fltk/FL/Fl_Shared_Image.H

//
// Shared image header file for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2021 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file.  If this
// file is missing or damaged, see the license at:
//
//     https://www.fltk.org/COPYING.php
//
// Please see the following page on how to report bugs and issues:
//
//     https://www.fltk.org/bugs.php
//

/** \file
   Fl_Shared_Image class. */

#ifndef Fl_Shared_Image_H
#  define Fl_Shared_Image_H

#  include "Fl_Image.H"


/** Test function (typedef) for adding new shared image formats.

  This defines the function type you can use to add a handler for unknown
  image formats that can be opened and loaded as an Fl_Shared_Image.

  fl_register_images() adds all image formats known to FLTK.
  Call Fl_Shared_Image::add_handler() to add your own check function to
  the list of known image formats.

  Your function will be passed the filename (\p name), some \p header
  bytes already read from the image file and the size \p headerlen of the
  data read. The max value of size is implementation dependent. If your
  handler function needs to check more bytes you must open the image file
  yourself.

  The provided buffer \p header must not be overwritten.

  If your handler function can identify the file type you must open the
  file and return a valid Fl_Image or derived type, otherwise you must
  return \c NULL.
  Example:
  \code
    static Fl_Image *check_my_image(const char *name,
                                    uchar *header,
                                    int headerlen) {
      // (test image type using header and headerlen)
      if (known) {
        // (load image data from file \p name)
        return new Fl_RGB_Image(data, ...);
      } else
        return 0;
    }
    // add your handler:
    Fl_Shared_Image::add_handler(check_my_image);
  \endcode

  \param[in]    name        filename to be checked and opened if applicable
  \param[in]    header      portion of the file that has already been read
  \param[in]    headerlen   length of provided \p header data

  \returns      valid Fl_Image or \c NULL.

  \see Fl_Shared_Image::add_handler()
*/
typedef Fl_Image *(*Fl_Shared_Handler)(const char *name,
                                       uchar *header,
                                       int headerlen);

/**
  This class supports caching, loading, and drawing of image files.

  Most applications will also want to link against the fltk_images library
  and call the fl_register_images() function to support standard image
  formats such as BMP, GIF, JPEG, PNG, and SVG (unless the library was built
  with the option removing SVG support).

  Images can be requested (loaded) with Fl_Shared_Image::get(), find(),
  and some other methods. All images are cached in an internal list of
  shared images and should be released when they are no longer needed.
  A refcount is used to determine if a released image is to be destroyed
  with delete.

  \see fl_register_image()
  \see Fl_Shared_Image::get()
  \see Fl_Shared_Image::find()
  \see Fl_Shared_Image::release()
*/
class FL_EXPORT Fl_Shared_Image : public Fl_Image {

  friend class Fl_JPEG_Image;
  friend class Fl_PNG_Image;
  friend class Fl_Graphics_Driver;

protected:

  static Fl_Shared_Image **images_;     // Shared images
  static int    num_images_;            // Number of shared images
  static int    alloc_images_;          // Allocated shared images
  static Fl_Shared_Handler *handlers_;  // Additional format handlers
  static int    num_handlers_;          // Number of format handlers
  static int    alloc_handlers_;        // Allocated format handlers

  const char    *name_;                 // Name of image file
  int           original_;              // Original image?
  int           refcount_;              // Number of times this image has been used
  Fl_Image      *image_;                // The image that is shared
  int           alloc_image_;           // Was the image allocated?

  static int    compare(Fl_Shared_Image **i0, Fl_Shared_Image **i1);

  // Use get() and release() to load/delete images in memory...
  Fl_Shared_Image();
  Fl_Shared_Image(const char *n, Fl_Image *img = 0);
  virtual ~Fl_Shared_Image();
  void add();
  void update();

public:
  /** Returns the filename of the shared image */
  const char    *name() { return name_; }

  /** Returns the number of references of this shared image.
    When reference is below 1, the image is deleted.
  */
  int           refcount() { return refcount_; }

  /** Returns whether this is an original image.
    Images loaded from a file or from memory are marked \p original as
    opposed to images created as a copy of another image with different
    size (width or height).
    \note This is useful for debugging (rarely used in user code).
    \since FLTK 1.4.0
  */
  int original() { return original_; }

  void          release();
  void          reload();

  virtual Fl_Shared_Image *as_shared_image() {
    return this;
  }

  virtual Fl_Image *copy(int W, int H);
  Fl_Image *copy() { return Fl_Image::copy(); }
  virtual void color_average(Fl_Color c, float i);
  virtual void desaturate();
  virtual void draw(int X, int Y, int W, int H, int cx = 0, int cy = 0);
  void draw(int X, int Y) { draw(X, Y, w(), h(), 0, 0); }
  virtual void uncache();

  static Fl_Shared_Image *find(const char *name, int W = 0, int H = 0);
  static Fl_Shared_Image *get(const char *name, int W = 0, int H = 0);
  static Fl_Shared_Image *get(Fl_RGB_Image *rgb, int own_it = 1);
  static Fl_Shared_Image **images();
  static int            num_images();
  static void           add_handler(Fl_Shared_Handler f);
  static void           remove_handler(Fl_Shared_Handler f);
};

//
// The following function is provided in the fltk_images library and
// registers all of the "extra" image file formats that are not part
// of the core FLTK library...
//

FL_EXPORT extern void fl_register_images();

#endif // !Fl_Shared_Image_H