* 
* 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.
*/ public class PorterDuff { /** * {@usesMathJax} * *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).
* *"Compositing Digital Images" was published in Computer Graphics * Volume 18, Number 3 dated July 1984.
* *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.
* *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.
* *All the example diagrams presented below use the same source and destination * images:
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The order of drawing operations used to generate each diagram is shown in the * following code snippet:
* *
* 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);
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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.
* *The result (or output) alpha value is noted \(\alpha_{out}\). The result (or output) * color value is noted \(C_{out}\).
*/ public enum Mode { // these value must match their native equivalents. See SkXfermode.h /** *
*
*
\(\alpha_{out} = 0\)
*\(C_{out} = 0\)
*/ CLEAR (0), /** *
*
*
\(\alpha_{out} = \alpha_{src}\)
*\(C_{out} = C_{src}\)
*/ SRC (1), /** *
*
*
\(\alpha_{out} = \alpha_{dst}\)
*\(C_{out} = C_{dst}\)
*/ DST (2), /** *
*
*
\(\alpha_{out} = \alpha_{src} + (1 - \alpha_{src}) * \alpha_{dst}\)
*\(C_{out} = C_{src} + (1 - \alpha_{src}) * C_{dst}\)
*/ SRC_OVER (3), /** *
*
*
\(\alpha_{out} = \alpha_{dst} + (1 - \alpha_{dst}) * \alpha_{src}\)
*\(C_{out} = C_{dst} + (1 - \alpha_{dst}) * C_{src}\)
*/ DST_OVER (4), /** *
*
*
\(\alpha_{out} = \alpha_{src} * \alpha_{dst}\)
*\(C_{out} = C_{src} * \alpha_{dst}\)
*/ SRC_IN (5), /** *
*
*
\(\alpha_{out} = \alpha_{src} * \alpha_{dst}\)
*\(C_{out} = C_{dst} * \alpha_{src}\)
*/ DST_IN (6), /** *
*
*
\(\alpha_{out} = (1 - \alpha_{dst}) * \alpha_{src}\)
*\(C_{out} = (1 - \alpha_{dst}) * C_{src}\)
*/ SRC_OUT (7), /** *
*
*
\(\alpha_{out} = (1 - \alpha_{src}) * \alpha_{dst}\)
*\(C_{out} = (1 - \alpha_{src}) * C_{dst}\)
*/ DST_OUT (8), /** *
*
*
\(\alpha_{out} = \alpha_{dst}\)
*\(C_{out} = \alpha_{dst} * C_{src} + (1 - \alpha_{src}) * C_{dst}\)
*/ SRC_ATOP (9), /** *
*
*
\(\alpha_{out} = \alpha_{src}\)
*\(C_{out} = \alpha_{src} * C_{dst} + (1 - \alpha_{dst}) * C_{src}\)
*/ DST_ATOP (10), /** *
*
*
\(\alpha_{out} = (1 - \alpha_{dst}) * \alpha_{src} + (1 - \alpha_{src}) * \alpha_{dst}\)
*\(C_{out} = (1 - \alpha_{dst}) * C_{src} + (1 - \alpha_{src}) * C_{dst}\)
*/ XOR (11), /** *
*
*
\(\alpha_{out} = \alpha_{src} + \alpha_{dst} - \alpha_{src} * \alpha_{dst}\)
*\(C_{out} = (1 - \alpha_{dst}) * C_{src} + (1 - \alpha_{src}) * C_{dst} + min(C_{src}, C_{dst})\)
*/ DARKEN (16), /** *
*
*
\(\alpha_{out} = \alpha_{src} + \alpha_{dst} - \alpha_{src} * \alpha_{dst}\)
*\(C_{out} = (1 - \alpha_{dst}) * C_{src} + (1 - \alpha_{src}) * C_{dst} + max(C_{src}, C_{dst})\)
*/ LIGHTEN (17), /** *
*
*
\(\alpha_{out} = \alpha_{src} * \alpha_{dst}\)
*\(C_{out} = C_{src} * C_{dst}\)
*/ MULTIPLY (13), /** *
*
*
\(\alpha_{out} = \alpha_{src} + \alpha_{dst} - \alpha_{src} * \alpha_{dst}\)
*\(C_{out} = C_{src} + C_{dst} - C_{src} * C_{dst}\)
*/ SCREEN (14), /** *
* 
*
\(\alpha_{out} = max(0, min(\alpha_{src} + \alpha_{dst}, 1))\)
*\(C_{out} = max(0, min(C_{src} + C_{dst}, 1))\)
*/ ADD (12), /** *
*
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\(\alpha_{out} = \alpha_{src} + \alpha_{dst} - \alpha_{src} * \alpha_{dst}\)
*\(\begin{equation} * C_{out} = \begin{cases} 2 * C_{src} * C_{dst} & 2 * C_{dst} \lt \alpha_{dst} \\ * \alpha_{src} * \alpha_{dst} - 2 (\alpha_{dst} - C_{src}) (\alpha_{src} - C_{dst}) & otherwise \end{cases} * \end{equation}\)
*/ 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; } } }