直接对nv21的数据进行resize。
这是之前项目组遗留的一段代码改过来的。结果不太好。

void Scaler::Resize_NV(const Buffer *src,
                       Buffer *dst){
  // this function have some problem
  if (src->width == dst->width && src->height == dst->height) {
    memcpy(dst->data[0], src->data[0], (dst->width * dst->height * 3 / 2) * sizeof(uint8_t));
    return;
  }
  int srcy, srcx, src_index;
  int xrIntFloat_16 = (src->width << 16) / dst->width + 1;
  int yrIntFloat_16 = (src->height  << 16) / dst->height + 1;

  uint8_t* dst_uv = dst->data[0] + dst->height * dst->width;
  dst->data[1] = dst_uv;
  uint8_t* src_uv = src->data[0] + src->height * src->width;
  uint8_t* dst_uv_yScanline = nullptr;
  uint8_t* src_uv_yScanline = nullptr;
  uint8_t* dst_y_slice = dst->data[0];
  uint8_t* src_y_slice = nullptr;
  uint8_t* sp = nullptr;
  uint8_t* dp = nullptr;

  for (uint32_t y = 0; y < (dst->height & -7); ++y) {
    srcy = (y * yrIntFloat_16) >> 16;
    src_y_slice = src->data[0] + srcy * src->width;
    if (0 == (y & 1)) {
      dst_uv_yScanline = dst_uv + (y / 2) * dst->width;
      src_uv_yScanline = src_uv + (srcy / 2) * src->width;
    }
    for (uint32_t x = 0; x < (dst->width & -7); ++x) {
      srcx = (x * xrIntFloat_16) >> 16;
      dst_y_slice[x] = src_y_slice[srcx];
      if ((y & 1) == 0) {    // y is even
        if ((x & 1) == 0) {  // x is even
          src_index = (srcx / 2) * 2;
          sp = dst_uv_yScanline + x;
          dp = src_uv_yScanline + src_index;
          *sp = *dp;
          ++sp;
          ++dp;
          *sp = *dp;
        }
      }
    }
    dst_y_slice += dst->width;
  }

  dst->stride[0] = dst->width;
  dst->stride[1] = dst->width;
  dst->stride[2] = 0;
  dst->color = src->color;
}

结果

原图

结果

这结果明显有黑色的线条，不对啊。

后面我用libyuv实现了下nv的resize。
libyuv实现nv resize