeInt;
}
/**
* @hide
*/
public final int nativeInt;
}
}
二、混合形式分类
我门能够将混合形式分为三个类型（留意看形式常量的姓名）
1、SRC类
----优先显现的是源图片
SRC [Sa, Sc] —- 处理图片相交区域时，总是显现的是原图片
SRC_IN [Sa * Da, Sc * Da] —- 处理图片相交区域时，遭到方针图片的Alpha值影响 当咱们的方针图片为空白像素的时分，方针图片也会变成空白 简略的来说便是用方针图片的透明度来改动源图片的透明度和饱满度，当方针图片的透明度为0时，源图片就不会显现
SRC_OUT [Sa * (1 – Da), Sc * (1 – Da)] — 同SRC_IN相似 (1 – Da) 用咱们方针图片的透明度的补值来改动源图片的透明度和饱满度,当方针图片的透明度为不透明时，源图片就不会显现
SRC_ATOP [Da, Sc * Da + (1 – Sa) * Dc] —- 当透明度为100%和0%时，SRC_IN 和 SRC_ATOP是通用的 当透明度不为上述的两个值时，SRC_ATOP 比 SRC_IN 源图画的饱满度会增
2、DST类
----优先显现的是方针图片
DST_IN [Sa * Da, Sa * Dc] —– 对比一下SRC_IN，正好和咱们SRC_IN想法，在相交的时分以源图片的透明度来改动方针图片的透明度和饱满度 当源图片的透明度为0的时分，方针图片彻底不显现
3、其他的叠加作用
MULTIPLY[Sa * Da, Sc * Dc] —
运用：能够把图片的轮廓取出来
LIGHTEN -- 变亮
书架 头顶灯火变亮作用
那么到这儿咱们现已根本了解了XFermode的情况，咱们来看下详细是怎么运用的，从运用角度来讲soeasy, 只需求在Paint傍边调用一句代码( paint.setXfermode(Mode)就能完结 下面是官方给出的demo
public class sampleActivity extends AppCompatActivity {
// create a bitmap with a circle, used for the "dst" image
static Bitmap makeDst(int w, int h) {
Bitmap bm = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(bm);
Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);
p.setColor(0xFFFFCC44);
c.drawOval(new RectF(0, 0, w*3/4, h*3/4), p);
return bm;
}
// create a bitmap with a rect, used for the "src" image
static Bitmap makeSrc(int w, int h) {
Bitmap bm = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(bm);
Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);
p.setColor(0xFF66AAFF);
c.drawRect(w/3, h/3, w*19/20, h*19/20, p);
return bm;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new SampleView(this));
}
private static class SampleView extends View {
private static final int W = 200;
private static final int H = 200;
private static final int ROW_MAX = 4; // number of samples per row
private Bitmap mSrcB;
private Bitmap mDstB;
private Shader mBG; // background checker-board pattern
private static final Xfermode[] sModes = {
new PorterDuffXfermode(PorterDuff.Mode.CLEAR),
new PorterDuffXfermode(PorterDuff.Mode.SRC),
new PorterDuffXfermode(PorterDuff.Mode.DST),
new PorterDuffXfermode(PorterDuff.Mode.SRC_OVER),
new PorterDuffXfermode(PorterDuff.Mode.DST_OVER),
new PorterDuffXfermode(PorterDuff.Mode.SRC_IN),
new PorterDuffXfermode(PorterDuff.Mode.DST_IN),
new PorterDuffXfermode(PorterDuff.Mode.SRC_OUT),
new PorterDuffXfermode(PorterDuff.Mode.DST_OUT),
new PorterDuffXfermode(PorterDuff.Mode.SRC_ATOP),
new PorterDuffXfermode(PorterDuff.Mode.DST_ATOP),
new PorterDuffXfermode(PorterDuff.Mode.XOR),
new PorterDuffXfermode(PorterDuff.Mode.DARKEN),
new PorterDuffXfermode(PorterDuff.Mode.LIGHTEN),
new PorterDuffXfermode(PorterDuff.Mode.MULTIPLY),
new PorterDuffXfermode(PorterDuff.Mode.SCREEN)
};
private static final String[] sLabels = {
"Clear", "Src", "Dst", "SrcOver",
"DstOver", "SrcIn", "DstIn", "SrcOut",
"DstOut", "SrcATop", "DstATop", "Xor",
"Darken", "Lighten", "Multiply", "Screen"
};
public SampleView(Context context) {
super(context);
mSrcB = makeSrc(W, H);
mDstB = makeDst(W, H);
// make a ckeckerboard pattern
Bitmap bm = Bitmap.createBitmap(new int[] { 0xFFFFFFFF, 0xFFCCCCCC,
0xFFCCCCCC, 0xFFFFFFFF }, 2, 2,
Bitmap.Config.RGB_565);
mBG = new BitmapShader(bm,
Shader.TileMode.REPEAT,
Shader.TileMode.REPEAT);
Matrix m = new Matrix();
m.setScale(6, 6);
mBG.setLocalMatrix(m);
}
@Override protected void onDraw(Canvas canvas) {
canvas.drawColor(Color.WHITE);
Paint labelP = new Paint(Paint.ANTI_ALIAS_FLAG);
labelP.setTextAlign(Paint.Align.CENTER);
Paint paint = new Paint();
paint.setFilterBitmap(false);
canvas.translate(15, 35);
int x = 0;
int y = 0;
for (int i = 0; i < sModes.length; i++) {
// draw the border
paint.setStyle(Paint.Style.STROKE);
paint.setShader(null);
canvas.drawRect(x - 0.5f, y - 0.5f,
x + W + 0.5f, y + H + 0.5f, paint);
// draw the checker-board pattern
paint.setStyle(Paint.Style.FILL);
paint.setShader(mBG);
canvas.drawRect(x, y, x + W, y + H, paint);
// draw the src/dst example into our offscreen bitmap
int sc = canvas.saveLayer(x, y, x + W, y + H, null,
Canvas.MATRIX_SAVE_FLAG |
Canvas.CLIP_SAVE_FLAG |
Canvas.HAS_ALPHA_LAYER_SAVE_FLAG |
Canvas.FULL_COLOR_LAYER_SAVE_FLAG |
Canvas.CLIP_TO_LAYER_SAVE_FLAG);
canvas.translate(x, y);
canvas.drawBitmap(mDstB, 0, 0, paint);
paint.setXfermode(sModes[i]);
canvas.drawBitmap(mSrcB, 0, 0, paint);
paint.setXfermode(null);
canvas.restoreToCount(sc);
// draw the label
canvas.drawText(sLabels[i],
x + W/2, y - labelP.getTextSize()/2, labelP);
x += W + 10;
// wrap around when we've drawn enough for one row
if ((i % ROW_MAX) == ROW_MAX - 1) {
x = 0;
y += H + 30;
}
}
}
}
}
大家能够去试着运用一下
更多Android 知识点可参考
Android 性能调优系列
Android 车载学习指南
Android Framework核心知识点笔记
Android 八大知识体系
Android 中高档面试题锦
