【opencv源码解析】 二、 cvtColor

这里以CV_BGR2YUV_I420来讲

1. opencv244

core.cpp

void cv::cvtColor( InputArray _src, OutputArray _dst, int code, int dcn )
{
  ...
case COLOR_RGB2YUV_YV12: case COLOR_BGR2YUV_YV12: case COLOR_RGBA2YUV_YV12: case COLOR_BGRA2YUV_YV12:
case COLOR_RGB2YUV_IYUV: case COLOR_BGR2YUV_IYUV: case COLOR_RGBA2YUV_IYUV: case COLOR_BGRA2YUV_IYUV:
if (dcn <= 0) dcn = 1;
uidx = (code == COLOR_BGR2YUV_IYUV || code == COLOR_BGRA2YUV_IYUV || code == COLOR_RGB2YUV_IYUV || code == COLOR_RGBA2YUV_IYUV) ? 1 : 2;
CV_Assert( (scn == 3 || scn == 4) && depth == CV_8U );
CV_Assert( dcn == 1 );
CV_Assert( sz.width % 2 == 0 && sz.height % 2 == 0 );
_dst.create(Size(sz.width, sz.height / 2 * 3), CV_MAKETYPE(depth, dcn));
dst = _dst.getMat();
hal::cvtBGRtoThreePlaneYUV(src.data, src.step, dst.data, dst.step, src.cols, src.rows,
scn, swapBlue(code), uidx);
break;

  ...
}

　　

color.cpp

void cvtBGRtoThreePlaneYUV(const uchar * src_data, size_t src_step,
uchar * dst_data, size_t dst_step,
int width, int height,
int scn, bool swapBlue, int uIdx)
{
CV_INSTRUMENT_REGION()

CALL_HAL(cvtBGRtoThreePlaneYUV, cv_hal_cvtBGRtoThreePlaneYUV, src_data, src_step, dst_data, dst_step, width, height, scn, swapBlue, uIdx);
uchar * uv_data = dst_data + dst_step * height;
RGB888toYUV420pInvoker(src_data, src_step, dst_data, uv_data, dst_step, width, height, scn, swapBlue, uIdx == 2, false).convert();
}

　　

color.cpp

struct RGB888toYUV420pInvoker: public ParallelLoopBody
{
RGB888toYUV420pInvoker(const uchar * _src_data, size_t _src_step,
uchar * _y_data, uchar * _uv_data, size_t _dst_step,
int _src_width, int _src_height, int _scn, bool swapBlue_, bool swapUV_, bool interleaved_)
: src_data(_src_data), src_step(_src_step),
y_data(_y_data), uv_data(_uv_data), dst_step(_dst_step),
src_width(_src_width), src_height(_src_height),
scn(_scn), swapBlue(swapBlue_), swapUV(swapUV_), interleaved(interleaved_) { }

void operator()(const Range& rowRange) const
{
const int w = src_width;
const int h = src_height;
const int cn = scn;
for( int i = rowRange.start; i < rowRange.end; i++ )
{
const uchar* brow0 = src_data + src_step * (2 * i);
const uchar* grow0 = brow0 + 1;
const uchar* rrow0 = brow0 + 2;
const uchar* brow1 = src_data + src_step * (2 * i + 1);
const uchar* grow1 = brow1 + 1;
const uchar* rrow1 = brow1 + 2;
if (swapBlue)
{
std::swap(brow0, rrow0);
std::swap(brow1, rrow1);
}

uchar* y = y_data + dst_step * (2*i);
uchar* u;
uchar* v;
if (interleaved)
{
u = uv_data + dst_step * i;
v = uv_data + dst_step * i + 1;
}
else
{
u = uv_data + dst_step * (i/2) + (i % 2) * (w/2);
v = uv_data + dst_step * ((i + h/2)/2) + ((i + h/2) % 2) * (w/2);
}

if (swapUV)
{
std::swap(u, v);
}

for( int j = 0, k = 0; j < w * cn; j += 2 * cn, k++ )
{
int r00 = rrow0[j]; int g00 = grow0[j]; int b00 = brow0[j];
int r01 = rrow0[cn + j]; int g01 = grow0[cn + j]; int b01 = brow0[cn + j];
int r10 = rrow1[j]; int g10 = grow1[j]; int b10 = brow1[j];
int r11 = rrow1[cn + j]; int g11 = grow1[cn + j]; int b11 = brow1[cn + j];

const int shifted16 = (16 << ITUR_BT_601_SHIFT);
const int halfShift = (1 << (ITUR_BT_601_SHIFT - 1));
int y00 = ITUR_BT_601_CRY * r00 + ITUR_BT_601_CGY * g00 + ITUR_BT_601_CBY * b00 + halfShift + shifted16;
int y01 = ITUR_BT_601_CRY * r01 + ITUR_BT_601_CGY * g01 + ITUR_BT_601_CBY * b01 + halfShift + shifted16;
int y10 = ITUR_BT_601_CRY * r10 + ITUR_BT_601_CGY * g10 + ITUR_BT_601_CBY * b10 + halfShift + shifted16;
int y11 = ITUR_BT_601_CRY * r11 + ITUR_BT_601_CGY * g11 + ITUR_BT_601_CBY * b11 + halfShift + shifted16;

y[2*k + 0] = saturate_cast<uchar>(y00 >> ITUR_BT_601_SHIFT);
y[2*k + 1] = saturate_cast<uchar>(y01 >> ITUR_BT_601_SHIFT);
y[2*k + dst_step + 0] = saturate_cast<uchar>(y10 >> ITUR_BT_601_SHIFT);
y[2*k + dst_step + 1] = saturate_cast<uchar>(y11 >> ITUR_BT_601_SHIFT);

const int shifted128 = (128 << ITUR_BT_601_SHIFT);
int u00 = ITUR_BT_601_CRU * r00 + ITUR_BT_601_CGU * g00 + ITUR_BT_601_CBU * b00 + halfShift + shifted128;
int v00 = ITUR_BT_601_CBU * r00 + ITUR_BT_601_CGV * g00 + ITUR_BT_601_CBV * b00 + halfShift + shifted128;

if (interleaved)
{
u[k*2] = saturate_cast<uchar>(u00 >> ITUR_BT_601_SHIFT);
v[k*2] = saturate_cast<uchar>(v00 >> ITUR_BT_601_SHIFT);
}
else
{
u[k] = saturate_cast<uchar>(u00 >> ITUR_BT_601_SHIFT);
v[k] = saturate_cast<uchar>(v00 >> ITUR_BT_601_SHIFT);
}
}
}
}

void convert() const
{
if( src_width * src_height >= 320*240 )
parallel_for_(Range(0, src_height/2), *this);
else
operator()(Range(0, src_height/2));
}

private:
RGB888toYUV420pInvoker& operator=(const RGB888toYUV420pInvoker&);

const uchar * src_data;
size_t src_step;
uchar *y_data, *uv_data;
size_t dst_step;
int src_width;
int src_height;
const int scn;
bool swapBlue;
bool swapUV;
bool interleaved;
};

　　

2.   opencv347   使用opencl

bool oclCvtColorTwoPlaneYUV2BGR( InputArray _src, OutputArray _dst, int dcn, int bidx, int uidx )
{
    OclHelper< Set<1>, Set<3, 4>, Set<CV_8U>, FROM_YUV > h(_src, _dst, dcn);

    if(!h.createKernel("YUV2RGB_NVx", ocl::imgproc::color_yuv_oclsrc,
                       format("-D dcn=%d -D bidx=%d -D uidx=%d", dcn, bidx, uidx)))
    {
        return false;
    }

    return h.run();
}