include/usb_cam/formats/yuyv.hpp

// Copyright 2023 Evan Flynn
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#ifndef USB_CAM__FORMATS__YUYV_HPP_
#define USB_CAM__FORMATS__YUYV_HPP_

#include "linux/videodev2.h"

#include "usb_cam/formats/pixel_format_base.hpp"
#include "usb_cam/formats/utils.hpp"


namespace usb_cam
{
namespace formats
{

class YUYV : public pixel_format_base
{
public:
  explicit YUYV(const format_arguments_t & args = format_arguments_t())
  : pixel_format_base(
      "yuyv",
      V4L2_PIX_FMT_YUYV,
      usb_cam::constants::YUV422_YUY2,
      2,
      8,
      false)
  {
    (void)args;
  }
};


class YUYV2RGB : public pixel_format_base
{
public:
  explicit YUYV2RGB(const format_arguments_t & args = format_arguments_t())
  : pixel_format_base(
      "yuyv2rgb",
      V4L2_PIX_FMT_YUYV,
      usb_cam::constants::RGB8,
      3,
      8,
      true),
    m_number_of_pixels(args.pixels)
  {}

  /// @brief In this format each four bytes is two pixels.
  /// Each four bytes is two Y's, a Cb and a Cr.
  /// Each Y goes to one of the pixels, and the Cb and Cr belong to both pixels.
  /// As you can see, the Cr and Cb components have half the horizontal resolution
  /// of the Y component. V4L2_PIX_FMT_YUYV is known in the Windows environment as YUY2.
  ///
  /// Source: https://www.linuxtv.org/downloads/v4l-dvb-apis-old/V4L2-PIX-FMT-YUYV.html
  ///
  void convert(const char * & src, char * & dest, const int & bytes_used) override
  {
    (void)bytes_used;    // not used by this conversion method
    int i, j;
    unsigned char y0, y1, u, v;
    unsigned char r, g, b;

    /// Total number of bytes should be 2 * number of pixels. Achieve this by bit-shifting
    /// (NumPixels << 1). See format description above.
    for (i = 0, j = 0; i < (m_number_of_pixels << 1); i += 4, j += 6) {
      y0 = (unsigned char)src[i + 0];
      u = (unsigned char)src[i + 1];
      y1 = (unsigned char)src[i + 2];
      v = (unsigned char)src[i + 3];
      YUV2RGB(y0, u, v, &r, &g, &b);
      dest[j + 0] = r;
      dest[j + 1] = g;
      dest[j + 2] = b;
      YUV2RGB(y1, u, v, &r, &g, &b);
      dest[j + 3] = r;
      dest[j + 4] = g;
      dest[j + 5] = b;
    }
  }

private:
  int m_number_of_pixels;
};

}  // namespace formats
}  // namespace usb_cam

#endif  // USB_CAM__FORMATS__YUYV_HPP_