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      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 
     20 rs_allocation gCurrentFrame;
     21 rs_allocation gPrevFrame;
     22 
     23 int gCutPointX = 0;
     24 int gDoMerge = 0;
     25 int gFrameCounter = 0;
     26 
     27 uchar4 __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