1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16#pragma version(1)
17#pragma rs java_package_name(com.example.android.hdrviewfinder)
18#pragma rs_fp_relaxed
19
20rs_allocation gCurrentFrame;
21rs_allocation gPrevFrame;
22
23int gCutPointX = 0;
24int gDoMerge = 0;
25int gFrameCounter = 0;
26
27uchar4 __attribute__((kernel)) mergeHdrFrames(uchar4 prevPixel, uint32_t x, uint32_t y) {
28
29    // Read in pixel values from latest frame - YUV color space
30
31    uchar4 curPixel;
32    curPixel.r = rsGetElementAtYuv_uchar_Y(gCurrentFrame, x, y);
33    curPixel.g = rsGetElementAtYuv_uchar_U(gCurrentFrame, x, y);
34    curPixel.b = rsGetElementAtYuv_uchar_V(gCurrentFrame, x, y);
35    curPixel.a = 255;
36
37    uchar4 mergedPixel;
38    if (gDoMerge == 1) {
39        // Complex HDR fusion technique
40        mergedPixel = curPixel / 2 + prevPixel / 2;
41
42        /* Experimental color saturation boosting merge
43        mergedPixel.r = curPixel.r / 2 + prevPixel.r / 2;
44
45        uchar saturationCurrent = abs(curPixel.g - 128) + abs(curPixel.b - 128);
46        uchar saturationPrev = abs(prevPixel.g - 128) + abs(prevPixel.b - 128);
47        mergedPixel.g = saturationCurrent > saturationPrev ? curPixel.g : prevPixel.g;
48        mergedPixel.b = saturationCurrent > saturationPrev ? curPixel.b : prevPixel.b;
49        */
50    } else if (gCutPointX > 0) {
51        // Composite side by side
52        mergedPixel = ((x < gCutPointX) ^ (gFrameCounter & 0x1)) ?
53                curPixel : prevPixel;
54    } else {
55        // Straight passthrough
56        mergedPixel = curPixel;
57    }
58
59    // Convert YUV to RGB, JFIF transform with fixed-point math
60    // R = Y + 1.402 * (V - 128)
61    // G = Y - 0.34414 * (U - 128) - 0.71414 * (V - 128)
62    // B = Y + 1.772 * (U - 128)
63
64    int4 rgb;
65    rgb.r = mergedPixel.r +
66            mergedPixel.b * 1436 / 1024 - 179;
67    rgb.g = mergedPixel.r -
68            mergedPixel.g * 46549 / 131072 + 44 -
69            mergedPixel.b * 93604 / 131072 + 91;
70    rgb.b = mergedPixel.r +
71            mergedPixel.g * 1814 / 1024 - 227;
72    rgb.a = 255;
73
74    // Store current pixel for next frame
75    rsSetElementAt_uchar4(gPrevFrame, curPixel, x, y);
76
77    // Write out merged HDR result
78    uchar4 out = convert_uchar4(clamp(rgb, 0, 255));
79
80    return out;
81}
82