File indexing completed on 2024-05-12 04:44:33

 // SPDX-FileCopyrightText: Lukas Sommer <sommerluk@gmail.com>
 // SPDX-License-Identifier: BSD-2-Clause OR MIT
 
 #ifndef InterlacingPass_H
 #define InterlacingPass_H
 
 #include "helpermath.h"
 #include <qsize.h>
 
 namespace PerceptualColor
 {
 /** @internal
  *
  * @brief Describes an interlacing pass.
  *
  * Objects of this class provide information about interlacing passes
  * for <a href="https://en.wikipedia.org/wiki/Adam7_algorithm">Adam7</a>-like
  * interlacing.
  *
  * To do <a href="https://en.wikipedia.org/wiki/Adam7_algorithm">Adam7</a>
  * interlacing, construct an object of this class with a <tt>passCount</tt>
  * of <tt>7</tt>. Do the first pass using the values provided
  * by this object. Then, call @ref switchToNextPass to update the
  * values and do the next interlacing pass.
  *
  * The pixels in your image are divided in lines, who in turn are subdivided
  * in columns. Within each interlacing pass, go through every
  * @ref lineFrequency th line, starting with the line at @ref lineOffset.
  * Within each line, go through every @ref columnFrequency th column, starting
  * with @ref columnOffset. Draw a rectangle with the size @ref rectangleSize
  * who’s top-left pixel is at the current column and line.
  *
  * @note As this is just an internal class which is not part of the public API,
  * there is direct access to its data members for simplicity reasons. However,
  * it is not allowed to change them directly! Use them read-only. */
 class InterlacingPass final
 {
 public:
     /** @brief Constructor
      *
      * Constructs an object for a new interlacing cycle.
      *
      * @tparam passCount Number of passes within this interlacing
      * cycle. This MUST be a positive odd number. Use <tt>7</tt>
      * for <a href="https://en.wikipedia.org/wiki/Adam7_algorithm">Adam7</a>
      * interlacing, or any other positive odd number for
      * <a href="https://en.wikipedia.org/wiki/Adam7_algorithm">Adam7</a>-like
      * interlacing, but with a different number of steps.
      *
      * @returns A corresponding object. */
     template<int passCount>
     static InterlacingPass make()
     {
         static_assert(passCount > 0, "passCount must be positive.");
         static_assert(isOdd(passCount), "passCount must be odd.");
         return InterlacingPass(passCount);
     }
 
     void switchToNextPass();
 
     /** @brief Size of the rectangles drawn during this pass. */
     QSize rectangleSize;
     /** @brief Draw a rectangle every umpteenth column. */
     int columnFrequency;
     /** @brief First column on a given line to draw a rectangle. */
     int columnOffset;
     /** @brief Draw a rectangle every umpteenth line. */
     int lineFrequency;
     /** @brief First line to process. */
     int lineOffset;
     /** @brief Pass countdown.
      *
      * Inverse counting of the interlacing passes.
      *
      * Example for
      * <a href="https://en.wikipedia.org/wiki/Adam7_algorithm">Adam7</a>:
      *
      * |    Pass     | @ref countdown |
      * | :---------- | :------------: |
      * | 1st         |       7        |
      * | 2nd         |       6        |
      * | 3rd         |       5        |
      * | 4th         |       4        |
      * | 5th         |       3        |
      * | 6th         |       2        |
      * | 7th (last)  |       1        | */
     int countdown;
 
 private:
     explicit InterlacingPass(const int passCount);
 
     /** @internal @brief Only for unit tests. */
     friend class TestInterlacingPass;
 };
 
 } // namespace PerceptualColor
 
 #endif // InterlacingPass_H