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 Lesser General Public License version 2.1, 00014 * as 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 Lesser General Public License for more details. 00020 * 00021 * You should have received a copy of the GNU Lesser General Public 00022 * License 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 1.59 2009/04/12 09:12:10 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 t4_state_s t4_state_t; 00179 00180 /*! 00181 T.4 FAX compression/decompression statistics. 00182 */ 00183 typedef struct 00184 { 00185 /*! \brief The number of pages transferred so far. */ 00186 int pages_transferred; 00187 /*! \brief The number of pages in the file (<0 if unknown). */ 00188 int pages_in_file; 00189 /*! \brief The number of horizontal pixels in the most recent page. */ 00190 int width; 00191 /*! \brief The number of vertical pixels in the most recent page. */ 00192 int length; 00193 /*! \brief The number of bad pixel rows in the most recent page. */ 00194 int bad_rows; 00195 /*! \brief The largest number of bad pixel rows in a block in the most recent page. */ 00196 int longest_bad_row_run; 00197 /*! \brief The horizontal resolution of the page in pixels per metre */ 00198 int x_resolution; 00199 /*! \brief The vertical resolution of the page in pixels per metre */ 00200 int y_resolution; 00201 /*! \brief The type of compression used between the FAX machines */ 00202 int encoding; 00203 /*! \brief The size of the image on the line, in bytes */ 00204 int line_image_size; 00205 } t4_stats_t; 00206 00207 #if defined(__cplusplus) 00208 extern "C" { 00209 #endif 00210 00211 /*! \brief Prepare for reception of a document. 00212 \param s The T.4 context. 00213 \param file The name of the file to be received. 00214 \param output_encoding The output encoding. 00215 \return A pointer to the context, or NULL if there was a problem. */ 00216 SPAN_DECLARE(t4_state_t *) t4_rx_init(t4_state_t *s, const char *file, int output_encoding); 00217 00218 /*! \brief Prepare to receive the next page of the current document. 00219 \param s The T.4 context. 00220 \return zero for success, -1 for failure. */ 00221 SPAN_DECLARE(int) t4_rx_start_page(t4_state_t *s); 00222 00223 /*! \brief Put a bit of the current document page. 00224 \param s The T.4 context. 00225 \param bit The data bit. 00226 \return TRUE when the bit ends the document page, otherwise FALSE. */ 00227 SPAN_DECLARE(int) t4_rx_put_bit(t4_state_t *s, int bit); 00228 00229 /*! \brief Put a byte of the current document page. 00230 \param s The T.4 context. 00231 \param byte The data byte. 00232 \return TRUE when the byte ends the document page, otherwise FALSE. */ 00233 SPAN_DECLARE(int) t4_rx_put_byte(t4_state_t *s, uint8_t byte); 00234 00235 /*! \brief Put a byte of the current document page. 00236 \param s The T.4 context. 00237 \param buf The buffer containing the chunk. 00238 \param len The length of the chunk. 00239 \return TRUE when the byte ends the document page, otherwise FALSE. */ 00240 SPAN_DECLARE(int) t4_rx_put_chunk(t4_state_t *s, const uint8_t buf[], int len); 00241 00242 /*! \brief Complete the reception of a page. 00243 \param s The T.4 receive context. 00244 \return 0 for success, otherwise -1. */ 00245 SPAN_DECLARE(int) t4_rx_end_page(t4_state_t *s); 00246 00247 /*! \brief End reception of a document. Tidy up and close the file. 00248 This should be used to end T.4 reception started with 00249 t4_rx_init. 00250 \param s The T.4 receive context. 00251 \return 0 for success, otherwise -1. */ 00252 SPAN_DECLARE(int) t4_rx_release(t4_state_t *s); 00253 00254 /*! \brief End reception of a document. Tidy up, close the file and 00255 free the context. This should be used to end T.4 reception 00256 started with t4_rx_init. 00257 \param s The T.4 receive context. 00258 \return 0 for success, otherwise -1. */ 00259 SPAN_DECLARE(int) t4_rx_free(t4_state_t *s); 00260 00261 /*! \brief Set the row write handler for a T.4 receive context. 00262 \param s The T.4 receive context. 00263 \param handler A pointer to the handler routine. 00264 \param user_data An opaque pointer passed to the handler routine. 00265 \return 0 for success, otherwise -1. */ 00266 SPAN_DECLARE(int) t4_rx_set_row_write_handler(t4_state_t *s, t4_row_write_handler_t handler, void *user_data); 00267 00268 /*! \brief Set the encoding for the received data. 00269 \param s The T.4 context. 00270 \param encoding The encoding. */ 00271 SPAN_DECLARE(void) t4_rx_set_rx_encoding(t4_state_t *s, int encoding); 00272 00273 /*! \brief Set the expected width of the received image, in pixel columns. 00274 \param s The T.4 context. 00275 \param width The number of pixels across the image. */ 00276 SPAN_DECLARE(void) t4_rx_set_image_width(t4_state_t *s, int width); 00277 00278 /*! \brief Set the row-to-row (y) resolution to expect for a received image. 00279 \param s The T.4 context. 00280 \param resolution The resolution, in pixels per metre. */ 00281 SPAN_DECLARE(void) t4_rx_set_y_resolution(t4_state_t *s, int resolution); 00282 00283 /*! \brief Set the column-to-column (x) resolution to expect for a received image. 00284 \param s The T.4 context. 00285 \param resolution The resolution, in pixels per metre. */ 00286 SPAN_DECLARE(void) t4_rx_set_x_resolution(t4_state_t *s, int resolution); 00287 00288 /*! \brief Set the DCS information of the fax, for inclusion in the file. 00289 \param s The T.4 context. 00290 \param dcs The DCS information, formatted as an ASCII string. */ 00291 SPAN_DECLARE(void) t4_rx_set_dcs(t4_state_t *s, const char *dcs); 00292 00293 /*! \brief Set the sub-address of the fax, for inclusion in the file. 00294 \param s The T.4 context. 00295 \param sub_address The sub-address string. */ 00296 SPAN_DECLARE(void) t4_rx_set_sub_address(t4_state_t *s, const char *sub_address); 00297 00298 /*! \brief Set the identity of the remote machine, for inclusion in the file. 00299 \param s The T.4 context. 00300 \param ident The identity string. */ 00301 SPAN_DECLARE(void) t4_rx_set_far_ident(t4_state_t *s, const char *ident); 00302 00303 /*! \brief Set the vendor of the remote machine, for inclusion in the file. 00304 \param s The T.4 context. 00305 \param vendor The vendor string, or NULL. */ 00306 SPAN_DECLARE(void) t4_rx_set_vendor(t4_state_t *s, const char *vendor); 00307 00308 /*! \brief Set the model of the remote machine, for inclusion in the file. 00309 \param s The T.4 context. 00310 \param model The model string, or NULL. */ 00311 SPAN_DECLARE(void) t4_rx_set_model(t4_state_t *s, const char *model); 00312 00313 /*! \brief Prepare for transmission of a document. 00314 \param s The T.4 context. 00315 \param file The name of the file to be sent. 00316 \param start_page The first page to send. -1 for no restriction. 00317 \param stop_page The last page to send. -1 for no restriction. 00318 \return A pointer to the context, or NULL if there was a problem. */ 00319 SPAN_DECLARE(t4_state_t *) t4_tx_init(t4_state_t *s, const char *file, int start_page, int stop_page); 00320 00321 /*! \brief Prepare to send the next page of the current document. 00322 \param s The T.4 context. 00323 \return zero for success, -1 for failure. */ 00324 SPAN_DECLARE(int) t4_tx_start_page(t4_state_t *s); 00325 00326 /*! \brief Prepare the current page for a resend. 00327 \param s The T.4 context. 00328 \return zero for success, -1 for failure. */ 00329 SPAN_DECLARE(int) t4_tx_restart_page(t4_state_t *s); 00330 00331 /*! \brief Check for the existance of the next page, and whether its format is like the 00332 current one. This information can be needed before it is determined that the current 00333 page is finished with. 00334 \param s The T.4 context. 00335 \return 0 for next page found with the same format as the current page. 00336 1 for next page found with different format from the current page. 00337 -1 for no page found, or file failure. */ 00338 SPAN_DECLARE(int) t4_tx_next_page_has_different_format(t4_state_t *s); 00339 00340 /*! \brief Complete the sending of a page. 00341 \param s The T.4 context. 00342 \return zero for success, -1 for failure. */ 00343 SPAN_DECLARE(int) t4_tx_end_page(t4_state_t *s); 00344 00345 /*! \brief Get the next bit of the current document page. The document will 00346 be padded for the current minimum scan line time. If the 00347 file does not contain an RTC (return to control) code at 00348 the end of the page, one will be added where appropriate. 00349 \param s The T.4 context. 00350 \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is 00351 set (i.e. the returned value is 2 or 3). */ 00352 SPAN_DECLARE(int) t4_tx_get_bit(t4_state_t *s); 00353 00354 /*! \brief Get the next byte of the current document page. The document will 00355 be padded for the current minimum scan line time. If the 00356 file does not contain an RTC (return to control) code at 00357 the end of the page, one will be added where appropriate. 00358 \param s The T.4 context. 00359 \return The next byte. For the last byte of data, bit 8 is 00360 set. In this case, one or more bits of the byte may be padded with 00361 zeros, to complete the byte. */ 00362 SPAN_DECLARE(int) t4_tx_get_byte(t4_state_t *s); 00363 00364 /*! \brief Get the next chunk of the current document page. The document will 00365 be padded for the current minimum scan line time. If the 00366 file does not contain an RTC (return to control) code at 00367 the end of the page, one will be added where appropriate. 00368 \param s The T.4 context. 00369 \param buf The buffer into which the chunk is to written. 00370 \param max_len The maximum length of the chunk. 00371 \return The actual length of the chunk. If this is less than max_len it 00372 indicates that the end of the document has been reached. */ 00373 SPAN_DECLARE(int) t4_tx_get_chunk(t4_state_t *s, uint8_t buf[], int max_len); 00374 00375 /*! \brief Return the next bit of the current document page, without actually 00376 moving forward in the buffer. The document will be padded for the 00377 current minimum scan line time. If the file does not contain an 00378 RTC (return to control) code at the end of the page, one will be 00379 added. 00380 \param s The T.4 context. 00381 \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is 00382 set (i.e. the returned value is 2 or 3). */ 00383 SPAN_DECLARE(int) t4_tx_check_bit(t4_state_t *s); 00384 00385 /*! \brief End the transmission of a document. Tidy up and close the file. 00386 This should be used to end T.4 transmission started with t4_tx_init. 00387 \param s The T.4 context. 00388 \return 0 for success, otherwise -1. */ 00389 SPAN_DECLARE(int) t4_tx_release(t4_state_t *s); 00390 00391 /*! \brief End the transmission of a document. Tidy up, close the file and 00392 free the context. This should be used to end T.4 transmission 00393 started with t4_tx_init. 00394 \param s The T.4 context. 00395 \return 0 for success, otherwise -1. */ 00396 SPAN_DECLARE(int) t4_tx_free(t4_state_t *s); 00397 00398 /*! \brief Set the encoding for the encoded data. 00399 \param s The T.4 context. 00400 \param encoding The encoding. */ 00401 SPAN_DECLARE(void) t4_tx_set_tx_encoding(t4_state_t *s, int encoding); 00402 00403 /*! \brief Set the minimum number of encoded bits per row. This allows the 00404 makes the encoding process to be set to comply with the minimum row 00405 time specified by a remote receiving machine. 00406 \param s The T.4 context. 00407 \param bits The minimum number of bits per row. */ 00408 SPAN_DECLARE(void) t4_tx_set_min_row_bits(t4_state_t *s, int bits); 00409 00410 /*! \brief Set the identity of the local machine, for inclusion in page headers. 00411 \param s The T.4 context. 00412 \param ident The identity string. */ 00413 SPAN_DECLARE(void) t4_tx_set_local_ident(t4_state_t *s, const char *ident); 00414 00415 /*! Set the info field, included in the header line included in each page of an encoded 00416 FAX. This is a string of up to 50 characters. Other information (date, local ident, etc.) 00417 are automatically included in the header. If the header info is set to NULL or a zero 00418 length string, no header lines will be added to the encoded FAX. 00419 \brief Set the header info. 00420 \param s The T.4 context. 00421 \param info A string, of up to 50 bytes, which will form the info field. */ 00422 SPAN_DECLARE(void) t4_tx_set_header_info(t4_state_t *s, const char *info); 00423 00424 /*! \brief Set the row read handler for a T.4 transmit context. 00425 \param s The T.4 transmit context. 00426 \param handler A pointer to the handler routine. 00427 \param user_data An opaque pointer passed to the handler routine. 00428 \return 0 for success, otherwise -1. */ 00429 SPAN_DECLARE(int) t4_tx_set_row_read_handler(t4_state_t *s, t4_row_read_handler_t handler, void *user_data); 00430 00431 /*! \brief Get the row-to-row (y) resolution of the current page. 00432 \param s The T.4 context. 00433 \return The resolution, in pixels per metre. */ 00434 SPAN_DECLARE(int) t4_tx_get_y_resolution(t4_state_t *s); 00435 00436 /*! \brief Get the column-to-column (x) resolution of the current page. 00437 \param s The T.4 context. 00438 \return The resolution, in pixels per metre. */ 00439 SPAN_DECLARE(int) t4_tx_get_x_resolution(t4_state_t *s); 00440 00441 /*! \brief Get the width of the current page, in pixel columns. 00442 \param s The T.4 context. 00443 \return The number of columns. */ 00444 SPAN_DECLARE(int) t4_tx_get_image_width(t4_state_t *s); 00445 00446 /*! \brief Get the number of pages in the file. 00447 \param s The T.4 context. 00448 \return The number of pages, or -1 if there is an error. */ 00449 SPAN_DECLARE(int) t4_tx_get_pages_in_file(t4_state_t *s); 00450 00451 /*! \brief Get the currnet page number in the file. 00452 \param s The T.4 context. 00453 \return The page number, or -1 if there is an error. */ 00454 SPAN_DECLARE(int) t4_tx_get_current_page_in_file(t4_state_t *s); 00455 00456 /*! Get the current image transfer statistics. 00457 \brief Get the current transfer statistics. 00458 \param s The T.4 context. 00459 \param t A pointer to a statistics structure. */ 00460 SPAN_DECLARE(void) t4_get_transfer_statistics(t4_state_t *s, t4_stats_t *t); 00461 00462 /*! Get the short text name of an encoding format. 00463 \brief Get the short text name of an encoding format. 00464 \param encoding The encoding type. 00465 \return A pointer to the string. */ 00466 SPAN_DECLARE(const char *) t4_encoding_to_str(int encoding); 00467 00468 #if defined(__cplusplus) 00469 } 00470 #endif 00471 00472 #endif 00473 /*- End of file ------------------------------------------------------------*/