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added run length encoding function.

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This commit is contained in:
Eric Smith 2003-02-20 12:11:06 +00:00
parent 03e732c4b5
commit d613cecaa6
2 changed files with 98 additions and 3 deletions
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77
bitblt.c
View File

@ -4,7 +4,7 @@
* will be compressed using ITU-T T.6 (G4) fax encoding.
*
* bitblt routines
* $Id: bitblt.c,v 1.11 2003/02/19 02:14:44 eric Exp $
* $Id: bitblt.c,v 1.12 2003/02/20 04:11:06 eric Exp $
* Copyright 2001, 2002, 2003 Eric Smith <eric@brouhaha.com>
*
* This program is free software; you can redistribute it and/or modify
@ -726,6 +726,79 @@ void rot_270 (Bitmap *src) /* transpose + flip_v */
}
void bitblt_init (void)
int32_t get_row_run_lengths (Bitmap *src,
int32_t y,
int32_t min_x, int32_t max_x,
int32_t max_runs,
uint32_t *run_length)
{
uint8_t *byte_ptr;
uint8_t byte;
int bit_pos;
uint32_t byte_cnt;
int last_bits;
bool last_flag = 0;
uint8_t pol = 0x00; /* 0x00 = counting zeros (white),
0xff = counting ones (black) */
uint32_t rl;
int32_t i = 0;
/* adjust coordinate system */
y -= src->rect.min.y;
min_x -= src->rect.min.x;
max_x -= src->rect.min.x;
byte_ptr = (uint8_t *) (src->bits + y * src->row_words);
byte_cnt = (max_x / 8) + 1 - (min_x / 8);
last_bits = max_x % 8;
rl = 0;
pol = 0x00; /* initially count white pixels */
byte_ptr += min_x / 8;
bit_pos = min_x % 8;
byte = *(byte_ptr++);
/* is the first byte also the last? */
if (--byte_cnt == 0)
{
byte <<= (7 - last_bits); /* last byte may be partial */
bit_pos += (7 - last_bits);
last_flag = 1;
}
for (;;)
{
int b2 = rle_tab [bit_pos] [pol ^ byte];
rl += b2;
bit_pos += b2;
if (bit_pos == 8)
{
if (last_flag)
{
if (rl)
run_length [i++] = rl;
return (i);
}
bit_pos = 0;
byte = *(byte_ptr++);
if (--byte_cnt == 0)
{
byte <<= (7 - last_bits); /* last byte may be partial */
bit_pos += (7 - last_bits);
last_flag = 1;
}
}
else
{
run_length [i++] = rl;
if (i == max_runs)
return (-i);
rl = 0;
pol ^= 0xff;
}
}
}

24
bitblt.h
View File

@ -4,7 +4,7 @@
* will be compressed using ITU-T T.6 (G4) fax encoding.
*
* bitblt routines
* $Id: bitblt.h,v 1.10 2003/02/19 02:14:44 eric Exp $
* $Id: bitblt.h,v 1.11 2003/02/20 04:11:06 eric Exp $
* Copyright 2001, 2002, 2003 Eric Smith <eric@brouhaha.com>
*
* This program is free software; you can redistribute it and/or modify
@ -98,3 +98,25 @@ void rot_270 (Bitmap *src); /* transpose + flip_v */
void reverse_bits (uint8_t *p, int byte_count);
/*
* get_row_run_lengths counts the runs of 0 and 1 bits in row
* y of a bitmap, from min_x through max_x inclusive. The run lengths
* will be stored in the run_length array. The first entry will be
* the length of a zero run (which length may be zero, if the first
* bit is a one). The next entry will the be the length of a run of
* ones, and they will alternate from there, with even entries representing
* runs of zeros, and odd entries representing runs of ones.
*
* max_runs should be set to the maximum number of run lengths that
* can be stored in the run_length array.
*
* Returns the actual number of runs counted, or -max_runs if there
* was not enough room in the array.
*/
int32_t get_row_run_lengths (Bitmap *src,
int32_t y,
int32_t min_x, int32_t max_x,
int32_t max_runs,
uint32_t *run_length);