vf_remove_logo.c

来自「君正早期ucos系统(只有早期的才不没有打包成库),MPLAYER,文件系统,图」· C语言 代码 · 共 910 行 · 第 1/3 页

/*
Copyright 2005 Robert Edele.

e-mail: [e-mail]

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your option)
any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Public License for more
details.

You should have reveived a copy of the GNU General Public License
along with this program; if not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA

__________________________________________________________________________
| Robert Edele                                           Fri. 4-Feb-2005 |
| This program loads a .pgm mask file showing where a logo is and uses   |
| a blur transform to remove the logo.                                   |
|________________________________________________________________________|
*/

/**
 * \file vf_remove_logo.c
 * 
 * \brief Advanced blur-based logo removing filter.

 *     Hello and welcome. This code implements a filter to remove annoying TV
 * logos and other annoying images placed onto a video stream. It works by filling
 * in the pixels that comprise the logo with neighboring pixels. The transform is
 * very loosely based on a gaussian blur, but it is different enough to merit its
 * own paragraph later on. It is a major improvement on the old delogo filter as
 * it both uses a better blurring algorithm and uses a bitmap to use an arbitrary
 * and generally much tighter fitting shape than a rectangle.
 *
 *     The filter requires 1 argument and has no optional arguments. It requires
 * a filter bitmap, which must be in PGM or PPM format. A sample invocation would
 * be -vf remove_logo=/home/username/logo_bitmaps/xyz.pgm.  Pixels with a value of
 * zero are not part of the logo, and non-zero pixels are part of the logo. If you
 * use white (255) for the logo and black (0) for the rest, you will be safe. For
 * making the filter bitmap, I recommend taking a screen capture of a black frame
 * with the logo visible, and then using The GIMP's threshold filter followed by
 * the erode filter once or twice. If needed, little splotches can be fixed
 * manually. Remember that if logo pixels are not covered, the filter quality will
 * be much reduced. Marking too many pixels as part of the logo doesn't hurt as
 * much, but it will increase the amount of blurring needed to cover over the
 * image and will destroy more information than necessary. Additionally, this blur
 * algorithm is O(n) = n^4, where n is the width and height of a hypothetical
 * square logo, so extra pixels will slow things down on a large lo
 *
 *     The logo removal algorithm has two key points. The first is that it
 * distinguishes between pixels in the logo and those not in the logo by using the
 * passed-in bitmap. Pixels not in the logo are copied over directly without being
 * modified and they also serve as source pixels for the logo fill-in. Pixels
 * inside the logo have the mask applied.
 *
 *     At init-time the bitmap is reprocessed internally, and the distance to the
 * nearest edge of the logo (Manhattan distance), along with a little extra to
 * remove rough edges, is stored in each pixel. This is done using an in-place
 * erosion algorithm, and incrementing each pixel that survives any given erosion.
 * Once every pixel is eroded, the maximum value is recorded, and a set of masks
 * from size 0 to this size are generaged. The masks are circular binary masks,
 * where each pixel within a radius N (where N is the size of the mask) is a 1,
 * and all other pixels are a 0. Although a gaussian mask would be more
 * mathematically accurate, a binary mask works better in practice because we
 * generally do not use the central pixels in the mask (because they are in the
 * logo region), and thus a gaussian mask will cause too little blur and thus a
 * very unstable image.
 *
 *     The mask is applied in a special way. Namely, only pixels in the mask that
 * line up to pixels outside the logo are used. The dynamic mask size means that
 * the mask is just big enough so that the edges touch pixels outside the logo, so
 * the blurring is kept to a minimum and at least the first boundary condition is
 * met (that the image function itself is continuous), even if the second boundary
 * condition (that the derivative of the image function is continuous) is not met.
 * A masking algorithm that does preserve the second boundary coundition
 * (perhaps something based on a highly-modified bi-cubic algorithm) should offer
 * even better results on paper, but the noise in a typical TV signal should make
 * anything based on derivatives hopelessly noisy.
 */

#include <uclib.h>
#include <uclib.h>
#include <mplaylib.h>
#include <ctype.h>
#include <inttypes.h>

#include "config.h"
#include "mp_msg.h"
#include "libvo/fastmemcpy.h"

#include "img_format.h"
#include "mp_image.h"
#include "vf.h"

//===========================================================================//

/** \brief Returns the larger of the two arguments. **/
#define max(x,y) ((x)>(y)?(x):(y))
/** \brief Returns the smaller of the two arguments. **/
#define min(x,y) ((x)>(y)?(y):(x))

/**
 * \brief Test if a pixel is part of the logo.
 */
#define test_filter(image, x, y) ((unsigned char) (image->pixel[((y) * image->width) + (x)]))

/**
 * \brief Chooses a slightly larger mask size to improve performance.
 *
 * This function maps the absolute minimum mask size needed to the mask size we'll
 * actually use. f(x) = x (the smallest that will work) will produce the sharpest
 * results, but will be quite jittery. f(x) = 1.25x (what I'm using) is a good
 * tradeoff in my opinion. This will calculate only at init-time, so you can put a
 * long expression here without effecting performance.
 */
#define apply_mask_fudge_factor(x) (((x) >> 2) + x)

/**
 * \brief Simple implementation of the PGM image format.
 *
 * This struct holds a bare-bones image loaded from a PGM or PPM file. Once
 * loaded and pre-processed, each pixel in this struct will contain how far from
 * the edge of the logo each pixel is, using the manhattan distance (|dx| + |dy|).
 *
 * pixels in char * pixel can be addressed using (y * width) + height.
 */
typedef struct
{
  unsigned int width;
  unsigned int height;

  unsigned char * pixel;

} pgm_structure;

/**
 * \brief Stores persistant variables.
 *
 * Variables stored here are kept from frame to frame, and separate instances of
 * the filter will get their own separate copies.
 */
typedef struct
{
  unsigned int fmt; /* Not exactly sure of the use for this. It came with the example filter I used as a basis for this, and it looks like a lot of stuff will break if I remove it. */
  int max_mask_size; /* The largest possible mask size that will be needed with the given filter and corresponding half_size_filter. The half_size_filter can have a larger requirment in some rare (but not degenerate) cases. */
  int * * * mask; /* Stores our collection of masks. The first * is for an array of masks, the second for the y axis, and the third for the x axis. */
  pgm_structure * filter; /* Stores the full-size filter image. This is used to tell what pixels are in the logo or not in the luma plane. */
  pgm_structure * half_size_filter; /* Stores a 50% width and 50% height filter image. This is used to tell what pixels are in the logo or not in the chroma planes. */
  /* These 8 variables store the bounding rectangles that the logo resides in. */
  int bounding_rectangle_posx1;
  int bounding_rectangle_posy1;
  int bounding_rectangle_posx2;
  int bounding_rectangle_posy2;
  int bounding_rectangle_half_size_posx1;
  int bounding_rectangle_half_size_posy1;
  int bounding_rectangle_half_size_posx2;
  int bounding_rectangle_half_size_posy2;
} vf_priv_s;

/**
 * \brief Mallocs memory and checks to make sure it succeeded.
 *
 * \param size How many bytes to allocate.
 *
 * \return A pointer to the freshly allocated memory block, or NULL on failutre.
 *
 * Mallocs memory, and checks to make sure it was successfully allocated. Because
 * of how MPlayer works, it cannot safely halt execution, but at least the user
 * will get an error message before the segfault happens.
 */
static void * safe_malloc(int size)
{
  void * answer = malloc(size);
  if (answer == NULL)
    mp_msg(MSGT_VFILTER, MSGL_ERR, "Unable to allocate memory in vf_remove_logo.c\n");

  return answer;
}

/**
 * \brief Calculates the smallest rectangle that will encompass the logo region.
 *
 * \param filter This image contains the logo around which the rectangle will
 *        will be fitted.
 *
 * The bounding rectangle is calculated by testing successive lines (from the four
 * sides of the rectangle) until no more can be removed without removing logo
 * pixels. The results are returned by reference to posx1, posy1, posx2, and
 * posy2.
 */
static void calculate_bounding_rectangle(int * posx1, int * posy1, int * posx2, int * posy2, pgm_structure * filter)
{
  int x; /* Temporary variables to run  */
  int y; /* through each row or column. */
  int start_x;
  int start_y; 
  int end_x = filter->width - 1;
  int end_y = filter->height - 1;
  int did_we_find_a_logo_pixel = 0;

  /* Let's find the top bound first. */
  for (start_x = 0; start_x < filter->width && !did_we_find_a_logo_pixel; start_x++)
  {
    for (y = 0; y < filter->height; y++)
    {
      did_we_find_a_logo_pixel |= test_filter(filter, start_x, y);
    }
  }
  start_x--;

  /* Now the bottom bound. */
  did_we_find_a_logo_pixel = 0;
  for (end_x = filter->width - 1; end_x > start_x && !did_we_find_a_logo_pixel; end_x--)
  {
    for (y = 0; y < filter->height; y++)
    {
      did_we_find_a_logo_pixel |= test_filter(filter, end_x, y);
    }
  }
  end_x++;

  /* Left bound. */
  did_we_find_a_logo_pixel = 0;
  for (start_y = 0; start_y < filter->height && !did_we_find_a_logo_pixel; start_y++)
  {
    for (x = 0; x < filter->width; x++)
    {
      did_we_find_a_logo_pixel |= test_filter(filter, x, start_y);
    }
  }
  start_y--;

  /* Right bound. */
  did_we_find_a_logo_pixel = 0;
  for (end_y = filter->height - 1; end_y > start_y && !did_we_find_a_logo_pixel; end_y--)
  {
    for (x = 0; x < filter->width; x++)
    {
      did_we_find_a_logo_pixel |= test_filter(filter, x, end_y);
    }
  }
  end_y++;

  *posx1 = start_x;
  *posy1 = start_y;
  *posx2 = end_x;
  *posy2 = end_y;

  return;
}

/**
 * \brief Free mask memory.
 *
 * \param vf Data structure which stores our persistant data, and is to be freed.
 *
 * We call this function when our filter is done. It will free the memory
 * allocated to the masks and leave the variables in a safe state.
 */
static void destroy_masks(vf_instance_t * vf)
{
  int a, b;

  /* Load values from the vf->priv struct for faster dereferencing. */
  int * * * mask = ((vf_priv_s *)vf->priv)->mask;
  int max_mask_size = ((vf_priv_s *)vf->priv)->max_mask_size;

  if (mask == NULL)
    return; /* Nothing allocated, so return before we segfault. */

  /* Free all allocated memory. */
  for (a = 0; a <= max_mask_size; a++) /* Loop through each mask. */
  {
    for (b = -a; b <= a; b++) /* Loop through each scanline in a mask. */
    {
      free(mask[a][b + a]); /* Free a scanline. */
    }
    free(mask[a]); /* Free a mask. */
  }
  free(mask); /* Free the array of pointers pointing to the masks. */

  /* Set the pointer to NULL, so that any duplicate calls to this function will not cause a crash. */
  ((vf_priv_s *)vf->priv)->mask = NULL;

  return;
}

/**
 * \brief Set up our array of masks.
 *
 * \param vf Where our filter stores persistance data, like these masks.
 *
 * This creates an array of progressively larger masks and calculates their
 * values. The values will not change during program execution once this function
 * is done.
 */
static void initialize_masks(vf_instance_t * vf)
{