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HdrViewfinder / src / rs /

hdr_merge.rs

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/*
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 * Copyright (C) 2014 The Android Open Source Project
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 *      http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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#pragma version(1)
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#pragma rs java_package_name(com.example.android.hdrviewfinder)
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#pragma rs_fp_relaxed
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rs_allocation gCurrentFrame;
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rs_allocation gPrevFrame;
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int gCutPointX = 0;
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int gDoMerge = 0;
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int gFrameCounter = 0;
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uchar4 __attribute__((kernel)) mergeHdrFrames(uchar4 prevPixel, uint32_t x, uint32_t y) {
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    // Read in pixel values from latest frame - YUV color space
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    uchar4 curPixel;
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    curPixel.r = rsGetElementAtYuv_uchar_Y(gCurrentFrame, x, y);
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    curPixel.g = rsGetElementAtYuv_uchar_U(gCurrentFrame, x, y);
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    curPixel.b = rsGetElementAtYuv_uchar_V(gCurrentFrame, x, y);
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    curPixel.a = 255;
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    uchar4 mergedPixel;
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    if (gDoMerge == 1) {
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        // Complex HDR fusion technique
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        mergedPixel = curPixel / 2 + prevPixel / 2;
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        /* Experimental color saturation boosting merge
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        mergedPixel.r = curPixel.r / 2 + prevPixel.r / 2;
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        uchar saturationCurrent = abs(curPixel.g - 128) + abs(curPixel.b - 128);
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        uchar saturationPrev = abs(prevPixel.g - 128) + abs(prevPixel.b - 128);
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        mergedPixel.g = saturationCurrent > saturationPrev ? curPixel.g : prevPixel.g;
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        mergedPixel.b = saturationCurrent > saturationPrev ? curPixel.b : prevPixel.b;
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        */
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    } else if (gCutPointX > 0) {
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        // Composite side by side
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        mergedPixel = ((x < gCutPointX) ^ (gFrameCounter & 0x1)) ?
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                curPixel : prevPixel;
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    } else {
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        // Straight passthrough
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        mergedPixel = curPixel;
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    }
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    // Convert YUV to RGB, JFIF transform with fixed-point math
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    // R = Y + 1.402 * (V - 128)
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    // G = Y - 0.34414 * (U - 128) - 0.71414 * (V - 128)
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    // B = Y + 1.772 * (U - 128)
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    int4 rgb;
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    rgb.r = mergedPixel.r +
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            mergedPixel.b * 1436 / 1024 - 179;
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    rgb.g = mergedPixel.r -
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            mergedPixel.g * 46549 / 131072 + 44 -
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            mergedPixel.b * 93604 / 131072 + 91;
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    rgb.b = mergedPixel.r +
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            mergedPixel.g * 1814 / 1024 - 227;
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    rgb.a = 255;
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    // Store current pixel for next frame
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    rsSetElementAt_uchar4(gPrevFrame, curPixel, x, y);
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    // Write out merged HDR result
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    uchar4 out = convert_uchar4(clamp(rgb, 0, 255));
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    return out;
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}
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