Android Renderscript - Rotate YUV data in Renderscript

Question

Based on the discussion I had at Camera2 api Imageformat.yuv_420_888 results on rotated image, I wanted to know how to adjust the lookup done via rsGetElementAt_uchar methods so that the YUV data is rotated by 90 degree. I also have a project like the HdrViewfinder provided by Google. The problem is that the output is in landscape because the output surface used as target surface is connected to the yuv allocation which does not care if the device is in landscape or portrait mode. But I want to adjust the code so that it is in portrait mode. Therefore, I took a custom YUVToRGBA renderscript but I do not know what to change to rotate the output. Can somebody help me to adjust the following custom YUVtoRGBA script by 90 degree because I want to use the output in portrait mode:

// Needed directive for RS to work
#pragma version(1)

// The java_package_name directive needs to use your Activity's package path
#pragma rs java_package_name(net.hydex11.cameracaptureexample)

rs_allocation inputAllocation;

int wIn, hIn;
int numTotalPixels;

// Function to invoke before applying conversion
void setInputImageSize(int _w, int _h)
{
    wIn = _w;
    hIn = _h;
    numTotalPixels = wIn * hIn;
}

// Kernel that converts a YUV element to a RGBA one
uchar4 __attribute__((kernel)) convert(uint32_t x, uint32_t y)
{

    // YUV 4:2:0 planar image, with 8 bit Y samples, followed by
    // interleaved V/U plane with 8bit 2x2 subsampled chroma samples
    int baseIdx = x + y * wIn;
    int baseUYIndex = numTotalPixels + (y >> 1) * wIn + (x & 0xfffffe);

    uchar _y = rsGetElementAt_uchar(inputAllocation, baseIdx);
    uchar _u = rsGetElementAt_uchar(inputAllocation, baseUYIndex);
    uchar _v = rsGetElementAt_uchar(inputAllocation, baseUYIndex + 1);
    _y = _y < 16 ? 16 : _y;

    short Y = ((short)_y) - 16;
    short U = ((short)_u) - 128;
    short V = ((short)_v) - 128;

    uchar4 out;
    out.r = (uchar) clamp((float)(
        (Y * 298 + V * 409 + 128) >> 8), 0.f, 255.f);   
    out.g = (uchar) clamp((float)(
        (Y * 298 - U * 100 - V * 208 + 128) >> 8), 0.f, 255.f); 
    out.b = (uchar) clamp((float)(
        (Y * 298 + U * 516 + 128) >> 8), 0.f, 255.f); // 
    out.a = 255;

    return out;
}

I have found that custom script at https://bitbucket.org/cmaster11/rsbookexamples/src/tip/CameraCaptureExample/app/src/main/rs/customYUVToRGBAConverter.fs .

Here someone has put the Java code to rotate YUV data. But I want to do it in Renderscript since that is faster.

Any help would be great.

best regards,

Answer 1

I'm assuming you want the output to be in RGBA, as in your conversion script. You should be able to use an approach like that used in this answer; that is, simply modify the x and y coordinates as the first step in the convert kernel:

//Rotate 90 deg clockwise during the conversion
uchar4 __attribute__((kernel)) convert(uint32_t inX, uint32_t inY)
{
    uint32_t x = wIn - 1 - inY;
    uint32_t y = inX;

    //...rest of the function

Note the changes to the parameter names.

This presumes you have set up the output dimensions correctly (see linked answer). A 270 degree rotation can be accomplished in a similar way.