1 2#if 0 /* in case someone actually tries to compile this */ 3 4/* example.c - an example of using libpng 5 * Last changed in libpng 1.4.2 [May 6, 2010] 6 * This file has been placed in the public domain by the authors. 7 * Maintained 1998-2010 Glenn Randers-Pehrson 8 * Maintained 1996, 1997 Andreas Dilger) 9 * Written 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) 10 */ 11 12/* This is an example of how to use libpng to read and write PNG files. 13 * The file libpng.txt is much more verbose then this. If you have not 14 * read it, do so first. This was designed to be a starting point of an 15 * implementation. This is not officially part of libpng, is hereby placed 16 * in the public domain, and therefore does not require a copyright notice. 17 * 18 * This file does not currently compile, because it is missing certain 19 * parts, like allocating memory to hold an image. You will have to 20 * supply these parts to get it to compile. For an example of a minimal 21 * working PNG reader/writer, see pngtest.c, included in this distribution; 22 * see also the programs in the contrib directory. 23 */ 24 25#include "png.h" 26 27 /* The png_jmpbuf() macro, used in error handling, became available in 28 * libpng version 1.0.6. If you want to be able to run your code with older 29 * versions of libpng, you must define the macro yourself (but only if it 30 * is not already defined by libpng!). 31 */ 32 33#ifndef png_jmpbuf 34# define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf) 35#endif 36 37/* Check to see if a file is a PNG file using png_sig_cmp(). png_sig_cmp() 38 * returns zero if the image is a PNG and nonzero if it isn't a PNG. 39 * 40 * The function check_if_png() shown here, but not used, returns nonzero (true) 41 * if the file can be opened and is a PNG, 0 (false) otherwise. 42 * 43 * If this call is successful, and you are going to keep the file open, 44 * you should call png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK); once 45 * you have created the png_ptr, so that libpng knows your application 46 * has read that many bytes from the start of the file. Make sure you 47 * don't call png_set_sig_bytes() with more than 8 bytes read or give it 48 * an incorrect number of bytes read, or you will either have read too 49 * many bytes (your fault), or you are telling libpng to read the wrong 50 * number of magic bytes (also your fault). 51 * 52 * Many applications already read the first 2 or 4 bytes from the start 53 * of the image to determine the file type, so it would be easiest just 54 * to pass the bytes to png_sig_cmp() or even skip that if you know 55 * you have a PNG file, and call png_set_sig_bytes(). 56 */ 57#define PNG_BYTES_TO_CHECK 4 58int check_if_png(char *file_name, FILE **fp) 59{ 60 char buf[PNG_BYTES_TO_CHECK]; 61 62 /* Open the prospective PNG file. */ 63 if ((*fp = fopen(file_name, "rb")) == NULL) 64 return 0; 65 66 /* Read in some of the signature bytes */ 67 if (fread(buf, 1, PNG_BYTES_TO_CHECK, *fp) != PNG_BYTES_TO_CHECK) 68 return 0; 69 70 /* Compare the first PNG_BYTES_TO_CHECK bytes of the signature. 71 Return nonzero (true) if they match */ 72 73 return(!png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK)); 74} 75 76/* Read a PNG file. You may want to return an error code if the read 77 * fails (depending upon the failure). There are two "prototypes" given 78 * here - one where we are given the filename, and we need to open the 79 * file, and the other where we are given an open file (possibly with 80 * some or all of the magic bytes read - see comments above). 81 */ 82#ifdef open_file /* prototype 1 */ 83void read_png(char *file_name) /* We need to open the file */ 84{ 85 png_structp png_ptr; 86 png_infop info_ptr; 87 unsigned int sig_read = 0; 88 png_uint_32 width, height; 89 int bit_depth, color_type, interlace_type; 90 FILE *fp; 91 92 if ((fp = fopen(file_name, "rb")) == NULL) 93 return (ERROR); 94 95#else no_open_file /* prototype 2 */ 96void read_png(FILE *fp, unsigned int sig_read) /* File is already open */ 97{ 98 png_structp png_ptr; 99 png_infop info_ptr; 100 png_uint_32 width, height; 101 int bit_depth, color_type, interlace_type; 102#endif no_open_file /* Only use one prototype! */ 103 104 /* Create and initialize the png_struct with the desired error handler 105 * functions. If you want to use the default stderr and longjump method, 106 * you can supply NULL for the last three parameters. We also supply the 107 * the compiler header file version, so that we know if the application 108 * was compiled with a compatible version of the library. REQUIRED 109 */ 110 png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 111 png_voidp user_error_ptr, user_error_fn, user_warning_fn); 112 113 if (png_ptr == NULL) 114 { 115 fclose(fp); 116 return (ERROR); 117 } 118 119 /* Allocate/initialize the memory for image information. REQUIRED. */ 120 info_ptr = png_create_info_struct(png_ptr); 121 if (info_ptr == NULL) 122 { 123 fclose(fp); 124 png_destroy_read_struct(&png_ptr, NULL, NULL); 125 return (ERROR); 126 } 127 128 /* Set error handling if you are using the setjmp/longjmp method (this is 129 * the normal method of doing things with libpng). REQUIRED unless you 130 * set up your own error handlers in the png_create_read_struct() earlier. 131 */ 132 133 if (setjmp(png_jmpbuf(png_ptr))) 134 { 135 /* Free all of the memory associated with the png_ptr and info_ptr */ 136 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 137 fclose(fp); 138 /* If we get here, we had a problem reading the file */ 139 return (ERROR); 140 } 141 142 /* One of the following I/O initialization methods is REQUIRED */ 143#ifdef streams /* PNG file I/O method 1 */ 144 /* Set up the input control if you are using standard C streams */ 145 png_init_io(png_ptr, fp); 146 147#else no_streams /* PNG file I/O method 2 */ 148 /* If you are using replacement read functions, instead of calling 149 * png_init_io() here you would call: 150 */ 151 png_set_read_fn(png_ptr, (void *)user_io_ptr, user_read_fn); 152 /* where user_io_ptr is a structure you want available to the callbacks */ 153#endif no_streams /* Use only one I/O method! */ 154 155 /* If we have already read some of the signature */ 156 png_set_sig_bytes(png_ptr, sig_read); 157 158#ifdef hilevel 159 /* 160 * If you have enough memory to read in the entire image at once, 161 * and you need to specify only transforms that can be controlled 162 * with one of the PNG_TRANSFORM_* bits (this presently excludes 163 * quantizing, filling, setting background, and doing gamma 164 * adjustment), then you can read the entire image (including 165 * pixels) into the info structure with this call: 166 */ 167 png_read_png(png_ptr, info_ptr, png_transforms, NULL); 168 169#else 170 /* OK, you're doing it the hard way, with the lower-level functions */ 171 172 /* The call to png_read_info() gives us all of the information from the 173 * PNG file before the first IDAT (image data chunk). REQUIRED 174 */ 175 png_read_info(png_ptr, info_ptr); 176 177 png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, 178 &interlace_type, NULL, NULL); 179 180 /* Set up the data transformations you want. Note that these are all 181 * optional. Only call them if you want/need them. Many of the 182 * transformations only work on specific types of images, and many 183 * are mutually exclusive. 184 */ 185 186 /* Tell libpng to strip 16 bit/color files down to 8 bits/color */ 187 png_set_strip_16(png_ptr); 188 189 /* Strip alpha bytes from the input data without combining with the 190 * background (not recommended). 191 */ 192 png_set_strip_alpha(png_ptr); 193 194 /* Extract multiple pixels with bit depths of 1, 2, and 4 from a single 195 * byte into separate bytes (useful for paletted and grayscale images). 196 */ 197 png_set_packing(png_ptr); 198 199 /* Change the order of packed pixels to least significant bit first 200 * (not useful if you are using png_set_packing). */ 201 png_set_packswap(png_ptr); 202 203 /* Expand paletted colors into true RGB triplets */ 204 if (color_type == PNG_COLOR_TYPE_PALETTE) 205 png_set_palette_to_rgb(png_ptr); 206 207 /* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */ 208 if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) 209 png_set_expand_gray_1_2_4_to_8(png_ptr); 210 211 /* Expand paletted or RGB images with transparency to full alpha channels 212 * so the data will be available as RGBA quartets. 213 */ 214 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) 215 png_set_tRNS_to_alpha(png_ptr); 216 217 /* Set the background color to draw transparent and alpha images over. 218 * It is possible to set the red, green, and blue components directly 219 * for paletted images instead of supplying a palette index. Note that 220 * even if the PNG file supplies a background, you are not required to 221 * use it - you should use the (solid) application background if it has one. 222 */ 223 224 png_color_16 my_background, *image_background; 225 226 if (png_get_bKGD(png_ptr, info_ptr, &image_background)) 227 png_set_background(png_ptr, image_background, 228 PNG_BACKGROUND_GAMMA_FILE, 1, 1.0); 229 else 230 png_set_background(png_ptr, &my_background, 231 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0); 232 233 /* Some suggestions as to how to get a screen gamma value 234 * 235 * Note that screen gamma is the display_exponent, which includes 236 * the CRT_exponent and any correction for viewing conditions 237 */ 238 if (/* We have a user-defined screen gamma value */) 239 { 240 screen_gamma = user-defined screen_gamma; 241 } 242 /* This is one way that applications share the same screen gamma value */ 243 else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL) 244 { 245 screen_gamma = atof(gamma_str); 246 } 247 /* If we don't have another value */ 248 else 249 { 250 screen_gamma = 2.2; /* A good guess for a PC monitor in a dimly 251 lit room */ 252 screen_gamma = 1.7 or 1.0; /* A good guess for Mac systems */ 253 } 254 255 /* Tell libpng to handle the gamma conversion for you. The final call 256 * is a good guess for PC generated images, but it should be configurable 257 * by the user at run time by the user. It is strongly suggested that 258 * your application support gamma correction. 259 */ 260 261 int intent; 262 263 if (png_get_sRGB(png_ptr, info_ptr, &intent)) 264 png_set_gamma(png_ptr, screen_gamma, 0.45455); 265 else 266 { 267 double image_gamma; 268 if (png_get_gAMA(png_ptr, info_ptr, &image_gamma)) 269 png_set_gamma(png_ptr, screen_gamma, image_gamma); 270 else 271 png_set_gamma(png_ptr, screen_gamma, 0.45455); 272 } 273 274#ifdef PNG_READ_QUANTIZE_SUPPORTED 275 /* Quantize RGB files down to 8 bit palette or reduce palettes 276 * to the number of colors available on your screen. 277 */ 278 if (color_type & PNG_COLOR_MASK_COLOR) 279 { 280 int num_palette; 281 png_colorp palette; 282 283 /* This reduces the image to the application supplied palette */ 284 if (/* We have our own palette */) 285 { 286 /* An array of colors to which the image should be quantized */ 287 png_color std_color_cube[MAX_SCREEN_COLORS]; 288 289 /* Prior to libpng-1.4.2, this was png_set_dither(). */ 290 png_set_quantize(png_ptr, std_color_cube, MAX_SCREEN_COLORS, 291 MAX_SCREEN_COLORS, NULL, 0); 292 } 293 /* This reduces the image to the palette supplied in the file */ 294 else if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette)) 295 { 296 png_uint_16p histogram = NULL; 297 298 png_get_hIST(png_ptr, info_ptr, &histogram); 299 300 png_set_quantize(png_ptr, palette, num_palette, 301 max_screen_colors, histogram, 0); 302 } 303 } 304#endif /* PNG_READ_QUANTIZE_SUPPORTED */ 305 306 /* Invert monochrome files to have 0 as white and 1 as black */ 307 png_set_invert_mono(png_ptr); 308 309 /* If you want to shift the pixel values from the range [0,255] or 310 * [0,65535] to the original [0,7] or [0,31], or whatever range the 311 * colors were originally in: 312 */ 313 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_sBIT)) 314 { 315 png_color_8p sig_bit_p; 316 317 png_get_sBIT(png_ptr, info_ptr, &sig_bit_p); 318 png_set_shift(png_ptr, sig_bit_p); 319 } 320 321 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */ 322 if (color_type & PNG_COLOR_MASK_COLOR) 323 png_set_bgr(png_ptr); 324 325 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */ 326 png_set_swap_alpha(png_ptr); 327 328 /* Swap bytes of 16 bit files to least significant byte first */ 329 png_set_swap(png_ptr); 330 331 /* Add filler (or alpha) byte (before/after each RGB triplet) */ 332 png_set_filler(png_ptr, 0xff, PNG_FILLER_AFTER); 333 334 /* Turn on interlace handling. REQUIRED if you are not using 335 * png_read_image(). To see how to handle interlacing passes, 336 * see the png_read_row() method below: 337 */ 338 number_passes = png_set_interlace_handling(png_ptr); 339 340 /* Optional call to gamma correct and add the background to the palette 341 * and update info structure. REQUIRED if you are expecting libpng to 342 * update the palette for you (ie you selected such a transform above). 343 */ 344 png_read_update_info(png_ptr, info_ptr); 345 346 /* Allocate the memory to hold the image using the fields of info_ptr. */ 347 348 /* The easiest way to read the image: */ 349 png_bytep row_pointers[height]; 350 351 /* Clear the pointer array */ 352 for (row = 0; row < height; row++) 353 row_pointers[row] = NULL; 354 355 for (row = 0; row < height; row++) 356 row_pointers[row] = png_malloc(png_ptr, png_get_rowbytes(png_ptr, 357 info_ptr)); 358 359 /* Now it's time to read the image. One of these methods is REQUIRED */ 360#ifdef entire /* Read the entire image in one go */ 361 png_read_image(png_ptr, row_pointers); 362 363#else no_entire /* Read the image one or more scanlines at a time */ 364 /* The other way to read images - deal with interlacing: */ 365 366 for (pass = 0; pass < number_passes; pass++) 367 { 368#ifdef single /* Read the image a single row at a time */ 369 for (y = 0; y < height; y++) 370 { 371 png_read_rows(png_ptr, &row_pointers[y], NULL, 1); 372 } 373 374#else no_single /* Read the image several rows at a time */ 375 for (y = 0; y < height; y += number_of_rows) 376 { 377#ifdef sparkle /* Read the image using the "sparkle" effect. */ 378 png_read_rows(png_ptr, &row_pointers[y], NULL, 379 number_of_rows); 380#else no_sparkle /* Read the image using the "rectangle" effect */ 381 png_read_rows(png_ptr, NULL, &row_pointers[y], 382 number_of_rows); 383#endif no_sparkle /* Use only one of these two methods */ 384 } 385 386 /* If you want to display the image after every pass, do so here */ 387#endif no_single /* Use only one of these two methods */ 388 } 389#endif no_entire /* Use only one of these two methods */ 390 391 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */ 392 png_read_end(png_ptr, info_ptr); 393#endif hilevel 394 395 /* At this point you have read the entire image */ 396 397 /* Clean up after the read, and free any memory allocated - REQUIRED */ 398 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 399 400 /* Close the file */ 401 fclose(fp); 402 403 /* That's it */ 404 return (OK); 405} 406 407/* Progressively read a file */ 408 409int 410initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr) 411{ 412 /* Create and initialize the png_struct with the desired error handler 413 * functions. If you want to use the default stderr and longjump method, 414 * you can supply NULL for the last three parameters. We also check that 415 * the library version is compatible in case we are using dynamically 416 * linked libraries. 417 */ 418 *png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 419 png_voidp user_error_ptr, user_error_fn, user_warning_fn); 420 421 if (*png_ptr == NULL) 422 { 423 *info_ptr = NULL; 424 return (ERROR); 425 } 426 427 *info_ptr = png_create_info_struct(png_ptr); 428 429 if (*info_ptr == NULL) 430 { 431 png_destroy_read_struct(png_ptr, info_ptr, NULL); 432 return (ERROR); 433 } 434 435 if (setjmp(png_jmpbuf((*png_ptr)))) 436 { 437 png_destroy_read_struct(png_ptr, info_ptr, NULL); 438 return (ERROR); 439 } 440 441 /* This one's new. You will need to provide all three 442 * function callbacks, even if you aren't using them all. 443 * If you aren't using all functions, you can specify NULL 444 * parameters. Even when all three functions are NULL, 445 * you need to call png_set_progressive_read_fn(). 446 * These functions shouldn't be dependent on global or 447 * static variables if you are decoding several images 448 * simultaneously. You should store stream specific data 449 * in a separate struct, given as the second parameter, 450 * and retrieve the pointer from inside the callbacks using 451 * the function png_get_progressive_ptr(png_ptr). 452 */ 453 png_set_progressive_read_fn(*png_ptr, (void *)stream_data, 454 info_callback, row_callback, end_callback); 455 456 return (OK); 457} 458 459int 460process_data(png_structp *png_ptr, png_infop *info_ptr, 461 png_bytep buffer, png_uint_32 length) 462{ 463 if (setjmp(png_jmpbuf((*png_ptr)))) 464 { 465 /* Free the png_ptr and info_ptr memory on error */ 466 png_destroy_read_struct(png_ptr, info_ptr, NULL); 467 return (ERROR); 468 } 469 470 /* This one's new also. Simply give it chunks of data as 471 * they arrive from the data stream (in order, of course). 472 * On segmented machines, don't give it any more than 64K. 473 * The library seems to run fine with sizes of 4K, although 474 * you can give it much less if necessary (I assume you can 475 * give it chunks of 1 byte, but I haven't tried with less 476 * than 256 bytes yet). When this function returns, you may 477 * want to display any rows that were generated in the row 478 * callback, if you aren't already displaying them there. 479 */ 480 png_process_data(*png_ptr, *info_ptr, buffer, length); 481 return (OK); 482} 483 484info_callback(png_structp png_ptr, png_infop info) 485{ 486 /* Do any setup here, including setting any of the transformations 487 * mentioned in the Reading PNG files section. For now, you _must_ 488 * call either png_start_read_image() or png_read_update_info() 489 * after all the transformations are set (even if you don't set 490 * any). You may start getting rows before png_process_data() 491 * returns, so this is your last chance to prepare for that. 492 */ 493} 494 495row_callback(png_structp png_ptr, png_bytep new_row, 496 png_uint_32 row_num, int pass) 497{ 498 /* 499 * This function is called for every row in the image. If the 500 * image is interlaced, and you turned on the interlace handler, 501 * this function will be called for every row in every pass. 502 * 503 * In this function you will receive a pointer to new row data from 504 * libpng called new_row that is to replace a corresponding row (of 505 * the same data format) in a buffer allocated by your application. 506 * 507 * The new row data pointer "new_row" may be NULL, indicating there is 508 * no new data to be replaced (in cases of interlace loading). 509 * 510 * If new_row is not NULL then you need to call 511 * png_progressive_combine_row() to replace the corresponding row as 512 * shown below: 513 */ 514 515 /* Get pointer to corresponding row in our 516 * PNG read buffer. 517 */ 518 png_bytep old_row = ((png_bytep *)our_data)[row_num]; 519 520 /* If both rows are allocated then copy the new row 521 * data to the corresponding row data. 522 */ 523 if ((old_row != NULL) && (new_row != NULL)) 524 png_progressive_combine_row(png_ptr, old_row, new_row); 525 526 /* 527 * The rows and passes are called in order, so you don't really 528 * need the row_num and pass, but I'm supplying them because it 529 * may make your life easier. 530 * 531 * For the non-NULL rows of interlaced images, you must call 532 * png_progressive_combine_row() passing in the new row and the 533 * old row, as demonstrated above. You can call this function for 534 * NULL rows (it will just return) and for non-interlaced images 535 * (it just does the png_memcpy for you) if it will make the code 536 * easier. Thus, you can just do this for all cases: 537 */ 538 539 png_progressive_combine_row(png_ptr, old_row, new_row); 540 541 /* where old_row is what was displayed for previous rows. Note 542 * that the first pass (pass == 0 really) will completely cover 543 * the old row, so the rows do not have to be initialized. After 544 * the first pass (and only for interlaced images), you will have 545 * to pass the current row as new_row, and the function will combine 546 * the old row and the new row. 547 */ 548} 549 550end_callback(png_structp png_ptr, png_infop info) 551{ 552 /* This function is called when the whole image has been read, 553 * including any chunks after the image (up to and including 554 * the IEND). You will usually have the same info chunk as you 555 * had in the header, although some data may have been added 556 * to the comments and time fields. 557 * 558 * Most people won't do much here, perhaps setting a flag that 559 * marks the image as finished. 560 */ 561} 562 563/* Write a png file */ 564void write_png(char *file_name /* , ... other image information ... */) 565{ 566 FILE *fp; 567 png_structp png_ptr; 568 png_infop info_ptr; 569 png_colorp palette; 570 571 /* Open the file */ 572 fp = fopen(file_name, "wb"); 573 if (fp == NULL) 574 return (ERROR); 575 576 /* Create and initialize the png_struct with the desired error handler 577 * functions. If you want to use the default stderr and longjump method, 578 * you can supply NULL for the last three parameters. We also check that 579 * the library version is compatible with the one used at compile time, 580 * in case we are using dynamically linked libraries. REQUIRED. 581 */ 582 png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, 583 png_voidp user_error_ptr, user_error_fn, user_warning_fn); 584 585 if (png_ptr == NULL) 586 { 587 fclose(fp); 588 return (ERROR); 589 } 590 591 /* Allocate/initialize the image information data. REQUIRED */ 592 info_ptr = png_create_info_struct(png_ptr); 593 if (info_ptr == NULL) 594 { 595 fclose(fp); 596 png_destroy_write_struct(&png_ptr, NULL); 597 return (ERROR); 598 } 599 600 /* Set error handling. REQUIRED if you aren't supplying your own 601 * error handling functions in the png_create_write_struct() call. 602 */ 603 if (setjmp(png_jmpbuf(png_ptr))) 604 { 605 /* If we get here, we had a problem writing the file */ 606 fclose(fp); 607 png_destroy_write_struct(&png_ptr, &info_ptr); 608 return (ERROR); 609 } 610 611 /* One of the following I/O initialization functions is REQUIRED */ 612 613#ifdef streams /* I/O initialization method 1 */ 614 /* Set up the output control if you are using standard C streams */ 615 png_init_io(png_ptr, fp); 616 617#else no_streams /* I/O initialization method 2 */ 618 /* If you are using replacement write functions, instead of calling 619 * png_init_io() here you would call 620 */ 621 png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn, 622 user_IO_flush_function); 623 /* where user_io_ptr is a structure you want available to the callbacks */ 624#endif no_streams /* Only use one initialization method */ 625 626#ifdef hilevel 627 /* This is the easy way. Use it if you already have all the 628 * image info living in the structure. You could "|" many 629 * PNG_TRANSFORM flags into the png_transforms integer here. 630 */ 631 png_write_png(png_ptr, info_ptr, png_transforms, NULL); 632 633#else 634 /* This is the hard way */ 635 636 /* Set the image information here. Width and height are up to 2^31, 637 * bit_depth is one of 1, 2, 4, 8, or 16, but valid values also depend on 638 * the color_type selected. color_type is one of PNG_COLOR_TYPE_GRAY, 639 * PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLOR_TYPE_PALETTE, PNG_COLOR_TYPE_RGB, 640 * or PNG_COLOR_TYPE_RGB_ALPHA. interlace is either PNG_INTERLACE_NONE or 641 * PNG_INTERLACE_ADAM7, and the compression_type and filter_type MUST 642 * currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE. REQUIRED 643 */ 644 png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, PNG_COLOR_TYPE_???, 645 PNG_INTERLACE_????, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE); 646 647 /* Set the palette if there is one. REQUIRED for indexed-color images */ 648 palette = (png_colorp)png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH 649 * png_sizeof(png_color)); 650 /* ... Set palette colors ... */ 651 png_set_PLTE(png_ptr, info_ptr, palette, PNG_MAX_PALETTE_LENGTH); 652 /* You must not free palette here, because png_set_PLTE only makes a link to 653 * the palette that you malloced. Wait until you are about to destroy 654 * the png structure. 655 */ 656 657 /* Optional significant bit (sBIT) chunk */ 658 png_color_8 sig_bit; 659 /* If we are dealing with a grayscale image then */ 660 sig_bit.gray = true_bit_depth; 661 /* Otherwise, if we are dealing with a color image then */ 662 sig_bit.red = true_red_bit_depth; 663 sig_bit.green = true_green_bit_depth; 664 sig_bit.blue = true_blue_bit_depth; 665 /* If the image has an alpha channel then */ 666 sig_bit.alpha = true_alpha_bit_depth; 667 png_set_sBIT(png_ptr, info_ptr, &sig_bit); 668 669 670 /* Optional gamma chunk is strongly suggested if you have any guess 671 * as to the correct gamma of the image. 672 */ 673 png_set_gAMA(png_ptr, info_ptr, gamma); 674 675 /* Optionally write comments into the image */ 676 text_ptr[0].key = "Title"; 677 text_ptr[0].text = "Mona Lisa"; 678 text_ptr[0].compression = PNG_TEXT_COMPRESSION_NONE; 679 text_ptr[1].key = "Author"; 680 text_ptr[1].text = "Leonardo DaVinci"; 681 text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE; 682 text_ptr[2].key = "Description"; 683 text_ptr[2].text = "<long text>"; 684 text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt; 685#ifdef PNG_iTXt_SUPPORTED 686 text_ptr[0].lang = NULL; 687 text_ptr[0].lang_key = NULL; 688 text_ptr[1].lang = NULL; 689 text_ptr[1].lang_key = NULL; 690 text_ptr[2].lang = NULL; 691 text_ptr[2].lang_key = NULL; 692#endif 693 png_set_text(png_ptr, info_ptr, text_ptr, 3); 694 695 /* Other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs */ 696 697 /* Note that if sRGB is present the gAMA and cHRM chunks must be ignored 698 * on read and, if your application chooses to write them, they must 699 * be written in accordance with the sRGB profile 700 */ 701 702 /* Write the file header information. REQUIRED */ 703 png_write_info(png_ptr, info_ptr); 704 705 /* If you want, you can write the info in two steps, in case you need to 706 * write your private chunk ahead of PLTE: 707 * 708 * png_write_info_before_PLTE(write_ptr, write_info_ptr); 709 * write_my_chunk(); 710 * png_write_info(png_ptr, info_ptr); 711 * 712 * However, given the level of known- and unknown-chunk support in 1.2.0 713 * and up, this should no longer be necessary. 714 */ 715 716 /* Once we write out the header, the compression type on the text 717 * chunks gets changed to PNG_TEXT_COMPRESSION_NONE_WR or 718 * PNG_TEXT_COMPRESSION_zTXt_WR, so it doesn't get written out again 719 * at the end. 720 */ 721 722 /* Set up the transformations you want. Note that these are 723 * all optional. Only call them if you want them. 724 */ 725 726 /* Invert monochrome pixels */ 727 png_set_invert_mono(png_ptr); 728 729 /* Shift the pixels up to a legal bit depth and fill in 730 * as appropriate to correctly scale the image. 731 */ 732 png_set_shift(png_ptr, &sig_bit); 733 734 /* Pack pixels into bytes */ 735 png_set_packing(png_ptr); 736 737 /* Swap location of alpha bytes from ARGB to RGBA */ 738 png_set_swap_alpha(png_ptr); 739 740 /* Get rid of filler (OR ALPHA) bytes, pack XRGB/RGBX/ARGB/RGBA into 741 * RGB (4 channels -> 3 channels). The second parameter is not used. 742 */ 743 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE); 744 745 /* Flip BGR pixels to RGB */ 746 png_set_bgr(png_ptr); 747 748 /* Swap bytes of 16-bit files to most significant byte first */ 749 png_set_swap(png_ptr); 750 751 /* Swap bits of 1, 2, 4 bit packed pixel formats */ 752 png_set_packswap(png_ptr); 753 754 /* Turn on interlace handling if you are not using png_write_image() */ 755 if (interlacing) 756 number_passes = png_set_interlace_handling(png_ptr); 757 else 758 number_passes = 1; 759 760 /* The easiest way to write the image (you may have a different memory 761 * layout, however, so choose what fits your needs best). You need to 762 * use the first method if you aren't handling interlacing yourself. 763 */ 764 png_uint_32 k, height, width; 765 png_byte image[height][width*bytes_per_pixel]; 766 png_bytep row_pointers[height]; 767 768 if (height > PNG_UINT_32_MAX/png_sizeof(png_bytep)) 769 png_error (png_ptr, "Image is too tall to process in memory"); 770 771 for (k = 0; k < height; k++) 772 row_pointers[k] = image + k*width*bytes_per_pixel; 773 774 /* One of the following output methods is REQUIRED */ 775 776#ifdef entire /* Write out the entire image data in one call */ 777 png_write_image(png_ptr, row_pointers); 778 779 /* The other way to write the image - deal with interlacing */ 780 781#else no_entire /* Write out the image data by one or more scanlines */ 782 783 /* The number of passes is either 1 for non-interlaced images, 784 * or 7 for interlaced images. 785 */ 786 for (pass = 0; pass < number_passes; pass++) 787 { 788 /* Write a few rows at a time. */ 789 png_write_rows(png_ptr, &row_pointers[first_row], number_of_rows); 790 791 /* If you are only writing one row at a time, this works */ 792 for (y = 0; y < height; y++) 793 png_write_rows(png_ptr, &row_pointers[y], 1); 794 } 795#endif no_entire /* Use only one output method */ 796 797 /* You can write optional chunks like tEXt, zTXt, and tIME at the end 798 * as well. Shouldn't be necessary in 1.2.0 and up as all the public 799 * chunks are supported and you can use png_set_unknown_chunks() to 800 * register unknown chunks into the info structure to be written out. 801 */ 802 803 /* It is REQUIRED to call this to finish writing the rest of the file */ 804 png_write_end(png_ptr, info_ptr); 805#endif hilevel 806 807 /* If you png_malloced a palette, free it here (don't free info_ptr->palette, 808 * as recommended in versions 1.0.5m and earlier of this example; if 809 * libpng mallocs info_ptr->palette, libpng will free it). If you 810 * allocated it with malloc() instead of png_malloc(), use free() instead 811 * of png_free(). 812 */ 813 png_free(png_ptr, palette); 814 palette = NULL; 815 816 /* Similarly, if you png_malloced any data that you passed in with 817 * png_set_something(), such as a hist or trans array, free it here, 818 * when you can be sure that libpng is through with it. 819 */ 820 png_free(png_ptr, trans); 821 trans = NULL; 822 /* Whenever you use png_free() it is a good idea to set the pointer to 823 * NULL in case your application inadvertently tries to png_free() it 824 * again. When png_free() sees a NULL it returns without action, thus 825 * avoiding the double-free security problem. 826 */ 827 828 /* Clean up after the write, and free any memory allocated */ 829 png_destroy_write_struct(&png_ptr, &info_ptr); 830 831 /* Close the file */ 832 fclose(fp); 833 834 /* That's it */ 835 return (OK); 836} 837 838#endif /* if 0 */ 839