example.c revision 4215dd1533c56e1a89ae6f1d6ea68677fac27fda
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 1.2.35 [February 14, 2009] 6 * This file has been placed in the public domain by the authors. 7 * Maintained 1998-2009 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#else no_open_file /* prototype 2 */ 95void read_png(FILE *fp, unsigned int sig_read) /* file is already open */ 96{ 97 png_structp png_ptr; 98 png_infop info_ptr; 99 png_uint_32 width, height; 100 int bit_depth, color_type, interlace_type; 101#endif no_open_file /* only use one prototype! */ 102 103 /* Create and initialize the png_struct with the desired error handler 104 * functions. If you want to use the default stderr and longjump method, 105 * you can supply NULL for the last three parameters. We also supply the 106 * the compiler header file version, so that we know if the application 107 * was compiled with a compatible version of the library. REQUIRED 108 */ 109 png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 110 png_voidp user_error_ptr, user_error_fn, user_warning_fn); 111 112 if (png_ptr == NULL) 113 { 114 fclose(fp); 115 return (ERROR); 116 } 117 118 /* Allocate/initialize the memory for image information. REQUIRED. */ 119 info_ptr = png_create_info_struct(png_ptr); 120 if (info_ptr == NULL) 121 { 122 fclose(fp); 123 png_destroy_read_struct(&png_ptr, png_infopp_NULL, png_infopp_NULL); 124 return (ERROR); 125 } 126 127 /* Set error handling if you are using the setjmp/longjmp method (this is 128 * the normal method of doing things with libpng). REQUIRED unless you 129 * set up your own error handlers in the png_create_read_struct() earlier. 130 */ 131 132 if (setjmp(png_jmpbuf(png_ptr))) 133 { 134 /* Free all of the memory associated with the png_ptr and info_ptr */ 135 png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL); 136 fclose(fp); 137 /* If we get here, we had a problem reading the file */ 138 return (ERROR); 139 } 140 141 /* One of the following I/O initialization methods is REQUIRED */ 142#ifdef streams /* PNG file I/O method 1 */ 143 /* Set up the input control if you are using standard C streams */ 144 png_init_io(png_ptr, fp); 145 146#else no_streams /* PNG file I/O method 2 */ 147 /* If you are using replacement read functions, instead of calling 148 * png_init_io() here you would call: 149 */ 150 png_set_read_fn(png_ptr, (void *)user_io_ptr, user_read_fn); 151 /* where user_io_ptr is a structure you want available to the callbacks */ 152#endif no_streams /* Use only one I/O method! */ 153 154 /* If we have already read some of the signature */ 155 png_set_sig_bytes(png_ptr, sig_read); 156 157#ifdef hilevel 158 /* 159 * If you have enough memory to read in the entire image at once, 160 * and you need to specify only transforms that can be controlled 161 * with one of the PNG_TRANSFORM_* bits (this presently excludes 162 * dithering, filling, setting background, and doing gamma 163 * adjustment), then you can read the entire image (including 164 * pixels) into the info structure with this call: 165 */ 166 png_read_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL); 167#else 168 /* OK, you're doing it the hard way, with the lower-level functions */ 169 170 /* The call to png_read_info() gives us all of the information from the 171 * PNG file before the first IDAT (image data chunk). REQUIRED 172 */ 173 png_read_info(png_ptr, info_ptr); 174 175 png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, 176 &interlace_type, int_p_NULL, int_p_NULL); 177 178/* Set up the data transformations you want. Note that these are all 179 * optional. Only call them if you want/need them. Many of the 180 * transformations only work on specific types of images, and many 181 * are mutually exclusive. 182 */ 183 184 /* tell libpng to strip 16 bit/color files down to 8 bits/color */ 185 png_set_strip_16(png_ptr); 186 187 /* Strip alpha bytes from the input data without combining with the 188 * background (not recommended). 189 */ 190 png_set_strip_alpha(png_ptr); 191 192 /* Extract multiple pixels with bit depths of 1, 2, and 4 from a single 193 * byte into separate bytes (useful for paletted and grayscale images). 194 */ 195 png_set_packing(png_ptr); 196 197 /* Change the order of packed pixels to least significant bit first 198 * (not useful if you are using png_set_packing). */ 199 png_set_packswap(png_ptr); 200 201 /* Expand paletted colors into true RGB triplets */ 202 if (color_type == PNG_COLOR_TYPE_PALETTE) 203 png_set_palette_to_rgb(png_ptr); 204 205 /* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */ 206 if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) 207 png_set_expand_gray_1_2_4_to_8(png_ptr); 208 209 /* Expand paletted or RGB images with transparency to full alpha channels 210 * so the data will be available as RGBA quartets. 211 */ 212 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) 213 png_set_tRNS_to_alpha(png_ptr); 214 215 /* Set the background color to draw transparent and alpha images over. 216 * It is possible to set the red, green, and blue components directly 217 * for paletted images instead of supplying a palette index. Note that 218 * even if the PNG file supplies a background, you are not required to 219 * use it - you should use the (solid) application background if it has one. 220 */ 221 222 png_color_16 my_background, *image_background; 223 224 if (png_get_bKGD(png_ptr, info_ptr, &image_background)) 225 png_set_background(png_ptr, image_background, 226 PNG_BACKGROUND_GAMMA_FILE, 1, 1.0); 227 else 228 png_set_background(png_ptr, &my_background, 229 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0); 230 231 /* Some suggestions as to how to get a screen gamma value */ 232 233 /* Note that screen gamma is the display_exponent, which includes 234 * the CRT_exponent and any correction for viewing conditions */ 235 if (/* We have a user-defined screen gamma value */) 236 { 237 screen_gamma = user-defined screen_gamma; 238 } 239 /* This is one way that applications share the same screen gamma value */ 240 else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL) 241 { 242 screen_gamma = atof(gamma_str); 243 } 244 /* If we don't have another value */ 245 else 246 { 247 screen_gamma = 2.2; /* A good guess for a PC monitors in a dimly 248 lit room */ 249 screen_gamma = 1.7 or 1.0; /* A good guess for Mac systems */ 250 } 251 252 /* Tell libpng to handle the gamma conversion for you. The final call 253 * is a good guess for PC generated images, but it should be configurable 254 * by the user at run time by the user. It is strongly suggested that 255 * your application support gamma correction. 256 */ 257 258 int intent; 259 260 if (png_get_sRGB(png_ptr, info_ptr, &intent)) 261 png_set_gamma(png_ptr, screen_gamma, 0.45455); 262 else 263 { 264 double image_gamma; 265 if (png_get_gAMA(png_ptr, info_ptr, &image_gamma)) 266 png_set_gamma(png_ptr, screen_gamma, image_gamma); 267 else 268 png_set_gamma(png_ptr, screen_gamma, 0.45455); 269 } 270 271 /* Dither RGB files down to 8 bit palette or reduce palettes 272 * to the number of colors available on your screen. 273 */ 274 if (color_type & PNG_COLOR_MASK_COLOR) 275 { 276 int num_palette; 277 png_colorp palette; 278 279 /* This reduces the image to the application supplied palette */ 280 if (/* we have our own palette */) 281 { 282 /* An array of colors to which the image should be dithered */ 283 png_color std_color_cube[MAX_SCREEN_COLORS]; 284 285 png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS, 286 MAX_SCREEN_COLORS, png_uint_16p_NULL, 0); 287 } 288 /* This reduces the image to the palette supplied in the file */ 289 else if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette)) 290 { 291 png_uint_16p histogram = NULL; 292 293 png_get_hIST(png_ptr, info_ptr, &histogram); 294 295 png_set_dither(png_ptr, palette, num_palette, 296 max_screen_colors, histogram, 0); 297 } 298 } 299 300 /* invert monochrome files to have 0 as white and 1 as black */ 301 png_set_invert_mono(png_ptr); 302 303 /* If you want to shift the pixel values from the range [0,255] or 304 * [0,65535] to the original [0,7] or [0,31], or whatever range the 305 * colors were originally in: 306 */ 307 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_sBIT)) 308 { 309 png_color_8p sig_bit; 310 311 png_get_sBIT(png_ptr, info_ptr, &sig_bit); 312 png_set_shift(png_ptr, sig_bit); 313 } 314 315 /* flip the RGB pixels to BGR (or RGBA to BGRA) */ 316 if (color_type & PNG_COLOR_MASK_COLOR) 317 png_set_bgr(png_ptr); 318 319 /* swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */ 320 png_set_swap_alpha(png_ptr); 321 322 /* swap bytes of 16 bit files to least significant byte first */ 323 png_set_swap(png_ptr); 324 325 /* Add filler (or alpha) byte (before/after each RGB triplet) */ 326 png_set_filler(png_ptr, 0xff, PNG_FILLER_AFTER); 327 328 /* Turn on interlace handling. REQUIRED if you are not using 329 * png_read_image(). To see how to handle interlacing passes, 330 * see the png_read_row() method below: 331 */ 332 number_passes = png_set_interlace_handling(png_ptr); 333 334 /* Optional call to gamma correct and add the background to the palette 335 * and update info structure. REQUIRED if you are expecting libpng to 336 * update the palette for you (ie you selected such a transform above). 337 */ 338 png_read_update_info(png_ptr, info_ptr); 339 340 /* Allocate the memory to hold the image using the fields of info_ptr. */ 341 342 /* The easiest way to read the image: */ 343 png_bytep row_pointers[height]; 344 345 /* Clear the pointer array */ 346 for (row = 0; row < height; row++) 347 row_pointers[row] = NULL; 348 349 for (row = 0; row < height; row++) 350 row_pointers[row] = png_malloc(png_ptr, png_get_rowbytes(png_ptr, 351 info_ptr)); 352 353 /* Now it's time to read the image. One of these methods is REQUIRED */ 354#ifdef entire /* Read the entire image in one go */ 355 png_read_image(png_ptr, row_pointers); 356 357#else no_entire /* Read the image one or more scanlines at a time */ 358 /* The other way to read images - deal with interlacing: */ 359 360 for (pass = 0; pass < number_passes; pass++) 361 { 362#ifdef single /* Read the image a single row at a time */ 363 for (y = 0; y < height; y++) 364 { 365 png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL, 1); 366 } 367 368#else no_single /* Read the image several rows at a time */ 369 for (y = 0; y < height; y += number_of_rows) 370 { 371#ifdef sparkle /* Read the image using the "sparkle" effect. */ 372 png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL, 373 number_of_rows); 374#else no_sparkle /* Read the image using the "rectangle" effect */ 375 png_read_rows(png_ptr, png_bytepp_NULL, &row_pointers[y], 376 number_of_rows); 377#endif no_sparkle /* use only one of these two methods */ 378 } 379 380 /* if you want to display the image after every pass, do 381 so here */ 382#endif no_single /* use only one of these two methods */ 383 } 384#endif no_entire /* use only one of these two methods */ 385 386 /* read rest of file, and get additional chunks in info_ptr - REQUIRED */ 387 png_read_end(png_ptr, info_ptr); 388#endif hilevel 389 390 /* At this point you have read the entire image */ 391 392 /* clean up after the read, and free any memory allocated - REQUIRED */ 393 png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL); 394 395 /* close the file */ 396 fclose(fp); 397 398 /* that's it */ 399 return (OK); 400} 401 402/* progressively read a file */ 403 404int 405initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr) 406{ 407 /* Create and initialize the png_struct with the desired error handler 408 * functions. If you want to use the default stderr and longjump method, 409 * you can supply NULL for the last three parameters. We also check that 410 * the library version is compatible in case we are using dynamically 411 * linked libraries. 412 */ 413 *png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 414 png_voidp user_error_ptr, user_error_fn, user_warning_fn); 415 416 if (*png_ptr == NULL) 417 { 418 *info_ptr = NULL; 419 return (ERROR); 420 } 421 422 *info_ptr = png_create_info_struct(png_ptr); 423 424 if (*info_ptr == NULL) 425 { 426 png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL); 427 return (ERROR); 428 } 429 430 if (setjmp(png_jmpbuf((*png_ptr)))) 431 { 432 png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL); 433 return (ERROR); 434 } 435 436 /* This one's new. You will need to provide all three 437 * function callbacks, even if you aren't using them all. 438 * If you aren't using all functions, you can specify NULL 439 * parameters. Even when all three functions are NULL, 440 * you need to call png_set_progressive_read_fn(). 441 * These functions shouldn't be dependent on global or 442 * static variables if you are decoding several images 443 * simultaneously. You should store stream specific data 444 * in a separate struct, given as the second parameter, 445 * and retrieve the pointer from inside the callbacks using 446 * the function png_get_progressive_ptr(png_ptr). 447 */ 448 png_set_progressive_read_fn(*png_ptr, (void *)stream_data, 449 info_callback, row_callback, end_callback); 450 451 return (OK); 452} 453 454int 455process_data(png_structp *png_ptr, png_infop *info_ptr, 456 png_bytep buffer, png_uint_32 length) 457{ 458 if (setjmp(png_jmpbuf((*png_ptr)))) 459 { 460 /* Free the png_ptr and info_ptr memory on error */ 461 png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL); 462 return (ERROR); 463 } 464 465 /* This one's new also. Simply give it chunks of data as 466 * they arrive from the data stream (in order, of course). 467 * On Segmented machines, don't give it any more than 64K. 468 * The library seems to run fine with sizes of 4K, although 469 * you can give it much less if necessary (I assume you can 470 * give it chunks of 1 byte, but I haven't tried with less 471 * than 256 bytes yet). When this function returns, you may 472 * want to display any rows that were generated in the row 473 * callback, if you aren't already displaying them there. 474 */ 475 png_process_data(*png_ptr, *info_ptr, buffer, length); 476 return (OK); 477} 478 479info_callback(png_structp png_ptr, png_infop info) 480{ 481/* do any setup here, including setting any of the transformations 482 * mentioned in the Reading PNG files section. For now, you _must_ 483 * call either png_start_read_image() or png_read_update_info() 484 * after all the transformations are set (even if you don't set 485 * any). You may start getting rows before png_process_data() 486 * returns, so this is your last chance to prepare for that. 487 */ 488} 489 490row_callback(png_structp png_ptr, png_bytep new_row, 491 png_uint_32 row_num, int pass) 492{ 493/* 494 * This function is called for every row in the image. If the 495 * image is interlaced, and you turned on the interlace handler, 496 * this function will be called for every row in every pass. 497 * 498 * In this function you will receive a pointer to new row data from 499 * libpng called new_row that is to replace a corresponding row (of 500 * the same data format) in a buffer allocated by your application. 501 * 502 * The new row data pointer new_row may be NULL, indicating there is 503 * no new data to be replaced (in cases of interlace loading). 504 * 505 * If new_row is not NULL then you need to call 506 * png_progressive_combine_row() to replace the corresponding row as 507 * shown below: 508 */ 509 /* Check if row_num is in bounds. */ 510 if ((row_num >= 0) && (row_num < height)) 511 { 512 /* Get pointer to corresponding row in our 513 * PNG read buffer. 514 */ 515 png_bytep old_row = ((png_bytep *)our_data)[row_num]; 516 517 /* If both rows are allocated then copy the new row 518 * data to the corresponding row data. 519 */ 520 if ((old_row != NULL) && (new_row != NULL)) 521 png_progressive_combine_row(png_ptr, old_row, new_row); 522 } 523/* 524 * The rows and passes are called in order, so you don't really 525 * need the row_num and pass, but I'm supplying them because it 526 * may make your life easier. 527 * 528 * For the non-NULL rows of interlaced images, you must call 529 * png_progressive_combine_row() passing in the new row and the 530 * old row, as demonstrated above. You can call this function for 531 * NULL rows (it will just return) and for non-interlaced images 532 * (it just does the png_memcpy for you) if it will make the code 533 * easier. Thus, you can just do this for all cases: 534 */ 535 536 png_progressive_combine_row(png_ptr, old_row, new_row); 537 538/* where old_row is what was displayed for previous rows. Note 539 * that the first pass (pass == 0 really) will completely cover 540 * the old row, so the rows do not have to be initialized. After 541 * the first pass (and only for interlaced images), you will have 542 * to pass the current row as new_row, and the function will combine 543 * the old row and the new row. 544 */ 545} 546 547end_callback(png_structp png_ptr, png_infop info) 548{ 549/* this function is called when the whole image has been read, 550 * including any chunks after the image (up to and including 551 * the IEND). You will usually have the same info chunk as you 552 * had in the header, although some data may have been added 553 * to the comments and time fields. 554 * 555 * Most people won't do much here, perhaps setting a flag that 556 * marks the image as finished. 557 */ 558} 559 560/* write a png file */ 561void write_png(char *file_name /* , ... other image information ... */) 562{ 563 FILE *fp; 564 png_structp png_ptr; 565 png_infop info_ptr; 566 png_colorp palette; 567 568 /* open the file */ 569 fp = fopen(file_name, "wb"); 570 if (fp == NULL) 571 return (ERROR); 572 573 /* Create and initialize the png_struct with the desired error handler 574 * functions. If you want to use the default stderr and longjump method, 575 * you can supply NULL for the last three parameters. We also check that 576 * the library version is compatible with the one used at compile time, 577 * in case we are using dynamically linked libraries. REQUIRED. 578 */ 579 png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, 580 png_voidp user_error_ptr, user_error_fn, user_warning_fn); 581 582 if (png_ptr == NULL) 583 { 584 fclose(fp); 585 return (ERROR); 586 } 587 588 /* Allocate/initialize the image information data. REQUIRED */ 589 info_ptr = png_create_info_struct(png_ptr); 590 if (info_ptr == NULL) 591 { 592 fclose(fp); 593 png_destroy_write_struct(&png_ptr, png_infopp_NULL); 594 return (ERROR); 595 } 596 597 /* Set error handling. REQUIRED if you aren't supplying your own 598 * error handling functions in the png_create_write_struct() call. 599 */ 600 if (setjmp(png_jmpbuf(png_ptr))) 601 { 602 /* If we get here, we had a problem reading the file */ 603 fclose(fp); 604 png_destroy_write_struct(&png_ptr, &info_ptr); 605 return (ERROR); 606 } 607 608 /* One of the following I/O initialization functions is REQUIRED */ 609#ifdef streams /* I/O initialization method 1 */ 610 /* set up the output control if you are using standard C streams */ 611 png_init_io(png_ptr, fp); 612#else no_streams /* I/O initialization method 2 */ 613 /* If you are using replacement write functions, instead of calling 614 * png_init_io() here you would call */ 615 png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn, 616 user_IO_flush_function); 617 /* where user_io_ptr is a structure you want available to the callbacks */ 618#endif no_streams /* only use one initialization method */ 619 620#ifdef hilevel 621 /* This is the easy way. Use it if you already have all the 622 * image info living info in the structure. You could "|" many 623 * PNG_TRANSFORM flags into the png_transforms integer here. 624 */ 625 png_write_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL); 626#else 627 /* This is the hard way */ 628 629 /* Set the image information here. Width and height are up to 2^31, 630 * bit_depth is one of 1, 2, 4, 8, or 16, but valid values also depend on 631 * the color_type selected. color_type is one of PNG_COLOR_TYPE_GRAY, 632 * PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLOR_TYPE_PALETTE, PNG_COLOR_TYPE_RGB, 633 * or PNG_COLOR_TYPE_RGB_ALPHA. interlace is either PNG_INTERLACE_NONE or 634 * PNG_INTERLACE_ADAM7, and the compression_type and filter_type MUST 635 * currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE. REQUIRED 636 */ 637 png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, PNG_COLOR_TYPE_???, 638 PNG_INTERLACE_????, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE); 639 640 /* set the palette if there is one. REQUIRED for indexed-color images */ 641 palette = (png_colorp)png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH 642 * png_sizeof(png_color)); 643 /* ... set palette colors ... */ 644 png_set_PLTE(png_ptr, info_ptr, palette, PNG_MAX_PALETTE_LENGTH); 645 /* You must not free palette here, because png_set_PLTE only makes a link to 646 the palette that you malloced. Wait until you are about to destroy 647 the png structure. */ 648 649 /* optional significant bit chunk */ 650 /* if we are dealing with a grayscale image then */ 651 sig_bit.gray = true_bit_depth; 652 /* otherwise, if we are dealing with a color image then */ 653 sig_bit.red = true_red_bit_depth; 654 sig_bit.green = true_green_bit_depth; 655 sig_bit.blue = true_blue_bit_depth; 656 /* if the image has an alpha channel then */ 657 sig_bit.alpha = true_alpha_bit_depth; 658 png_set_sBIT(png_ptr, info_ptr, sig_bit); 659 660 661 /* Optional gamma chunk is strongly suggested if you have any guess 662 * as to the correct gamma of the image. 663 */ 664 png_set_gAMA(png_ptr, info_ptr, gamma); 665 666 /* Optionally write comments into the image */ 667 text_ptr[0].key = "Title"; 668 text_ptr[0].text = "Mona Lisa"; 669 text_ptr[0].compression = PNG_TEXT_COMPRESSION_NONE; 670 text_ptr[1].key = "Author"; 671 text_ptr[1].text = "Leonardo DaVinci"; 672 text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE; 673 text_ptr[2].key = "Description"; 674 text_ptr[2].text = "<long text>"; 675 text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt; 676#ifdef PNG_iTXt_SUPPORTED 677 text_ptr[0].lang = NULL; 678 text_ptr[1].lang = NULL; 679 text_ptr[2].lang = NULL; 680#endif 681 png_set_text(png_ptr, info_ptr, text_ptr, 3); 682 683 /* other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs, */ 684 /* note that if sRGB is present the gAMA and cHRM chunks must be ignored 685 * on read and must be written in accordance with the sRGB profile */ 686 687 /* Write the file header information. REQUIRED */ 688 png_write_info(png_ptr, info_ptr); 689 690 /* If you want, you can write the info in two steps, in case you need to 691 * write your private chunk ahead of PLTE: 692 * 693 * png_write_info_before_PLTE(write_ptr, write_info_ptr); 694 * write_my_chunk(); 695 * png_write_info(png_ptr, info_ptr); 696 * 697 * However, given the level of known- and unknown-chunk support in 1.1.0 698 * and up, this should no longer be necessary. 699 */ 700 701 /* Once we write out the header, the compression type on the text 702 * chunks gets changed to PNG_TEXT_COMPRESSION_NONE_WR or 703 * PNG_TEXT_COMPRESSION_zTXt_WR, so it doesn't get written out again 704 * at the end. 705 */ 706 707 /* set up the transformations you want. Note that these are 708 * all optional. Only call them if you want them. 709 */ 710 711 /* invert monochrome pixels */ 712 png_set_invert_mono(png_ptr); 713 714 /* Shift the pixels up to a legal bit depth and fill in 715 * as appropriate to correctly scale the image. 716 */ 717 png_set_shift(png_ptr, &sig_bit); 718 719 /* pack pixels into bytes */ 720 png_set_packing(png_ptr); 721 722 /* swap location of alpha bytes from ARGB to RGBA */ 723 png_set_swap_alpha(png_ptr); 724 725 /* Get rid of filler (OR ALPHA) bytes, pack XRGB/RGBX/ARGB/RGBA into 726 * RGB (4 channels -> 3 channels). The second parameter is not used. 727 */ 728 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE); 729 730 /* flip BGR pixels to RGB */ 731 png_set_bgr(png_ptr); 732 733 /* swap bytes of 16-bit files to most significant byte first */ 734 png_set_swap(png_ptr); 735 736 /* swap bits of 1, 2, 4 bit packed pixel formats */ 737 png_set_packswap(png_ptr); 738 739 /* turn on interlace handling if you are not using png_write_image() */ 740 if (interlacing) 741 number_passes = png_set_interlace_handling(png_ptr); 742 else 743 number_passes = 1; 744 745 /* The easiest way to write the image (you may have a different memory 746 * layout, however, so choose what fits your needs best). You need to 747 * use the first method if you aren't handling interlacing yourself. 748 */ 749 png_uint_32 k, height, width; 750 png_byte image[height][width*bytes_per_pixel]; 751 png_bytep row_pointers[height]; 752 753 if (height > PNG_UINT_32_MAX/png_sizeof(png_bytep)) 754 png_error (png_ptr, "Image is too tall to process in memory"); 755 756 for (k = 0; k < height; k++) 757 row_pointers[k] = image + k*width*bytes_per_pixel; 758 759 /* One of the following output methods is REQUIRED */ 760#ifdef entire /* write out the entire image data in one call */ 761 png_write_image(png_ptr, row_pointers); 762 763 /* the other way to write the image - deal with interlacing */ 764 765#else no_entire /* write out the image data by one or more scanlines */ 766 /* The number of passes is either 1 for non-interlaced images, 767 * or 7 for interlaced images. 768 */ 769 for (pass = 0; pass < number_passes; pass++) 770 { 771 /* Write a few rows at a time. */ 772 png_write_rows(png_ptr, &row_pointers[first_row], number_of_rows); 773 774 /* If you are only writing one row at a time, this works */ 775 for (y = 0; y < height; y++) 776 png_write_rows(png_ptr, &row_pointers[y], 1); 777 } 778#endif no_entire /* use only one output method */ 779 780 /* You can write optional chunks like tEXt, zTXt, and tIME at the end 781 * as well. Shouldn't be necessary in 1.1.0 and up as all the public 782 * chunks are supported and you can use png_set_unknown_chunks() to 783 * register unknown chunks into the info structure to be written out. 784 */ 785 786 /* It is REQUIRED to call this to finish writing the rest of the file */ 787 png_write_end(png_ptr, info_ptr); 788#endif hilevel 789 790 /* If you png_malloced a palette, free it here (don't free info_ptr->palette, 791 as recommended in versions 1.0.5m and earlier of this example; if 792 libpng mallocs info_ptr->palette, libpng will free it). If you 793 allocated it with malloc() instead of png_malloc(), use free() instead 794 of png_free(). */ 795 png_free(png_ptr, palette); 796 palette = NULL; 797 798 /* Similarly, if you png_malloced any data that you passed in with 799 png_set_something(), such as a hist or trans array, free it here, 800 when you can be sure that libpng is through with it. */ 801 png_free(png_ptr, trans); 802 trans = NULL; 803 804 /* clean up after the write, and free any memory allocated */ 805 png_destroy_write_struct(&png_ptr, &info_ptr); 806 807 /* close the file */ 808 fclose(fp); 809 810 /* that's it */ 811 return (OK); 812} 813 814#endif /* if 0 */ 815