t4.h

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00001 /*
00002  * SpanDSP - a series of DSP components for telephony
00003  *
00004  * t4.h - definitions for T.4 fax processing
00005  *
00006  * Written by Steve Underwood <steveu@coppice.org>
00007  *
00008  * Copyright (C) 2003 Steve Underwood
00009  *
00010  * All rights reserved.
00011  *
00012  * This program is free software; you can redistribute it and/or modify
00013  * it under the terms of the GNU General Public License version 2, as
00014  * published by the Free Software Foundation.
00015  *
00016  * This program is distributed in the hope that it will be useful,
00017  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00018  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00019  * GNU General Public License for more details.
00020  *
00021  * You should have received a copy of the GNU General Public License
00022  * along with this program; if not, write to the Free Software
00023  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00024  *
00025  * $Id: t4.h,v 1.45 2007/11/26 13:58:06 steveu Exp $
00026  */
00027 
00028 /*! \file */
00029 
00030 #if !defined(_SPANDSP_T4_H_)
00031 #define _SPANDSP_T4_H_
00032 
00033 /*! \page t4_page T.4 image compression and decompression
00034 
00035 \section t4_page_sec_1 What does it do?
00036 The T.4 image compression and decompression routines implement the 1D and 2D
00037 encoding methods defined in ITU specification T.4. They also implement the pure
00038 2D encoding method defined in T.6. These are image compression algorithms used
00039 for FAX transmission.
00040 
00041 \section t4_page_sec_1 How does it work?
00042 */
00043 
00044 typedef int (*t4_row_read_handler_t)(void *user_data, uint8_t buf[], size_t len);
00045 typedef int (*t4_row_write_handler_t)(void *user_data, const uint8_t buf[], size_t len);
00046 
00047 typedef enum
00048 {
00049     T4_COMPRESSION_ITU_T4_1D = 1,
00050     T4_COMPRESSION_ITU_T4_2D = 2,
00051     T4_COMPRESSION_ITU_T6 = 3
00052 } t4_image_compression_t;
00053 
00054 typedef enum
00055 {
00056     T4_X_RESOLUTION_R4 = 4016,
00057     T4_X_RESOLUTION_R8 = 8031,
00058     T4_X_RESOLUTION_300 = 11811,
00059     T4_X_RESOLUTION_R16 = 16063,
00060     T4_X_RESOLUTION_600 = 23622,
00061     T4_X_RESOLUTION_800 = 31496,
00062     T4_X_RESOLUTION_1200 = 47244
00063 } t4_image_x_resolution_t;
00064 
00065 typedef enum
00066 {
00067     T4_Y_RESOLUTION_STANDARD = 3850,
00068     T4_Y_RESOLUTION_FINE = 7700,
00069     T4_Y_RESOLUTION_300 = 11811,
00070     T4_Y_RESOLUTION_SUPERFINE = 15400,  /* 400 is 15748 */
00071     T4_Y_RESOLUTION_600 = 23622,
00072     T4_Y_RESOLUTION_800 = 31496,
00073     T4_Y_RESOLUTION_1200 = 47244
00074 } t4_image_y_resolution_t;
00075 
00076 /*!
00077     Exact widths in PELs for the difference resolutions, and page widths.
00078     Note:
00079         The A4 widths also apply to North American letter and legal.
00080         The R4 resolution widths are not supported in recent versions of T.30
00081         Only images of exactly these widths are acceptable for FAX transmisson.
00082 
00083     R4    864 pels/215mm for ISO A4, North American Letter and Legal
00084     R4   1024 pels/255mm for ISO B4
00085     R4   1216 pels/303mm for ISO A3
00086     R8   1728 pels/215mm for ISO A4, North American Letter and Legal
00087     R8   2048 pels/255mm for ISO B4
00088     R8   2432 pels/303mm for ISO A3
00089     R16  3456 pels/215mm for ISO A4, North American Letter and Legal
00090     R16  4096 pels/255mm for ISO B4
00091     R16  4864 pels/303mm for ISO A3
00092 */
00093 typedef enum
00094 {
00095     T4_WIDTH_R4_A4 = 864,
00096     T4_WIDTH_R4_B4 = 1024,
00097     T4_WIDTH_R4_A3 = 1216,
00098     T4_WIDTH_R8_A4 = 1728,
00099     T4_WIDTH_R8_B4 = 2048,
00100     T4_WIDTH_R8_A3 = 2432,
00101     T4_WIDTH_300_A4 = 2592,
00102     T4_WIDTH_300_B4 = 3072,
00103     T4_WIDTH_300_A3 = 3648,
00104     T4_WIDTH_R16_A4 = 3456,
00105     T4_WIDTH_R16_B4 = 4096,
00106     T4_WIDTH_R16_A3 = 4864,
00107     T4_WIDTH_600_A4 = 5184,
00108     T4_WIDTH_600_B4 = 6144,
00109     T4_WIDTH_600_A3 = 7296,
00110     T4_WIDTH_1200_A4 = 10368,
00111     T4_WIDTH_1200_B4 = 12288,
00112     T4_WIDTH_1200_A3 = 14592
00113 } t4_image_width_t;
00114 
00115 /*!
00116     Length of the various supported paper sizes, in pixels at the various Y resolutions.
00117     Paper sizes are
00118         A4 (215mm x 297mm)
00119         B4 (255mm x 364mm)
00120         A3 (303mm x 418.56mm)
00121         North American Letter (215.9mm x 279.4mm)
00122         North American Legal (215.9mm x 355.6mm)
00123         Unlimited
00124 
00125     T.4 does not accurately define the maximum number of scan lines in a page. A wide
00126     variety of maximum row counts are used in the real world. It is important not to
00127     set our sending limit too high, or a receiving machine might split pages. It is
00128     important not to set it too low, or we might clip pages.
00129 
00130     Values seen for standard resolution A4 pages include 1037, 1045, 1109, 1126 and 1143.
00131     1109 seems the most-popular.  At fine res 2150, 2196, 2200, 2237, 2252-2262, 2264,
00132     2286, and 2394 are used. 2255 seems the most popular. We try to use balanced choices
00133     here.
00134 */
00135 typedef enum
00136 {
00137     /* A4 is 297mm long */
00138     T4_LENGTH_STANDARD_A4 = 1143,
00139     T4_LENGTH_FINE_A4 = 2286,
00140     T4_LENGTH_300_A4 = 4665,
00141     T4_LENGTH_SUPERFINE_A4 = 4573,
00142     T4_LENGTH_600_A4 = 6998,
00143     T4_LENGTH_800_A4 = 9330,
00144     T4_LENGTH_1200_A4 = 13996,
00145     /* B4 is 364mm long */
00146     T4_LENGTH_STANDARD_B4 = 1401,
00147     T4_LENGTH_FINE_B4 = 2802,
00148     T4_LENGTH_300_B4 = 0,
00149     T4_LENGTH_SUPERFINE_B4 = 5605,
00150     T4_LENGTH_600_B4 = 0,
00151     T4_LENGTH_800_B4 = 0,
00152     T4_LENGTH_1200_B4 = 0,
00153     /* North American letter is 279.4mm long */
00154     T4_LENGTH_STANDARD_US_LETTER = 1075,
00155     T4_LENGTH_FINE_US_LETTER = 2151,
00156     T4_LENGTH_300_US_LETTER = 0,
00157     T4_LENGTH_SUPERFINE_US_LETTER = 4302,
00158     T4_LENGTH_600_US_LETTER = 0,
00159     T4_LENGTH_800_US_LETTER = 0,
00160     T4_LENGTH_1200_US_LETTER = 0,
00161     /* North American legal is 355.6mm long */
00162     T4_LENGTH_STANDARD_US_LEGAL = 1369,
00163     T4_LENGTH_FINE_US_LEGAL = 2738,
00164     T4_LENGTH_300_US_LEGAL = 0,
00165     T4_LENGTH_SUPERFINE_US_LEGAL = 5476,
00166     T4_LENGTH_600_US_LEGAL = 0,
00167     T4_LENGTH_800_US_LEGAL = 0,
00168     T4_LENGTH_1200_US_LEGAL = 0
00169 } t4_image_length_t;
00170 
00171 /*!
00172     T.4 FAX compression/decompression descriptor. This defines the working state
00173     for a single instance of a T.4 FAX compression or decompression channel.
00174 */
00175 typedef struct
00176 {
00177     /* "Background" information about the FAX, which can be stored in a TIFF file. */
00178     /*! \brief The vendor of the machine which produced the TIFF file. */ 
00179     const char *vendor;
00180     /*! \brief The model of machine which produced the TIFF file. */ 
00181     const char *model;
00182     /*! \brief The local ident string. */ 
00183     const char *local_ident;
00184     /*! \brief The remote end's ident string. */ 
00185     const char *far_ident;
00186     /*! \brief The FAX sub-address. */ 
00187     const char *sub_address;
00188     /*! \brief The FAX DCS information, as an ASCII string. */ 
00189     const char *dcs;
00190     /*! \brief The text which will be used in FAX page header. No text results
00191                in no header line. */
00192     const char *header_info;
00193 
00194     /*! \brief The type of compression used between the FAX machines. */
00195     int line_encoding;
00196     /*! \brief The minimum number of encoded bits per row. This is a timing thing
00197                for hardware FAX machines. */
00198     int min_row_bits;
00199     
00200     /*! \brief The compression type for output to the TIFF file. */
00201     int output_compression;
00202     /*! \brief The TIFF G3 FAX options. */
00203     int output_t4_options;
00204 
00205     /*! \brief The time at which handling of the current page began. */
00206     time_t page_start_time;
00207 
00208     /*! \brief The current number of bytes per row of uncompressed image data. */
00209     int bytes_per_row;
00210     /*! \brief The size of the image in the image buffer, in bytes. */
00211     int image_size;
00212     /*! \brief The current size of the image buffer. */
00213     int image_buffer_size;
00214     uint8_t *image_buffer;
00215 
00216     /*! \brief The libtiff context for the current TIFF file */
00217     TIFF *tiff_file;
00218     /*! \brief The current file name. */
00219     const char *file;
00220     /*! \brief The first page to transfer. -1 to start at the beginning of the file. */
00221     int start_page;
00222     /*! \brief The last page to transfer. -1 to continue to the end of the file. */
00223     int stop_page;
00224 
00225     /*! \brief The number of pages transferred to date. */
00226     int pages_transferred;
00227     /*! \brief The number of pages in the current TIFF file. */
00228     int pages_in_file;
00229     /*! \brief Column-to-column (X) resolution in pixels per metre. */
00230     int x_resolution;
00231     /*! \brief Row-to-row (Y) resolution in pixels per metre. */
00232     int y_resolution;
00233     /*! \brief Width of the current page, in pixels. */
00234     int image_width;
00235     /*! \brief Current pixel row number. */
00236     int row;
00237     /*! \brief Total pixel rows in the current page. */
00238     int image_length;
00239     /*! \brief The current number of consecutive bad rows. */
00240     int curr_bad_row_run;
00241     /*! \brief The longest run of consecutive bad rows seen in the current page. */
00242     int longest_bad_row_run;
00243     /*! \brief The total number of bad rows in the current page. */
00244     int bad_rows;
00245 
00246     uint32_t bits_to_date;
00247     int bits;
00248 
00249     /*! \brief This variable is set if we are treating the current row as a 2D encoded
00250                one. */
00251     int row_is_2d;
00252     /*! \brief TRUE if the current run is black */
00253     int its_black;
00254     /*! \brief The current length of the current row. */
00255     int row_len;
00256     /*! \brief This variable is used to record the fact we have seen at least one EOL
00257                since we started decoding. We will not try to interpret the received
00258                data as an image until we have seen the first EOL. */
00259     int first_eol_seen;
00260     /*! \brief This variable is used to count the consecutive EOLS we have seen. If it
00261                reaches six, this is the end of the image. */
00262     int consecutive_eols;
00263 
00264     /*! \brief Black and white run-lengths for the current row. */
00265     uint32_t *cur_runs;
00266     /*! \brief Black and white run-lengths for the reference row. */
00267     uint32_t *ref_runs;
00268     /*! \brief The number of runs currently in the reference row. */
00269     int ref_steps;
00270     /*! \brief The current step into the reference row run-lengths buffer. */
00271     int b_cursor;
00272     /*! \brief The current step into the current row run-lengths buffer. */
00273     int a_cursor;
00274 
00275     /*! \brief The reference or starting changing element on the coding line. At the
00276                start of the coding line, a0 is set on an imaginary white changing element
00277                situated just before the first element on the line. During the coding of
00278                the coding line, the position of a0 is defined by the previous coding mode.
00279                (See 4.2.1.3.2.). */
00280     int a0;
00281     /*! \brief The first changing element on the reference line to the right of a0 and of
00282                opposite colour to a0. */
00283     int b1;
00284     /*! \brief The length of the in-progress run of black or white. */
00285     int run_length;
00286     /*! \brief 2D horizontal mode control. */
00287     int black_white;
00288 
00289     uint32_t data;
00290     int data_bits;
00291 
00292     /*! \brief A pointer into the image buffer indicating where the last row begins */
00293     int last_row_starts_at;
00294     int row_starts_at;
00295     
00296     /*! \brief Pointer to the buffer for the current pixel row. */
00297     uint8_t *row_buf;
00298     
00299     int bit_pos;
00300     int bit_ptr;
00301 
00302     /*! \brief The maximum contiguous rows that will be 2D encoded. */
00303     int max_rows_to_next_1d_row;
00304     /*! \brief Number of rows left that can be 2D encoded, before a 1D encoded row
00305                must be used. */
00306     int rows_to_next_1d_row;
00307     /*! \brief The current number of bits in the current encoded row. */
00308     int row_bits;
00309 
00310     t4_row_read_handler_t row_read_handler;
00311     void *row_read_user_data;
00312     t4_row_write_handler_t row_write_handler;
00313     void *row_write_user_data;
00314 
00315     /*! \brief Error and flow logging control */
00316     logging_state_t logging;
00317 } t4_state_t;
00318 
00319 /*!
00320     T.4 FAX compression/decompression statistics.
00321 */
00322 typedef struct
00323 {
00324     /*! \brief The number of pages transferred so far. */
00325     int pages_transferred;
00326     /*! \brief The number of pages in the file (<0 if unknown). */
00327     int pages_in_file;
00328     /*! \brief The number of horizontal pixels in the most recent page. */
00329     int width;
00330     /*! \brief The number of vertical pixels in the most recent page. */
00331     int length;
00332     /*! \brief The number of bad pixel rows in the most recent page. */
00333     int bad_rows;
00334     /*! \brief The largest number of bad pixel rows in a block in the most recent page. */
00335     int longest_bad_row_run;
00336     /*! \brief The horizontal resolution of the page in pixels per metre */
00337     int x_resolution;
00338     /*! \brief The vertical resolution of the page in pixels per metre */
00339     int y_resolution;
00340     /*! \brief The type of compression used between the FAX machines */
00341     int encoding;
00342     /*! \brief The size of the image, in bytes */
00343     int image_size;
00344 } t4_stats_t;
00345     
00346 #if defined(__cplusplus)
00347 extern "C" {
00348 #endif
00349 
00350 /*! \brief Prepare for reception of a document.
00351     \param s The T.4 context.
00352     \param file The name of the file to be received.
00353     \param output_encoding The output encoding.
00354     \return A pointer to the context, or NULL if there was a problem. */
00355 t4_state_t *t4_rx_init(t4_state_t *s, const char *file, int output_encoding);
00356 
00357 /*! \brief Prepare to receive the next page of the current document.
00358     \param s The T.4 context.
00359     \return zero for success, -1 for failure. */
00360 int t4_rx_start_page(t4_state_t *s);
00361 
00362 /*! \brief Put a bit of the current document page.
00363     \param s The T.4 context.
00364     \param bit The data bit.
00365     \return TRUE when the bit ends the document page, otherwise FALSE. */
00366 int t4_rx_put_bit(t4_state_t *s, int bit);
00367 
00368 /*! \brief Put a byte of the current document page.
00369     \param s The T.4 context.
00370     \param byte The data byte.
00371     \return TRUE when the byte ends the document page, otherwise FALSE. */
00372 int t4_rx_put_byte(t4_state_t *s, uint8_t byte);
00373 
00374 /*! \brief Put a byte of the current document page.
00375     \param s The T.4 context.
00376     \param buf The buffer containing the chunk.
00377     \param len The length of the chunk.
00378     \return TRUE when the byte ends the document page, otherwise FALSE. */
00379 int t4_rx_put_chunk(t4_state_t *s, const uint8_t buf[], int len);
00380 
00381 /*! \brief Complete the reception of a page.
00382     \param s The T.4 receive context.
00383     \return 0 for success, otherwise -1. */
00384 int t4_rx_end_page(t4_state_t *s);
00385 
00386 /*! \brief End reception of a document. Tidy up, close the file and
00387            free the context. This should be used to end T.4 reception
00388            started with t4_rx_init.
00389     \param s The T.4 receive context.
00390     \return 0 for success, otherwise -1. */
00391 int t4_rx_delete(t4_state_t *s);
00392 
00393 /*! \brief End reception of a document. Tidy up and close the file.
00394            This should be used to end T.4 reception started with
00395            t4_rx_init.
00396     \param s The T.4 context.
00397     \return 0 for success, otherwise -1. */
00398 int t4_rx_end(t4_state_t *s);
00399 
00400 int t4_rx_set_row_write_handler(t4_state_t *s, t4_row_write_handler_t handler, void *user_data);
00401 
00402 /*! \brief Set the encoding for the received data.
00403     \param s The T.4 context.
00404     \param encoding The encoding. */
00405 void t4_rx_set_rx_encoding(t4_state_t *s, int encoding);
00406 
00407 /*! \brief Set the expected width of the received image, in pixel columns.
00408     \param s The T.4 context.
00409     \param columns The number of pixels across the image. */
00410 void t4_rx_set_image_width(t4_state_t *s, int width);
00411 
00412 /*! \brief Set the row-to-row (y) resolution to expect for a received image.
00413     \param s The T.4 context.
00414     \param resolution The resolution, in pixels per metre. */
00415 void t4_rx_set_y_resolution(t4_state_t *s, int resolution);
00416 
00417 /*! \brief Set the column-to-column (x) resolution to expect for a received image.
00418     \param s The T.4 context.
00419     \param resolution The resolution, in pixels per metre. */
00420 void t4_rx_set_x_resolution(t4_state_t *s, int resolution);
00421 
00422 /*! \brief Set the DCS information of the fax, for inclusion in the file.
00423     \param s The T.4 context.
00424     \param dcs The DCS information, formatted as an ASCII string. */
00425 void t4_rx_set_dcs(t4_state_t *s, const char *dcs);
00426 
00427 /*! \brief Set the sub-address of the fax, for inclusion in the file.
00428     \param s The T.4 context.
00429     \param sub_address The sub-address string. */
00430 void t4_rx_set_sub_address(t4_state_t *s, const char *sub_address);
00431 
00432 /*! \brief Set the identity of the remote machine, for inclusion in the file.
00433     \param s The T.4 context.
00434     \param ident The identity string. */
00435 void t4_rx_set_far_ident(t4_state_t *s, const char *ident);
00436 
00437 /*! \brief Set the vendor of the remote machine, for inclusion in the file.
00438     \param s The T.4 context.
00439     \param vendor The vendor string, or NULL. */
00440 void t4_rx_set_vendor(t4_state_t *s, const char *vendor);
00441 
00442 /*! \brief Set the model of the remote machine, for inclusion in the file.
00443     \param s The T.4 context.
00444     \param model The model string, or NULL. */
00445 void t4_rx_set_model(t4_state_t *s, const char *model);
00446 
00447 /*! \brief Prepare for transmission of a document.
00448     \param s The T.4 context.
00449     \param file The name of the file to be sent.
00450     \param start_page The first page to send. -1 for no restriction.
00451     \param stop_page The last page to send. -1 for no restriction.
00452     \return A pointer to the context, or NULL if there was a problem. */
00453 t4_state_t *t4_tx_init(t4_state_t *s, const char *file, int start_page, int stop_page);
00454 
00455 /*! \brief Prepare to send the next page of the current document.
00456     \param s The T.4 context.
00457     \return zero for success, -1 for failure. */
00458 int t4_tx_start_page(t4_state_t *s);
00459 
00460 /*! \brief Prepare the current page for a resend.
00461     \param s The T.4 context.
00462     \return zero for success, -1 for failure. */
00463 int t4_tx_restart_page(t4_state_t *s);
00464 
00465 /*! \brief Check for the existance of the next page. This information can
00466     be needed before it is determined that the current page is finished with.
00467     \param s The T.4 context.
00468     \return zero for next page found, -1 for failure. */
00469 int t4_tx_more_pages(t4_state_t *s);
00470 
00471 /*! \brief Complete the sending of a page.
00472     \param s The T.4 context.
00473     \return zero for success, -1 for failure. */
00474 int t4_tx_end_page(t4_state_t *s);
00475 
00476 /*! \brief Get the next bit of the current document page. The document will
00477            be padded for the current minimum scan line time. If the
00478            file does not contain an RTC (return to control) code at
00479            the end of the page, one will be added where appropriate.
00480     \param s The T.4 context.
00481     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00482             set (i.e. the returned value is 2 or 3). */
00483 int t4_tx_get_bit(t4_state_t *s);
00484 
00485 /*! \brief Get the next byte of the current document page. The document will
00486            be padded for the current minimum scan line time. If the
00487            file does not contain an RTC (return to control) code at
00488            the end of the page, one will be added where appropriate.
00489     \param s The T.4 context.
00490     \return The next byte. For the last byte of data, bit 8 is
00491             set. In this case, one or more bits of the byte may be padded with
00492             zeros, to complete the byte. */
00493 int t4_tx_get_byte(t4_state_t *s);
00494 
00495 /*! \brief Get the next chunk of the current document page. The document will
00496            be padded for the current minimum scan line time. If the
00497            file does not contain an RTC (return to control) code at
00498            the end of the page, one will be added where appropriate.
00499     \param s The T.4 context.
00500     \param buf The buffer into which the chunk is to written.
00501     \param max_len The maximum length of the chunk.
00502     \return The actual length of the chunk. If this is less than max_len it 
00503             indicates that the end of the document has been reached. */
00504 int t4_tx_get_chunk(t4_state_t *s, uint8_t buf[], int max_len);
00505 
00506 /*! \brief Return the next bit of the current document page, without actually
00507            moving forward in the buffer. The document will be padded for the
00508            current minimum scan line time. If the file does not contain an
00509            RTC (return to control) code at the end of the page, one will be
00510            added.
00511     \param s The T.4 context.
00512     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00513             set (i.e. the returned value is 2 or 3). */
00514 int t4_tx_check_bit(t4_state_t *s);
00515 
00516 /*! \brief End the transmission of a document. Tidy up, close the file and
00517            free the context. This should be used to end T.4 transmission
00518            started with t4_tx_init.
00519     \param s The T.4 context.
00520     \return 0 for success, otherwise -1. */
00521 int t4_tx_delete(t4_state_t *s);
00522 
00523 /*! \brief End the transmission of a document. Tidy up and close the file.
00524            This should be used to end T.4 transmission started with t4_tx_init.
00525     \param s The T.4 context.
00526     \return 0 for success, otherwise -1. */
00527 int t4_tx_end(t4_state_t *s);
00528 
00529 /*! \brief Set the encoding for the encoded data.
00530     \param s The T.4 context.
00531     \param encoding The encoding. */
00532 void t4_tx_set_tx_encoding(t4_state_t *s, int encoding);
00533 
00534 /*! \brief Set the minimum number of encoded bits per row. This allows the
00535            makes the encoding process to be set to comply with the minimum row
00536            time specified by a remote receiving machine.
00537     \param s The T.4 context.
00538     \param bits The minimum number of bits per row. */
00539 void t4_tx_set_min_row_bits(t4_state_t *s, int bits);
00540 
00541 /*! \brief Set the identity of the local machine, for inclusion in page headers.
00542     \param s The T.4 context.
00543     \param ident The identity string. */
00544 void t4_tx_set_local_ident(t4_state_t *s, const char *ident);
00545 
00546 /*! Set the info field, included in the header line included in each page of an encoded
00547     FAX. This is a string of up to 50 characters. Other information (date, local ident, etc.)
00548     are automatically included in the header. If the header info is set to NULL or a zero
00549     length string, no header lines will be added to the encoded FAX.
00550     \brief Set the header info.
00551     \param s The T.4 context.
00552     \param info A string, of up to 50 bytes, which will form the info field. */
00553 void t4_tx_set_header_info(t4_state_t *s, const char *info);
00554 
00555 int t4_tx_set_row_read_handler(t4_state_t *s, t4_row_read_handler_t handler, void *user_data);
00556 
00557 /*! \brief Get the row-to-row (y) resolution of the current page.
00558     \param s The T.4 context.
00559     \return The resolution, in pixels per metre. */
00560 int t4_tx_get_y_resolution(t4_state_t *s);
00561 
00562 /*! \brief Get the column-to-column (x) resolution of the current page.
00563     \param s The T.4 context.
00564     \return The resolution, in pixels per metre. */
00565 int t4_tx_get_x_resolution(t4_state_t *s);
00566 
00567 /*! \brief Get the width of the current page, in pixel columns.
00568     \param s The T.4 context.
00569     \return The number of columns. */
00570 int t4_tx_get_image_width(t4_state_t *s);
00571 
00572 /*! \brief Get the number of pages in the file.
00573     \param s The T.4 context.
00574     \return The number of pages, or -1 if there is an error. */
00575 int t4_tx_get_pages_in_file(t4_state_t *s);
00576 
00577 /*! Get the current image transfer statistics. 
00578     \brief Get the current transfer statistics.
00579     \param s The T.4 context.
00580     \param t A pointer to a statistics structure. */
00581 void t4_get_transfer_statistics(t4_state_t *s, t4_stats_t *t);
00582 
00583 /*! Get the short text name of an encoding format. 
00584     \brief Get the short text name of an encoding format.
00585     \param encoding The encoding type.
00586     \return A pointer to the string. */
00587 const char *t4_encoding_to_str(int encoding);
00588 
00589 #if defined(__cplusplus)
00590 }
00591 #endif
00592 
00593 #endif
00594 /*- End of file ------------------------------------------------------------*/

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