mpv/libvo/bitmap_packer.c

/*
 * Calculate how to pack bitmap rectangles into a larger surface
 *
 * Copyright 2009, 2012 Uoti Urpala
 *
 * This file is part of mplayer2.
 *
 * mplayer2 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.
 *
 * mplayer2 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with mplayer2.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdlib.h>

#include <libavutil/common.h>

#include "talloc.h"
#include "bitmap_packer.h"
#include "mp_msg.h"
#include "mpcommon.h"
#include "sub/ass_mp.h"


#define HEIGHT_SORT_BITS 4
static int size_index(int s)
{
    int n = av_log2_16bit(s);
    return (n << HEIGHT_SORT_BITS)
       + (- 1 - (s << HEIGHT_SORT_BITS >> n) & (1 << HEIGHT_SORT_BITS) - 1);
}

/* Pack the given rectangles into an area of size w * h.
 * The size of each rectangle is read from in[i].x / in[i].y.
 * The height of each rectangle must be less than 65536.
 * 'scratch' must point to work memory for num_rects+16 ints.
 * The packed position for rectangle number i is set in out[i].
 * Return 0 on success, -1 if the rectangles did not fit in w*h.
 *
 * The rectangles are placed in rows in order approximately sorted by
 * height (the approximate sorting is simpler than a full one would be,
 * and allows the algorithm to work in linear time). Additionally, to
 * reduce wasted space when there are a few tall rectangles, empty
 * lower-right parts of rows are filled recursively when the size of
 * rectangles in the row drops past a power-of-two threshold. So if a
 * row starts with rectangles of size 3x50, 10x40 and 5x20 then the
 * free rectangle with corners (13, 20)-(w, 50) is filled recursively.
 */
static int pack_rectangles(struct pos *in, struct pos *out, int num_rects,
                           int w, int h, int *scratch)
{
    int bins[16 << HEIGHT_SORT_BITS];
    int sizes[16 << HEIGHT_SORT_BITS] = { 0 };
    for (int i = 0; i < num_rects; i++)
        sizes[size_index(in[i].y)]++;
    int idx = 0;
    for (int i = 0; i < 16 << HEIGHT_SORT_BITS; i += 1 << HEIGHT_SORT_BITS) {
        for (int j = 0; j < 1 << HEIGHT_SORT_BITS; j++) {
            bins[i + j] = idx;
            idx += sizes[i + j];
        }
        scratch[idx++] = -1;
    }
    for (int i = 0; i < num_rects; i++)
        scratch[bins[size_index(in[i].y)]++] = i;
    for (int i = 0; i < 16; i++)
        bins[i] = bins[i << HEIGHT_SORT_BITS] - sizes[i << HEIGHT_SORT_BITS];
    struct {
        int size, x, bottom;
    } stack[16] = {{15, 0, h}}, s = {};
    int stackpos = 1;
    int y;
    while (stackpos) {
        y = s.bottom;
        s = stack[--stackpos];
        s.size++;
        while (s.size--) {
            int maxy = -1;
            int obj;
            while ((obj = scratch[bins[s.size]]) >= 0) {
                int bottom = y + in[obj].y;
                if (bottom > s.bottom)
                    break;
                int right = s.x + in[obj].x;
                if (right > w)
                    break;
                bins[s.size]++;
                out[obj] = (struct pos){s.x, y};
                num_rects--;
                if (maxy < 0)
                    stack[stackpos++] = s;
                s.x = right;
                maxy = FFMAX(maxy, bottom);
            }
            if (maxy > 0)
                s.bottom = maxy;
        }
    }
    return num_rects ? -1 : 0;
}

int packer_pack(struct bitmap_packer *packer)
{
    if (packer->count == 0)
        return 0;
    int w_orig = packer->w, h_orig = packer->h;
    struct pos *in = packer->in;
    int xmax = 0, ymax = 0;
    for (int i = 0; i < packer->count; i++) {
        if (in[i].x == 0 || in[i].y == 0)
            in[i] = (struct pos){0, 0};
        if (in[i].x < 0 || in [i].x > 65535 || in[i].y < 0 || in[i].y > 65535) {
            mp_msg(MSGT_VO, MSGL_FATAL, "Invalid OSD / subtitle bitmap size\n");
            abort();
        }
        xmax = FFMAX(xmax, in[i].x);
        ymax = FFMAX(ymax, in[i].y);
    }
    if (xmax > packer->w)
        packer->w = 1 << av_log2(xmax - 1) + 1;
    if (ymax > packer->h)
        packer->h = 1 << av_log2(ymax - 1) + 1;
    while (1) {
        if (pack_rectangles(in, packer->result, packer->count, packer->w,
                            packer->h, packer->scratch) >= 0)
            return packer->w != w_orig || packer->h != h_orig;
        if (packer->w <= packer->h && packer->w != packer->w_max)
            packer->w = FFMIN(packer->w * 2, packer->w_max);
        else if (packer->h != packer->h_max)
            packer->h = FFMIN(packer->h * 2, packer->h_max);
        else
            return -1;
    }
}

void packer_set_size(struct bitmap_packer *packer, int size)
{
    packer->count = size;
    if (size <= packer->asize)
        return;
    packer->asize = FFMAX(packer->asize * 2, size);
    talloc_free(packer->result);
    talloc_free(packer->scratch);
    packer->in = talloc_realloc(packer, packer->in, struct pos, packer->asize);
    packer->result = talloc_array_ptrtype(packer, packer->result,
                                          packer->asize);
    packer->scratch = talloc_array_ptrtype(packer, packer->scratch,
                                           packer->asize + 16);
}

int packer_pack_from_assimg(struct bitmap_packer *packer,
                            struct ass_image *imglist)
{
    int count = 0;
    struct ass_image *img = imglist;
    while (img) {
        if (count >= packer->asize)
            packer_set_size(packer, FFMAX(packer->asize * 2, 32));
        packer->in[count].x = img->w;
        packer->in[count].y = img->h;
        img = img->next;
        count++;
    }
    packer->count = count;
    return packer_pack(packer);
}