/***********************************************
* file d:\cips\tiff.c
*
* Functions: This file contains
* read_tiff_header
* extract_long_from_buffer
* extract_short_from_buffer
*
* Purpose: This file contains the subroutines
* that read the tiff files header information.
*
* External Calls:
* mof.c - my_open_file
* mrw.c - my_read
*
* Modifications: created 23 June 1990
***********************************************/
#include "d:\cips\cips.h"
read_tiff_header(file_name, image_header)
char file_name[];
struct tiff_header_struct *image_header;
{
char buffer[12];
int bytes_read,
closed,
file_desc,
i,
j,
lsb,
not_finished;
long bits_per_pixel,
image_length,
image_width,
length_of_field,
offset_to_ifd,
position,
strip_offset,
subfile,
value;
short entry_count,
field_type,
s_bits_per_pixel,
s_image_length,
s_image_width,
s_strip_offset,
tag_type;
file_desc = my_open(file_name);
/*************************************
* Determine if the file uses MSB
* first or LSB first
*************************************/
bytes_read = my_read(file_desc, buffer, 8);
if(buffer[0] == 0x49)
lsb = 1;
else
lsb = 0;
/*************************************
* Read the offset to the IFD
*************************************/
extract_long_from_buffer(buffer, lsb, 4,
&offset_to_ifd);
not_finished = 1;
while(not_finished){
/************************************
* Seek to the IFD and read the
* entry_count, i.e. the number of
* entries in the IFD.
*************************************/
position = lseek(file_desc, offset_to_ifd, 0);
bytes_read = my_read(file_desc, buffer, 2);
extract_short_from_buffer(buffer, lsb, 0,
&entry_count);
/***************************************
* Now loop over the directory entries.
* Look only for the tags we need. These are:
* ImageLength
* ImageWidth
* BitsPerPixel(BitsPerSample)
* StripOffset
***************************************/
for(i=0; i<entry_count; i++){
bytes_read = my_read(file_desc, buffer, 12);
extract_short_from_buffer(buffer, lsb, 0,
&tag_type);
switch(tag_type){
case 255: /* Subfile Type */
extract_short_from_buffer(buffer, lsb, 2,
&field_type);
extract_short_from_buffer(buffer, lsb, 4,
&length_of_field);
extract_long_from_buffer(buffer, lsb, 8,
&subfile);
break;
case 256: /* ImageWidth */
extract_short_from_buffer(buffer, lsb, 2,
&field_type);
extract_short_from_buffer(buffer, lsb, 4,
&length_of_field);
extract_long_from_buffer(buffer, lsb, 8,
&subfile);
break;
case 256: /* ImageWidth */
extract_short_from_buffer(buffer, lsb, 2,
&field_type);
extract_short_from_buffer(buffer, lsb, 4,
&length_of_field);
if(field_type == 3){
extract_short_from_buffer(buffer, lsb, 8,
&s_image_width);
image_width = s_image_width;
}
else
extract_long_from_buffer(buffer, lsb, 8,
&image_width);
break;
case 257: /* ImageLength */
extract_short_from_buffer(buffer, lsb, 2,
&field_type);
extract_short_from_buffer(buffer, lsb, 4,
&length of_field);
if(field_type == 3){
extract_short_from_buffer(buffer, lsb, 8,
&s_image_length);
image_length = s_image_length;
}
else
extract_long_from_buffer(buffer, lsb, 8,
&image_length);
break;
case 258: /* BitsPerPixel */
extract_short_from_buffer(buffer, lsb, 2,
&field_type);
extract_short_from_buffer(buffer, lsb, 4,
&length_of_field);
if(field_type == 3){
extract_short_from_buffer(buffer, lsb, 8,
&s_bits_per_pixel);
bits_per_pixel = s_bits_per_pixel;
}
else
extract_long_from_buffer(buffer, lsb, 8,
&bits_per_pixel);
break;
case 273: /* StripOffset */
extract_short_from_buffer(buffer, lsb, 2,
&field_type);
extract_short_from_buffer(buffer, lsb, 4,
&length_of_field);
if(field_type == 3){
extract_short_from_buffer(buffer, lsb, 8,
&s_strip_offset);
strip_offset = s_strip_offset;
}
else
extract_long_from_buffer(buffer, lsb, 8,
&strip_offset);
break;
default:
break;
} /* ends switch tag_type */
} /* ends loop over i directory entries */
bytes_read = my_read(file_desc, buffer, 4);
extract_long_from_buffer(buffer, lsb, 0,
&offset_to_ifd);
if(offset_to_ifd == 0) not_finished = 0;
} /* ends while not_finished */
image_header->lsb = lsb;
image_header->bits_per_pixel = bits_per_pixel;
image_header->image_length = image_length;
image_header->image_width = image_width;
image_header->strip_offset = strip_offset;
closed = close(file_desc);
} /* ends read_tiff_header */
/****************************************
* extract_long_from_buffer(...
*
* This takes a four byte long out of a
* buffer of characters. It is important
* to know the byte order LSB or MSB.
****************************************/
extract_long_from_buffer(buffer, lsb, start, number)
char buffer[];
int lsb, start;
long *number;
{
int i;
union long_char_union lcu;
if(lsb == 1){
lcu.l_alpha[0] = buffer[start+0];
lcu.l_alpha[1] = buffer[start+1];
lcu.l_alpha[2] = buffer[start+2];
lcu.l_alpha[3] = buffer[start+3];
} /* ends if lsb = 1 */
if(lsb == 0){
lcu.l_alpha[0] = buffer[start+3];
lcu.l_alpha[1] = buffer[start+2];
lcu.l_alpha[2] = buffer[start+1];
lcu.l_alpha[3] = buffer[start+0];
} /* ends if lsb = 0 */
*number = lcu.l_num;
} /* ends extract_long_from_buffer */
/****************************************
* extract_short_from_buffer(...
*
* This takes a two byte short out of a
* buffer of characters. It is important
* to know the byte order LSB or MSB.
****************************************/
extract_short_from_buffer(buffer, lsb, start, number)
char buffer[];
int lsb, start;
short *number;
{
int i;
union short_char_union_lcu;
if(lsb == 1){
lcu.s_alpha[0] = buffer[start+0];
lcu.s_alpha[1] = buffer[start+1];
} /* ends if lsb = 1 */
if(lsb == 0){
lcu.s_alpha[0] = buffer[start+1];
lcu.s_alpha[1] = buffer[start+0];
} /* ends if lsb = 0 */
*number = lcu.s_num;
} /* ends extract_short_from_buffer */