Android camera2下YUV_420_888图像转换为位图错误

Question

我试图将YUV_420_888图像转换为位图，来自camera2预览。但是输出图像的颜色不正确。

请让我知道如果有人能发现转换的问题：

@Override
public void onImageAvailable(ImageReader reader)
{
    RenderScript rs = RenderScript.create(this.mContext);

    final Image image = reader.acquireLatestImage();

    final Image.Plane[] planes = image.getPlanes();
    final ByteBuffer planeY = planes[0].getBuffer();
    final ByteBuffer planeU = planes[1].getBuffer();
    final ByteBuffer planeV = planes[2].getBuffer();

    // Get the YUV planes data

    final int Yb = planeY.rewind().remaining();
    final int Ub = planeU.rewind().remaining();
    final int Vb = planeV.rewind().remaining();

    final ByteBuffer yuvData = ByteBuffer.allocateDirect(Yb + Ub + Vb);

    planeY.get(yuvData.array(), 0, Yb);
    planeU.get(yuvData.array(), Yb, Vb);
    planeV.get(yuvData.array(), Yb + Vb, Ub);

    // Initialize Renderscript

    Type.Builder yuvType = new Type.Builder(rs, Element.YUV(rs))
            .setX(image.getWidth())
            .setY(image.getHeight())
            .setYuvFormat(ImageFormat.YUV_420_888);

    final Type.Builder rgbaType = new Type.Builder(rs, Element.RGBA_8888(rs))
            .setX(image.getWidth())
            .setY(image.getHeight());

    Allocation yuvAllocation = Allocation.createTyped(rs, yuvType.create(), Allocation.USAGE_SCRIPT);
    Allocation rgbAllocation = Allocation.createTyped(rs, rgbaType.create(), Allocation.USAGE_SCRIPT);

    // Convert

    yuvAllocation.copyFromUnchecked(yuvData.array());

    ScriptIntrinsicYuvToRGB scriptYuvToRgb = ScriptIntrinsicYuvToRGB.create(rs, Element.YUV(rs));
    scriptYuvToRgb.setInput(yuvAllocation);
    scriptYuvToRgb.forEach(rgbAllocation);

    // Get the bitmap

    Bitmap bitmap = Bitmap.createBitmap(image.getWidth(), image.getHeight(), Bitmap.Config.ARGB_8888);
    rgbAllocation.copyTo(bitmap);

    // Release

    bitmap.recycle();

    yuvAllocation.destroy();
    rgbAllocation.destroy();
    rs.destroy();

    image.close();
}

Answer 1

在回答我自己的问题时，实际的问题正如我所怀疑的那样，是如何将图像平面转换为字节缓冲区的。接下来是解决方案，它应该适用于NV21和YV12。由于YUV数据已经在不同的平面上出现，所以只是一个根据行和像素步幅以正确的方式获得它的问题。还需要对如何将数据传递到RenderScript内部进行一些小的修改。

注意：对于经过生产优化的onImageAvailable（）不间断流，在执行转换之前，应该将图像字节数据复制到单独的缓冲区中，并在单独的线程中执行转换（取决于您的需求）。但由于这不是问题的一部分，在下一段代码中，转换直接放在onImageAvailable（）中，以简化答案。如果有人需要知道如何复制图像数据，请创建一个新的问题，让我知道，这样我将分享我的代码。

@Override
public void onImageAvailable(ImageReader reader)
{
    // Get the YUV data

    final Image image = reader.acquireLatestImage();
    final ByteBuffer yuvBytes = this.imageToByteBuffer(image);

    // Convert YUV to RGB

    final RenderScript rs = RenderScript.create(this.mContext);

    final Bitmap        bitmap     = Bitmap.createBitmap(image.getWidth(), image.getHeight(), Bitmap.Config.ARGB_8888);
    final Allocation allocationRgb = Allocation.createFromBitmap(rs, bitmap);

    final Allocation allocationYuv = Allocation.createSized(rs, Element.U8(rs), yuvBytes.array().length);
    allocationYuv.copyFrom(yuvBytes.array());

    ScriptIntrinsicYuvToRGB scriptYuvToRgb = ScriptIntrinsicYuvToRGB.create(rs, Element.U8_4(rs));
    scriptYuvToRgb.setInput(allocationYuv);
    scriptYuvToRgb.forEach(allocationRgb);

    allocationRgb.copyTo(bitmap);

    // Release

    bitmap.recycle();

    allocationYuv.destroy();
    allocationRgb.destroy();
    rs.destroy();

    image.close();
}

private ByteBuffer imageToByteBuffer(final Image image)
{
    final Rect crop   = image.getCropRect();
    final int  width  = crop.width();
    final int  height = crop.height();

    final Image.Plane[] planes     = image.getPlanes();
    final byte[]        rowData    = new byte[planes[0].getRowStride()];
    final int           bufferSize = width * height * ImageFormat.getBitsPerPixel(ImageFormat.YUV_420_888) / 8;
    final ByteBuffer    output     = ByteBuffer.allocateDirect(bufferSize);

    int channelOffset = 0;
    int outputStride = 0;

    for (int planeIndex = 0; planeIndex < 3; planeIndex++)
    {
        if (planeIndex == 0)
        {
            channelOffset = 0;
            outputStride = 1;
        }
        else if (planeIndex == 1)
        {
            channelOffset = width * height + 1;
            outputStride = 2;
        }
        else if (planeIndex == 2)
        {
            channelOffset = width * height;
            outputStride = 2;
        }

        final ByteBuffer buffer      = planes[planeIndex].getBuffer();
        final int        rowStride   = planes[planeIndex].getRowStride();
        final int        pixelStride = planes[planeIndex].getPixelStride();

        final int shift         = (planeIndex == 0) ? 0 : 1;
        final int widthShifted  = width >> shift;
        final int heightShifted = height >> shift;

        buffer.position(rowStride * (crop.top >> shift) + pixelStride * (crop.left >> shift));

        for (int row = 0; row < heightShifted; row++)
        {
            final int length;

            if (pixelStride == 1 && outputStride == 1)
            {
                length = widthShifted;
                buffer.get(output.array(), channelOffset, length);
                channelOffset += length;
            }
            else
            {
                length = (widthShifted - 1) * pixelStride + 1;
                buffer.get(rowData, 0, length);

                for (int col = 0; col < widthShifted; col++)
                {
                    output.array()[channelOffset] = rowData[col * pixelStride];
                    channelOffset += outputStride;
                }
            }

            if (row < heightShifted - 1)
            {
                buffer.position(buffer.position() + rowStride - length);
            }
        }
    }

    return output;
}