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 1.47 2007/12/14 13:27:30 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 /*! Supported compression modes. */
00048 typedef enum
00049 {
00050     T4_COMPRESSION_ITU_T4_1D = 1,
00051     T4_COMPRESSION_ITU_T4_2D = 2,
00052     T4_COMPRESSION_ITU_T6 = 3
00053 } t4_image_compression_t;
00054 
00055 /*! Supported X resolutions, in pixels per metre. */
00056 typedef enum
00057 {
00058     T4_X_RESOLUTION_R4 = 4016,
00059     T4_X_RESOLUTION_R8 = 8031,
00060     T4_X_RESOLUTION_300 = 11811,
00061     T4_X_RESOLUTION_R16 = 16063,
00062     T4_X_RESOLUTION_600 = 23622,
00063     T4_X_RESOLUTION_800 = 31496,
00064     T4_X_RESOLUTION_1200 = 47244
00065 } t4_image_x_resolution_t;
00066 
00067 /*! Supported Y resolutions, in pixels per metre. */
00068 typedef enum
00069 {
00070     T4_Y_RESOLUTION_STANDARD = 3850,
00071     T4_Y_RESOLUTION_FINE = 7700,
00072     T4_Y_RESOLUTION_300 = 11811,
00073     T4_Y_RESOLUTION_SUPERFINE = 15400,  /* 400 is 15748 */
00074     T4_Y_RESOLUTION_600 = 23622,
00075     T4_Y_RESOLUTION_800 = 31496,
00076     T4_Y_RESOLUTION_1200 = 47244
00077 } t4_image_y_resolution_t;
00078 
00079 /*!
00080     Exact widths in PELs for the difference resolutions, and page widths.
00081     Note:
00082         The A4 widths also apply to North American letter and legal.
00083         The R4 resolution widths are not supported in recent versions of T.30
00084         Only images of exactly these widths are acceptable for FAX transmisson.
00085 
00086     R4    864 pels/215mm for ISO A4, North American Letter and Legal
00087     R4   1024 pels/255mm for ISO B4
00088     R4   1216 pels/303mm for ISO A3
00089     R8   1728 pels/215mm for ISO A4, North American Letter and Legal
00090     R8   2048 pels/255mm for ISO B4
00091     R8   2432 pels/303mm for ISO A3
00092     R16  3456 pels/215mm for ISO A4, North American Letter and Legal
00093     R16  4096 pels/255mm for ISO B4
00094     R16  4864 pels/303mm for ISO A3
00095 */
00096 typedef enum
00097 {
00098     T4_WIDTH_R4_A4 = 864,
00099     T4_WIDTH_R4_B4 = 1024,
00100     T4_WIDTH_R4_A3 = 1216,
00101     T4_WIDTH_R8_A4 = 1728,
00102     T4_WIDTH_R8_B4 = 2048,
00103     T4_WIDTH_R8_A3 = 2432,
00104     T4_WIDTH_300_A4 = 2592,
00105     T4_WIDTH_300_B4 = 3072,
00106     T4_WIDTH_300_A3 = 3648,
00107     T4_WIDTH_R16_A4 = 3456,
00108     T4_WIDTH_R16_B4 = 4096,
00109     T4_WIDTH_R16_A3 = 4864,
00110     T4_WIDTH_600_A4 = 5184,
00111     T4_WIDTH_600_B4 = 6144,
00112     T4_WIDTH_600_A3 = 7296,
00113     T4_WIDTH_1200_A4 = 10368,
00114     T4_WIDTH_1200_B4 = 12288,
00115     T4_WIDTH_1200_A3 = 14592
00116 } t4_image_width_t;
00117 
00118 /*!
00119     Length of the various supported paper sizes, in pixels at the various Y resolutions.
00120     Paper sizes are
00121         A4 (215mm x 297mm)
00122         B4 (255mm x 364mm)
00123         A3 (303mm x 418.56mm)
00124         North American Letter (215.9mm x 279.4mm)
00125         North American Legal (215.9mm x 355.6mm)
00126         Unlimited
00127 
00128     T.4 does not accurately define the maximum number of scan lines in a page. A wide
00129     variety of maximum row counts are used in the real world. It is important not to
00130     set our sending limit too high, or a receiving machine might split pages. It is
00131     important not to set it too low, or we might clip pages.
00132 
00133     Values seen for standard resolution A4 pages include 1037, 1045, 1109, 1126 and 1143.
00134     1109 seems the most-popular.  At fine res 2150, 2196, 2200, 2237, 2252-2262, 2264,
00135     2286, and 2394 are used. 2255 seems the most popular. We try to use balanced choices
00136     here.
00137 */
00138 typedef enum
00139 {
00140     /* A4 is 297mm long */
00141     T4_LENGTH_STANDARD_A4 = 1143,
00142     T4_LENGTH_FINE_A4 = 2286,
00143     T4_LENGTH_300_A4 = 4665,
00144     T4_LENGTH_SUPERFINE_A4 = 4573,
00145     T4_LENGTH_600_A4 = 6998,
00146     T4_LENGTH_800_A4 = 9330,
00147     T4_LENGTH_1200_A4 = 13996,
00148     /* B4 is 364mm long */
00149     T4_LENGTH_STANDARD_B4 = 1401,
00150     T4_LENGTH_FINE_B4 = 2802,
00151     T4_LENGTH_300_B4 = 0,
00152     T4_LENGTH_SUPERFINE_B4 = 5605,
00153     T4_LENGTH_600_B4 = 0,
00154     T4_LENGTH_800_B4 = 0,
00155     T4_LENGTH_1200_B4 = 0,
00156     /* North American letter is 279.4mm long */
00157     T4_LENGTH_STANDARD_US_LETTER = 1075,
00158     T4_LENGTH_FINE_US_LETTER = 2151,
00159     T4_LENGTH_300_US_LETTER = 0,
00160     T4_LENGTH_SUPERFINE_US_LETTER = 4302,
00161     T4_LENGTH_600_US_LETTER = 0,
00162     T4_LENGTH_800_US_LETTER = 0,
00163     T4_LENGTH_1200_US_LETTER = 0,
00164     /* North American legal is 355.6mm long */
00165     T4_LENGTH_STANDARD_US_LEGAL = 1369,
00166     T4_LENGTH_FINE_US_LEGAL = 2738,
00167     T4_LENGTH_300_US_LEGAL = 0,
00168     T4_LENGTH_SUPERFINE_US_LEGAL = 5476,
00169     T4_LENGTH_600_US_LEGAL = 0,
00170     T4_LENGTH_800_US_LEGAL = 0,
00171     T4_LENGTH_1200_US_LEGAL = 0
00172 } t4_image_length_t;
00173 
00174 /*!
00175     T.4 FAX compression/decompression descriptor. This defines the working state
00176     for a single instance of a T.4 FAX compression or decompression channel.
00177 */
00178 typedef struct
00179 {
00180     /* "Background" information about the FAX, which can be stored in a TIFF file. */
00181     /*! \brief The vendor of the machine which produced the TIFF file. */ 
00182     const char *vendor;
00183     /*! \brief The model of machine which produced the TIFF file. */ 
00184     const char *model;
00185     /*! \brief The local ident string. */ 
00186     const char *local_ident;
00187     /*! \brief The remote end's ident string. */ 
00188     const char *far_ident;
00189     /*! \brief The FAX sub-address. */ 
00190     const char *sub_address;
00191     /*! \brief The FAX DCS information, as an ASCII string. */ 
00192     const char *dcs;
00193     /*! \brief The text which will be used in FAX page header. No text results
00194                in no header line. */
00195     const char *header_info;
00196 
00197     /*! \brief The type of compression used between the FAX machines. */
00198     int line_encoding;
00199     /*! \brief The minimum number of encoded bits per row. This is a timing thing
00200                for hardware FAX machines. */
00201     int min_bits_per_row;
00202     
00203     /*! \brief The compression type for output to the TIFF file. */
00204     int output_compression;
00205     /*! \brief The TIFF G3 FAX options. */
00206     int output_t4_options;
00207 
00208     /*! \brief Callback function to read a row of pixels from the image source. */
00209     t4_row_read_handler_t row_read_handler;
00210     /*! \brief Opaque pointer passed to row_read_handler. */
00211     void *row_read_user_data;
00212     /*! \brief Callback function to write a row of pixels to the image destination. */
00213     t4_row_write_handler_t row_write_handler;
00214     /*! \brief Opaque pointer passed to row_write_handler. */
00215     void *row_write_user_data;
00216 
00217     /*! \brief The time at which handling of the current page began. */
00218     time_t page_start_time;
00219 
00220     /*! \brief The current number of bytes per row of uncompressed image data. */
00221     int bytes_per_row;
00222     /*! \brief The size of the image in the image buffer, in bytes. */
00223     int image_size;
00224     /*! \brief The current size of the image buffer. */
00225     int image_buffer_size;
00226     /*! \brief A point to the image buffer. */
00227     uint8_t *image_buffer;
00228 
00229     /*! \brief The libtiff context for the current TIFF file */
00230     TIFF *tiff_file;
00231     /*! \brief The current file name. */
00232     const char *file;
00233     /*! \brief The first page to transfer. -1 to start at the beginning of the file. */
00234     int start_page;
00235     /*! \brief The last page to transfer. -1 to continue to the end of the file. */
00236     int stop_page;
00237 
00238     /*! \brief The number of pages transferred to date. */
00239     int pages_transferred;
00240     /*! \brief The number of pages in the current TIFF file. */
00241     int pages_in_file;
00242     /*! \brief Column-to-column (X) resolution in pixels per metre. */
00243     int x_resolution;
00244     /*! \brief Row-to-row (Y) resolution in pixels per metre. */
00245     int y_resolution;
00246     /*! \brief Width of the current page, in pixels. */
00247     int image_width;
00248     /*! \brief Length of the current page, in pixels. */
00249     int image_length;
00250     /*! \brief Current pixel row number. */
00251     int row;
00252     /*! \brief The current number of consecutive bad rows. */
00253     int curr_bad_row_run;
00254     /*! \brief The longest run of consecutive bad rows seen in the current page. */
00255     int longest_bad_row_run;
00256     /*! \brief The total number of bad rows in the current page. */
00257     int bad_rows;
00258 
00259     /*! \brief Incoming bit buffer for decompression. */
00260     uint32_t rx_bitstream;
00261     /*! \brief The number of bits currently in rx_bitstream. */
00262     int rx_bits;
00263 
00264     /*! \brief This variable is set if we are treating the current row as a 2D encoded
00265                one. */
00266     int row_is_2d;
00267     /*! \brief TRUE if the current run is black */
00268     int its_black;
00269     /*! \brief The current length of the current row. */
00270     int row_len;
00271     /*! \brief This variable is used to record the fact we have seen at least one EOL
00272                since we started decoding. We will not try to interpret the received
00273                data as an image until we have seen the first EOL. */
00274     int first_eol_seen;
00275     /*! \brief This variable is used to count the consecutive EOLS we have seen. If it
00276                reaches six, this is the end of the image. */
00277     int consecutive_eols;
00278 
00279     /*! \brief Black and white run-lengths for the current row. */
00280     uint32_t *cur_runs;
00281     /*! \brief Black and white run-lengths for the reference row. */
00282     uint32_t *ref_runs;
00283     /*! \brief The number of runs currently in the reference row. */
00284     int ref_steps;
00285     /*! \brief The current step into the reference row run-lengths buffer. */
00286     int b_cursor;
00287     /*! \brief The current step into the current row run-lengths buffer. */
00288     int a_cursor;
00289 
00290     /*! \brief The reference or starting changing element on the coding line. At the
00291                start of the coding line, a0 is set on an imaginary white changing element
00292                situated just before the first element on the line. During the coding of
00293                the coding line, the position of a0 is defined by the previous coding mode.
00294                (See 4.2.1.3.2.). */
00295     int a0;
00296     /*! \brief The first changing element on the reference line to the right of a0 and of
00297                opposite colour to a0. */
00298     int b1;
00299     /*! \brief The length of the in-progress run of black or white. */
00300     int run_length;
00301     /*! \brief 2D horizontal mode control. */
00302     int black_white;
00303 
00304     /*! \brief Encoded data bits buffer. */
00305     uint32_t tx_bitstream;
00306     /*! \brief The number of bits currently in tx_bitstream. */
00307     int tx_bits;
00308 
00309     /*! \brief A pointer into the image buffer indicating where the last row begins */
00310     int last_row_starts_at;
00311     /*! \brief A pointer into the image buffer indicating where the current row begins */
00312     int row_starts_at;
00313     
00314     /*! \brief Pointer to the buffer for the current pixel row. */
00315     uint8_t *row_buf;
00316     
00317     /*! \brief Pointer to the byte containing the next image bit to transmit. */
00318     int bit_pos;
00319     /*! \brief Pointer to the bit within the byte containing the next image bit to transmit. */
00320     int bit_ptr;
00321 
00322     /*! \brief The current maximum contiguous rows that may be 2D encoded. */
00323     int max_rows_to_next_1d_row;
00324     /*! \brief Number of rows left that can be 2D encoded, before a 1D encoded row
00325                must be used. */
00326     int rows_to_next_1d_row;
00327     /*! \brief The current number of bits in the current encoded row. */
00328     int row_bits;
00329     /*! \brief The minimum bits in any row of the current page. For monitoring only. */
00330     int min_row_bits;
00331     /*! \brief The maximum bits in any row of the current page. For monitoring only. */
00332     int max_row_bits;
00333 
00334     /*! \brief Error and flow logging control */
00335     logging_state_t logging;
00336 } t4_state_t;
00337 
00338 /*!
00339     T.4 FAX compression/decompression statistics.
00340 */
00341 typedef struct
00342 {
00343     /*! \brief The number of pages transferred so far. */
00344     int pages_transferred;
00345     /*! \brief The number of pages in the file (<0 if unknown). */
00346     int pages_in_file;
00347     /*! \brief The number of horizontal pixels in the most recent page. */
00348     int width;
00349     /*! \brief The number of vertical pixels in the most recent page. */
00350     int length;
00351     /*! \brief The number of bad pixel rows in the most recent page. */
00352     int bad_rows;
00353     /*! \brief The largest number of bad pixel rows in a block in the most recent page. */
00354     int longest_bad_row_run;
00355     /*! \brief The horizontal resolution of the page in pixels per metre */
00356     int x_resolution;
00357     /*! \brief The vertical resolution of the page in pixels per metre */
00358     int y_resolution;
00359     /*! \brief The type of compression used between the FAX machines */
00360     int encoding;
00361     /*! \brief The size of the image, in bytes */
00362     int image_size;
00363 } t4_stats_t;
00364     
00365 #if defined(__cplusplus)
00366 extern "C" {
00367 #endif
00368 
00369 /*! \brief Prepare for reception of a document.
00370     \param s The T.4 context.
00371     \param file The name of the file to be received.
00372     \param output_encoding The output encoding.
00373     \return A pointer to the context, or NULL if there was a problem. */
00374 t4_state_t *t4_rx_init(t4_state_t *s, const char *file, int output_encoding);
00375 
00376 /*! \brief Prepare to receive the next page of the current document.
00377     \param s The T.4 context.
00378     \return zero for success, -1 for failure. */
00379 int t4_rx_start_page(t4_state_t *s);
00380 
00381 /*! \brief Put a bit of the current document page.
00382     \param s The T.4 context.
00383     \param bit The data bit.
00384     \return TRUE when the bit ends the document page, otherwise FALSE. */
00385 int t4_rx_put_bit(t4_state_t *s, int bit);
00386 
00387 /*! \brief Put a byte of the current document page.
00388     \param s The T.4 context.
00389     \param byte The data byte.
00390     \return TRUE when the byte ends the document page, otherwise FALSE. */
00391 int t4_rx_put_byte(t4_state_t *s, uint8_t byte);
00392 
00393 /*! \brief Put a byte of the current document page.
00394     \param s The T.4 context.
00395     \param buf The buffer containing the chunk.
00396     \param len The length of the chunk.
00397     \return TRUE when the byte ends the document page, otherwise FALSE. */
00398 int t4_rx_put_chunk(t4_state_t *s, const uint8_t buf[], int len);
00399 
00400 /*! \brief Complete the reception of a page.
00401     \param s The T.4 receive context.
00402     \return 0 for success, otherwise -1. */
00403 int t4_rx_end_page(t4_state_t *s);
00404 
00405 /*! \brief End reception of a document. Tidy up, close the file and
00406            free the context. This should be used to end T.4 reception
00407            started with t4_rx_init.
00408     \param s The T.4 receive context.
00409     \return 0 for success, otherwise -1. */
00410 int t4_rx_delete(t4_state_t *s);
00411 
00412 /*! \brief End reception of a document. Tidy up and close the file.
00413            This should be used to end T.4 reception started with
00414            t4_rx_init.
00415     \param s The T.4 context.
00416     \return 0 for success, otherwise -1. */
00417 int t4_rx_end(t4_state_t *s);
00418 
00419 int t4_rx_set_row_write_handler(t4_state_t *s, t4_row_write_handler_t handler, void *user_data);
00420 
00421 /*! \brief Set the encoding for the received data.
00422     \param s The T.4 context.
00423     \param encoding The encoding. */
00424 void t4_rx_set_rx_encoding(t4_state_t *s, int encoding);
00425 
00426 /*! \brief Set the expected width of the received image, in pixel columns.
00427     \param s The T.4 context.
00428     \param width The number of pixels across the image. */
00429 void t4_rx_set_image_width(t4_state_t *s, int width);
00430 
00431 /*! \brief Set the row-to-row (y) resolution to expect for a received image.
00432     \param s The T.4 context.
00433     \param resolution The resolution, in pixels per metre. */
00434 void t4_rx_set_y_resolution(t4_state_t *s, int resolution);
00435 
00436 /*! \brief Set the column-to-column (x) resolution to expect for a received image.
00437     \param s The T.4 context.
00438     \param resolution The resolution, in pixels per metre. */
00439 void t4_rx_set_x_resolution(t4_state_t *s, int resolution);
00440 
00441 /*! \brief Set the DCS information of the fax, for inclusion in the file.
00442     \param s The T.4 context.
00443     \param dcs The DCS information, formatted as an ASCII string. */
00444 void t4_rx_set_dcs(t4_state_t *s, const char *dcs);
00445 
00446 /*! \brief Set the sub-address of the fax, for inclusion in the file.
00447     \param s The T.4 context.
00448     \param sub_address The sub-address string. */
00449 void t4_rx_set_sub_address(t4_state_t *s, const char *sub_address);
00450 
00451 /*! \brief Set the identity of the remote machine, for inclusion in the file.
00452     \param s The T.4 context.
00453     \param ident The identity string. */
00454 void t4_rx_set_far_ident(t4_state_t *s, const char *ident);
00455 
00456 /*! \brief Set the vendor of the remote machine, for inclusion in the file.
00457     \param s The T.4 context.
00458     \param vendor The vendor string, or NULL. */
00459 void t4_rx_set_vendor(t4_state_t *s, const char *vendor);
00460 
00461 /*! \brief Set the model of the remote machine, for inclusion in the file.
00462     \param s The T.4 context.
00463     \param model The model string, or NULL. */
00464 void t4_rx_set_model(t4_state_t *s, const char *model);
00465 
00466 /*! \brief Prepare for transmission of a document.
00467     \param s The T.4 context.
00468     \param file The name of the file to be sent.
00469     \param start_page The first page to send. -1 for no restriction.
00470     \param stop_page The last page to send. -1 for no restriction.
00471     \return A pointer to the context, or NULL if there was a problem. */
00472 t4_state_t *t4_tx_init(t4_state_t *s, const char *file, int start_page, int stop_page);
00473 
00474 /*! \brief Prepare to send the next page of the current document.
00475     \param s The T.4 context.
00476     \return zero for success, -1 for failure. */
00477 int t4_tx_start_page(t4_state_t *s);
00478 
00479 /*! \brief Prepare the current page for a resend.
00480     \param s The T.4 context.
00481     \return zero for success, -1 for failure. */
00482 int t4_tx_restart_page(t4_state_t *s);
00483 
00484 /*! \brief Check for the existance of the next page. This information can
00485     be needed before it is determined that the current page is finished with.
00486     \param s The T.4 context.
00487     \return zero for next page found, -1 for failure. */
00488 int t4_tx_more_pages(t4_state_t *s);
00489 
00490 /*! \brief Complete the sending of a page.
00491     \param s The T.4 context.
00492     \return zero for success, -1 for failure. */
00493 int t4_tx_end_page(t4_state_t *s);
00494 
00495 /*! \brief Get the next bit 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     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00501             set (i.e. the returned value is 2 or 3). */
00502 int t4_tx_get_bit(t4_state_t *s);
00503 
00504 /*! \brief Get the next byte of the current document page. The document will
00505            be padded for the current minimum scan line time. If the
00506            file does not contain an RTC (return to control) code at
00507            the end of the page, one will be added where appropriate.
00508     \param s The T.4 context.
00509     \return The next byte. For the last byte of data, bit 8 is
00510             set. In this case, one or more bits of the byte may be padded with
00511             zeros, to complete the byte. */
00512 int t4_tx_get_byte(t4_state_t *s);
00513 
00514 /*! \brief Get the next chunk of the current document page. The document will
00515            be padded for the current minimum scan line time. If the
00516            file does not contain an RTC (return to control) code at
00517            the end of the page, one will be added where appropriate.
00518     \param s The T.4 context.
00519     \param buf The buffer into which the chunk is to written.
00520     \param max_len The maximum length of the chunk.
00521     \return The actual length of the chunk. If this is less than max_len it 
00522             indicates that the end of the document has been reached. */
00523 int t4_tx_get_chunk(t4_state_t *s, uint8_t buf[], int max_len);
00524 
00525 /*! \brief Return the next bit of the current document page, without actually
00526            moving forward in the buffer. The document will be padded for the
00527            current minimum scan line time. If the file does not contain an
00528            RTC (return to control) code at the end of the page, one will be
00529            added.
00530     \param s The T.4 context.
00531     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00532             set (i.e. the returned value is 2 or 3). */
00533 int t4_tx_check_bit(t4_state_t *s);
00534 
00535 /*! \brief End the transmission of a document. Tidy up, close the file and
00536            free the context. This should be used to end T.4 transmission
00537            started with t4_tx_init.
00538     \param s The T.4 context.
00539     \return 0 for success, otherwise -1. */
00540 int t4_tx_delete(t4_state_t *s);
00541 
00542 /*! \brief End the transmission of a document. Tidy up and close the file.
00543            This should be used to end T.4 transmission started with t4_tx_init.
00544     \param s The T.4 context.
00545     \return 0 for success, otherwise -1. */
00546 int t4_tx_end(t4_state_t *s);
00547 
00548 /*! \brief Set the encoding for the encoded data.
00549     \param s The T.4 context.
00550     \param encoding The encoding. */
00551 void t4_tx_set_tx_encoding(t4_state_t *s, int encoding);
00552 
00553 /*! \brief Set the minimum number of encoded bits per row. This allows the
00554            makes the encoding process to be set to comply with the minimum row
00555            time specified by a remote receiving machine.
00556     \param s The T.4 context.
00557     \param bits The minimum number of bits per row. */
00558 void t4_tx_set_min_row_bits(t4_state_t *s, int bits);
00559 
00560 /*! \brief Set the identity of the local machine, for inclusion in page headers.
00561     \param s The T.4 context.
00562     \param ident The identity string. */
00563 void t4_tx_set_local_ident(t4_state_t *s, const char *ident);
00564 
00565 /*! Set the info field, included in the header line included in each page of an encoded
00566     FAX. This is a string of up to 50 characters. Other information (date, local ident, etc.)
00567     are automatically included in the header. If the header info is set to NULL or a zero
00568     length string, no header lines will be added to the encoded FAX.
00569     \brief Set the header info.
00570     \param s The T.4 context.
00571     \param info A string, of up to 50 bytes, which will form the info field. */
00572 void t4_tx_set_header_info(t4_state_t *s, const char *info);
00573 
00574 int t4_tx_set_row_read_handler(t4_state_t *s, t4_row_read_handler_t handler, void *user_data);
00575 
00576 /*! \brief Get the row-to-row (y) resolution of the current page.
00577     \param s The T.4 context.
00578     \return The resolution, in pixels per metre. */
00579 int t4_tx_get_y_resolution(t4_state_t *s);
00580 
00581 /*! \brief Get the column-to-column (x) resolution of the current page.
00582     \param s The T.4 context.
00583     \return The resolution, in pixels per metre. */
00584 int t4_tx_get_x_resolution(t4_state_t *s);
00585 
00586 /*! \brief Get the width of the current page, in pixel columns.
00587     \param s The T.4 context.
00588     \return The number of columns. */
00589 int t4_tx_get_image_width(t4_state_t *s);
00590 
00591 /*! \brief Get the number of pages in the file.
00592     \param s The T.4 context.
00593     \return The number of pages, or -1 if there is an error. */
00594 int t4_tx_get_pages_in_file(t4_state_t *s);
00595 
00596 /*! Get the current image transfer statistics. 
00597     \brief Get the current transfer statistics.
00598     \param s The T.4 context.
00599     \param t A pointer to a statistics structure. */
00600 void t4_get_transfer_statistics(t4_state_t *s, t4_stats_t *t);
00601 
00602 /*! Get the short text name of an encoding format. 
00603     \brief Get the short text name of an encoding format.
00604     \param encoding The encoding type.
00605     \return A pointer to the string. */
00606 const char *t4_encoding_to_str(int encoding);
00607 
00608 #if defined(__cplusplus)
00609 }
00610 #endif
00611 
00612 #endif
00613 /*- End of file ------------------------------------------------------------*/

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