Document the RGBA structure

Author: Reini Urban

common/include/pcl/impl/point_types.hpp

@@ -342,20 +342,20 @@ namespace pcl
  PCL_EXPORTS std::ostream& operator << (std::ostream& os, const RGB& p);
  /** \brief A structure representing RGB color information.
  *
- * The RGBA information is available either as separate r, g, b, or as a
- * packed std::uint32_t rgba value. To pack it, use:
+ * The RGB information is available either as separate r, g, b or as a
+ * packed std::uint32_t rgb value. To pack it, use:
  *
  * \code
- * int rgb = ((int)r) << 16 | ((int)g) << 8 | ((int)b);
+ * std::uint32_t rgb = ((int)r) << 16 | ((int)g) << 8 | ((int)b);
  * \endcode
  *
  * To unpack it use:
  *
  * \code
- * int rgb = ...;
+ * std::uint32_t rgb = p.rgba;
  * std::uint8_t r = (rgb >> 16) & 0x0000ff;
  * std::uint8_t g = (rgb >> 8) & 0x0000ff;
- * std::uint8_t b = (rgb) & 0x0000ff;
+ * std::uint8_t b = (rgb)  & 0x0000ff;
  * \endcode
  *
  */
@@ -506,20 +506,22 @@ namespace pcl
  PCL_EXPORTS std::ostream& operator << (std::ostream& os, const PointXYZRGBA& p);
  /** \brief A point structure representing Euclidean xyz coordinates, and the RGBA color.
  *
- * The RGBA information is available either as separate r, g, b, or as a
- * packed std::uint32_t rgba value. To pack it, use:
+ * The RGBA information is available either as separate r, g, b and a uint8_t values,
+ * or as a packed std::uint32_t rgba value. To pack it, use:
  *
  * \code
- * int rgb = ((int)r) << 16 | ((int)g) << 8 | ((int)b);
+ * std::uint32_t rgba = ((std::uint32_t)a << 24 | ((std::uint32_t)r << 16 | ((std::uint32_t)g << 8) | b;
  * \endcode
  *
  * To unpack it use:
  *
  * \code
- * int rgb = ...;
+ * // unpack rgb into r/g/b
+ * std::uint32_t rgb = p.rgba;
+ * std::uint8_t a = (rgb >> 24) & 0x0000ff;
  * std::uint8_t r = (rgb >> 16) & 0x0000ff;
  * std::uint8_t g = (rgb >> 8) & 0x0000ff;
- * std::uint8_t b = (rgb) & 0x0000ff;
+ * std::uint8_t b = (rgb)  & 0x0000ff;
  * \endcode
  *
  * \ingroup common
@@ -579,7 +581,7 @@ namespace pcl
  * \code
  * PointXYZRGB p;
  * // unpack rgb into r/g/b
- * std::uint32_t rgb = *reinterpret_cast<int*>(&p.rgb);
+ * std::uint32_t rgb = p.rgb;
  * std::uint8_t r = (rgb >> 16) & 0x0000ff;
  * std::uint8_t g = (rgb >> 8) & 0x0000ff;
  * std::uint8_t b = (rgb) & 0x0000ff;
@@ -899,7 +901,7 @@ namespace pcl
  * \code
  * PointXYZRGB p;
  * // unpack rgb into r/g/b
- * std::uint32_t rgb = *reinterpret_cast<int*>(&p.rgb);
+ * std::uint32_t rgb = p.rgba;
  * std::uint8_t r = (rgb >> 16) & 0x0000ff;
  * std::uint8_t g = (rgb >> 8) & 0x0000ff;
  * std::uint8_t b = (rgb) & 0x0000ff;