add support for plane-alpha in HWC
Change-Id: Ied228e689ca892c505fbd811fd2b8579287e4ac6
diff --git a/include/hardware/hwcomposer.h b/include/hardware/hwcomposer.h
index 391fe64..3b29f1f 100644
--- a/include/hardware/hwcomposer.h
+++ b/include/hardware/hwcomposer.h
@@ -202,13 +202,53 @@
* responsible for closing it when no longer needed.
*/
int releaseFenceFd;
+
+ /*
+ * Availability: HWC_DEVICE_API_VERSION_1_2
+ *
+ * Alpha value applied to the whole layer. The effective
+ * value of each pixel is computed as:
+ *
+ * if (blending == HWC_BLENDING_PREMULT)
+ * pixel.rgb = pixel.rgb * planeAlpha / 255
+ * pixel.a = pixel.a * planeAlpha / 255
+ *
+ * Then blending proceeds as usual according to the "blending"
+ * field above.
+ *
+ * NOTE: planeAlpha applies to YUV layers as well:
+ *
+ * pixel.rgb = yuv_to_rgb(pixel.yuv)
+ * if (blending == HWC_BLENDING_PREMULT)
+ * pixel.rgb = pixel.rgb * planeAlpha / 255
+ * pixel.a = planeAlpha
+ *
+ *
+ * IMPLEMENTATION NOTE:
+ *
+ * If the source image doesn't have an alpha channel, then
+ * the h/w can use the HWC_BLENDING_COVERAGE equations instead of
+ * HWC_BLENDING_PREMULT and simply set the alpha channel to
+ * planeAlpha.
+ *
+ * e.g.:
+ *
+ * if (blending == HWC_BLENDING_PREMULT)
+ * blending = HWC_BLENDING_COVERAGE;
+ * pixel.a = planeAlpha;
+ *
+ */
+ uint8_t planeAlpha;
+
+ /* reserved for future use */
+ uint8_t _pad[3];
};
};
/* Allow for expansion w/o breaking binary compatibility.
* Pad layer to 96 bytes, assuming 32-bit pointers.
*/
- int32_t reserved[24 - 18];
+ int32_t reserved[24 - 19];
} hwc_layer_1_t;