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Commit 96624731 authored by Nipun Kwatra's avatar Nipun Kwatra
Browse files

Added downsample() 

Added a downsample function which downsamples the source image
starting at an offset and skipping every few pixels. Currently
no low pass filtering is done, but it should be added later.

Change-Id: Iec34092c536bfc661a15521e6a1ef2ef3f815c61
parent d1fbdf1a

include/media/stagefright/YUVCanvas.h

+12 −0
Original line number Diff line number Diff line
@@ -55,6 +55,18 @@ public: 
            int32_t destStartX, int32_t destStartY,

            const YUVImage &srcImage);



    // Downsamples the srcImage into the canvas' target image (mYUVImage)

    // The downsampling copies pixels from the source image starting at

    // (srcOffsetX, srcOffsetY) to the target image, starting at (0, 0).

    // For each X increment in the target image, skipX pixels are skipped

    // in the source image.

    // Similarly for each Y increment in the target image, skipY pixels

    // are skipped in the source image.

    void downsample(

            int32_t srcOffsetX, int32_t srcOffsetY,

            int32_t skipX, int32_t skipY,

            const YUVImage &srcImage);



private:

    YUVImage& mYUVImage;

media/libstagefright/yuv/YUVCanvas.cpp

+29 −1
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#define LOG_NDEBUG 0

#define LOG_TAG "YUVCanvas"



#include <media/stagefright/MediaDebug.h>

#include <media/stagefright/YUVCanvas.h>

#include <media/stagefright/YUVImage.h>

#include <ui/Rect.h>
@@ -80,4 +81,31 @@ void YUVCanvas::CopyImageRect( 
    }

}



void YUVCanvas::downsample(

        int32_t srcOffsetX, int32_t srcOffsetY,

        int32_t skipX, int32_t skipY,

        const YUVImage &srcImage) {

    // TODO: Add a low pass filter for downsampling.



    // Check that srcImage is big enough to fill mYUVImage.

    CHECK((srcOffsetX + (mYUVImage.width() - 1) * skipX) < srcImage.width());

    CHECK((srcOffsetY + (mYUVImage.height() - 1) * skipY) < srcImage.height());



    uint8_t yValue;

    uint8_t uValue;

    uint8_t vValue;



    int32_t srcY = srcOffsetY;

    for (int32_t y = 0; y < mYUVImage.height(); ++y) {

        int32_t srcX = srcOffsetX;

        for (int32_t x = 0; x < mYUVImage.width(); ++x) {

            srcImage.getPixelValue(srcX, srcY, &yValue, &uValue, &vValue);

            mYUVImage.setPixelValue(x, y, yValue, uValue, vValue);



            srcX += skipX;

        }

        srcY += skipY;

    }

}



}  // namespace android