| 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 1.2.1 December 7, 2001. |
| 6 | * This file has been placed in the public domain by the authors. |
| 7 | * Maintained 1998-2007 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 |
| 58 | int 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 */ |
| 83 | void 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 */ |
| 95 | void 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_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 | for (row = 0; row < height; row++) |
| 346 | { |
| 347 | row_pointers[row] = png_malloc(png_ptr, png_get_rowbytes(png_ptr, |
| 348 | info_ptr)); |
| 349 | } |
| 350 | |
| 351 | /* Now it's time to read the image. One of these methods is REQUIRED */ |
| 352 | #ifdef entire /* Read the entire image in one go */ |
| 353 | png_read_image(png_ptr, row_pointers); |
| 354 | |
| 355 | #else no_entire /* Read the image one or more scanlines at a time */ |
| 356 | /* The other way to read images - deal with interlacing: */ |
| 357 | |
| 358 | for (pass = 0; pass < number_passes; pass++) |
| 359 | { |
| 360 | #ifdef single /* Read the image a single row at a time */ |
| 361 | for (y = 0; y < height; y++) |
| 362 | { |
| 363 | png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL, 1); |
| 364 | } |
| 365 | |
| 366 | #else no_single /* Read the image several rows at a time */ |
| 367 | for (y = 0; y < height; y += number_of_rows) |
| 368 | { |
| 369 | #ifdef sparkle /* Read the image using the "sparkle" effect. */ |
| 370 | png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL, |
| 371 | number_of_rows); |
| 372 | #else no_sparkle /* Read the image using the "rectangle" effect */ |
| 373 | png_read_rows(png_ptr, png_bytepp_NULL, &row_pointers[y], |
| 374 | number_of_rows); |
| 375 | #endif no_sparkle /* use only one of these two methods */ |
| 376 | } |
| 377 | |
| 378 | /* if you want to display the image after every pass, do |
| 379 | so here */ |
| 380 | #endif no_single /* use only one of these two methods */ |
| 381 | } |
| 382 | #endif no_entire /* use only one of these two methods */ |
| 383 | |
| 384 | /* read rest of file, and get additional chunks in info_ptr - REQUIRED */ |
| 385 | png_read_end(png_ptr, info_ptr); |
| 386 | #endif hilevel |
| 387 | |
| 388 | /* At this point you have read the entire image */ |
| 389 | |
| 390 | /* clean up after the read, and free any memory allocated - REQUIRED */ |
| 391 | png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL); |
| 392 | |
| 393 | /* close the file */ |
| 394 | fclose(fp); |
| 395 | |
| 396 | /* that's it */ |
| 397 | return (OK); |
| 398 | } |
| 399 | |
| 400 | /* progressively read a file */ |
| 401 | |
| 402 | int |
| 403 | initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr) |
| 404 | { |
| 405 | /* Create and initialize the png_struct with the desired error handler |
| 406 | * functions. If you want to use the default stderr and longjump method, |
| 407 | * you can supply NULL for the last three parameters. We also check that |
| 408 | * the library version is compatible in case we are using dynamically |
| 409 | * linked libraries. |
| 410 | */ |
| 411 | *png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, |
| 412 | png_voidp user_error_ptr, user_error_fn, user_warning_fn); |
| 413 | |
| 414 | if (*png_ptr == NULL) |
| 415 | { |
| 416 | *info_ptr = NULL; |
| 417 | return (ERROR); |
| 418 | } |
| 419 | |
| 420 | *info_ptr = png_create_info_struct(png_ptr); |
| 421 | |
| 422 | if (*info_ptr == NULL) |
| 423 | { |
| 424 | png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL); |
| 425 | return (ERROR); |
| 426 | } |
| 427 | |
| 428 | if (setjmp(png_jmpbuf((*png_ptr)))) |
| 429 | { |
| 430 | png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL); |
| 431 | return (ERROR); |
| 432 | } |
| 433 | |
| 434 | /* This one's new. You will need to provide all three |
| 435 | * function callbacks, even if you aren't using them all. |
| 436 | * If you aren't using all functions, you can specify NULL |
| 437 | * parameters. Even when all three functions are NULL, |
| 438 | * you need to call png_set_progressive_read_fn(). |
| 439 | * These functions shouldn't be dependent on global or |
| 440 | * static variables if you are decoding several images |
| 441 | * simultaneously. You should store stream specific data |
| 442 | * in a separate struct, given as the second parameter, |
| 443 | * and retrieve the pointer from inside the callbacks using |
| 444 | * the function png_get_progressive_ptr(png_ptr). |
| 445 | */ |
| 446 | png_set_progressive_read_fn(*png_ptr, (void *)stream_data, |
| 447 | info_callback, row_callback, end_callback); |
| 448 | |
| 449 | return (OK); |
| 450 | } |
| 451 | |
| 452 | int |
| 453 | process_data(png_structp *png_ptr, png_infop *info_ptr, |
| 454 | png_bytep buffer, png_uint_32 length) |
| 455 | { |
| 456 | if (setjmp(png_jmpbuf((*png_ptr)))) |
| 457 | { |
| 458 | /* Free the png_ptr and info_ptr memory on error */ |
| 459 | png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL); |
| 460 | return (ERROR); |
| 461 | } |
| 462 | |
| 463 | /* This one's new also. Simply give it chunks of data as |
| 464 | * they arrive from the data stream (in order, of course). |
| 465 | * On Segmented machines, don't give it any more than 64K. |
| 466 | * The library seems to run fine with sizes of 4K, although |
| 467 | * you can give it much less if necessary (I assume you can |
| 468 | * give it chunks of 1 byte, but I haven't tried with less |
| 469 | * than 256 bytes yet). When this function returns, you may |
| 470 | * want to display any rows that were generated in the row |
| 471 | * callback, if you aren't already displaying them there. |
| 472 | */ |
| 473 | png_process_data(*png_ptr, *info_ptr, buffer, length); |
| 474 | return (OK); |
| 475 | } |
| 476 | |
| 477 | info_callback(png_structp png_ptr, png_infop info) |
| 478 | { |
| 479 | /* do any setup here, including setting any of the transformations |
| 480 | * mentioned in the Reading PNG files section. For now, you _must_ |
| 481 | * call either png_start_read_image() or png_read_update_info() |
| 482 | * after all the transformations are set (even if you don't set |
| 483 | * any). You may start getting rows before png_process_data() |
| 484 | * returns, so this is your last chance to prepare for that. |
| 485 | */ |
| 486 | } |
| 487 | |
| 488 | row_callback(png_structp png_ptr, png_bytep new_row, |
| 489 | png_uint_32 row_num, int pass) |
| 490 | { |
| 491 | /* |
| 492 | * This function is called for every row in the image. If the |
| 493 | * image is interlaced, and you turned on the interlace handler, |
| 494 | * this function will be called for every row in every pass. |
| 495 | * |
| 496 | * In this function you will receive a pointer to new row data from |
| 497 | * libpng called new_row that is to replace a corresponding row (of |
| 498 | * the same data format) in a buffer allocated by your application. |
| 499 | * |
| 500 | * The new row data pointer new_row may be NULL, indicating there is |
| 501 | * no new data to be replaced (in cases of interlace loading). |
| 502 | * |
| 503 | * If new_row is not NULL then you need to call |
| 504 | * png_progressive_combine_row() to replace the corresponding row as |
| 505 | * shown below: |
| 506 | */ |
| 507 | /* Check if row_num is in bounds. */ |
| 508 | if((row_num >= 0) && (row_num < height)) |
| 509 | { |
| 510 | /* Get pointer to corresponding row in our |
| 511 | * PNG read buffer. |
| 512 | */ |
| 513 | png_bytep old_row = ((png_bytep *)our_data)[row_num]; |
| 514 | |
| 515 | /* If both rows are allocated then copy the new row |
| 516 | * data to the corresponding row data. |
| 517 | */ |
| 518 | if((old_row != NULL) && (new_row != NULL)) |
| 519 | png_progressive_combine_row(png_ptr, old_row, new_row); |
| 520 | } |
| 521 | /* |
| 522 | * The rows and passes are called in order, so you don't really |
| 523 | * need the row_num and pass, but I'm supplying them because it |
| 524 | * may make your life easier. |
| 525 | * |
| 526 | * For the non-NULL rows of interlaced images, you must call |
| 527 | * png_progressive_combine_row() passing in the new row and the |
| 528 | * old row, as demonstrated above. You can call this function for |
| 529 | * NULL rows (it will just return) and for non-interlaced images |
| 530 | * (it just does the png_memcpy for you) if it will make the code |
| 531 | * easier. Thus, you can just do this for all cases: |
| 532 | */ |
| 533 | |
| 534 | png_progressive_combine_row(png_ptr, old_row, new_row); |
| 535 | |
| 536 | /* where old_row is what was displayed for previous rows. Note |
| 537 | * that the first pass (pass == 0 really) will completely cover |
| 538 | * the old row, so the rows do not have to be initialized. After |
| 539 | * the first pass (and only for interlaced images), you will have |
| 540 | * to pass the current row as new_row, and the function will combine |
| 541 | * the old row and the new row. |
| 542 | */ |
| 543 | } |
| 544 | |
| 545 | end_callback(png_structp png_ptr, png_infop info) |
| 546 | { |
| 547 | /* this function is called when the whole image has been read, |
| 548 | * including any chunks after the image (up to and including |
| 549 | * the IEND). You will usually have the same info chunk as you |
| 550 | * had in the header, although some data may have been added |
| 551 | * to the comments and time fields. |
| 552 | * |
| 553 | * Most people won't do much here, perhaps setting a flag that |
| 554 | * marks the image as finished. |
| 555 | */ |
| 556 | } |
| 557 | |
| 558 | /* write a png file */ |
| 559 | void write_png(char *file_name /* , ... other image information ... */) |
| 560 | { |
| 561 | FILE *fp; |
| 562 | png_structp png_ptr; |
| 563 | png_infop info_ptr; |
| 564 | png_colorp palette; |
| 565 | |
| 566 | /* open the file */ |
| 567 | fp = fopen(file_name, "wb"); |
| 568 | if (fp == NULL) |
| 569 | return (ERROR); |
| 570 | |
| 571 | /* Create and initialize the png_struct with the desired error handler |
| 572 | * functions. If you want to use the default stderr and longjump method, |
| 573 | * you can supply NULL for the last three parameters. We also check that |
| 574 | * the library version is compatible with the one used at compile time, |
| 575 | * in case we are using dynamically linked libraries. REQUIRED. |
| 576 | */ |
| 577 | png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, |
| 578 | png_voidp user_error_ptr, user_error_fn, user_warning_fn); |
| 579 | |
| 580 | if (png_ptr == NULL) |
| 581 | { |
| 582 | fclose(fp); |
| 583 | return (ERROR); |
| 584 | } |
| 585 | |
| 586 | /* Allocate/initialize the image information data. REQUIRED */ |
| 587 | info_ptr = png_create_info_struct(png_ptr); |
| 588 | if (info_ptr == NULL) |
| 589 | { |
| 590 | fclose(fp); |
| 591 | png_destroy_write_struct(&png_ptr, png_infopp_NULL); |
| 592 | return (ERROR); |
| 593 | } |
| 594 | |
| 595 | /* Set error handling. REQUIRED if you aren't supplying your own |
| 596 | * error handling functions in the png_create_write_struct() call. |
| 597 | */ |
| 598 | if (setjmp(png_jmpbuf(png_ptr))) |
| 599 | { |
| 600 | /* If we get here, we had a problem reading the file */ |
| 601 | fclose(fp); |
| 602 | png_destroy_write_struct(&png_ptr, &info_ptr); |
| 603 | return (ERROR); |
| 604 | } |
| 605 | |
| 606 | /* One of the following I/O initialization functions is REQUIRED */ |
| 607 | #ifdef streams /* I/O initialization method 1 */ |
| 608 | /* set up the output control if you are using standard C streams */ |
| 609 | png_init_io(png_ptr, fp); |
| 610 | #else no_streams /* I/O initialization method 2 */ |
| 611 | /* If you are using replacement read functions, instead of calling |
| 612 | * png_init_io() here you would call */ |
| 613 | png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn, |
| 614 | user_IO_flush_function); |
| 615 | /* where user_io_ptr is a structure you want available to the callbacks */ |
| 616 | #endif no_streams /* only use one initialization method */ |
| 617 | |
| 618 | #ifdef hilevel |
| 619 | /* This is the easy way. Use it if you already have all the |
| 620 | * image info living info in the structure. You could "|" many |
| 621 | * PNG_TRANSFORM flags into the png_transforms integer here. |
| 622 | */ |
| 623 | png_write_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL); |
| 624 | #else |
| 625 | /* This is the hard way */ |
| 626 | |
| 627 | /* Set the image information here. Width and height are up to 2^31, |
| 628 | * bit_depth is one of 1, 2, 4, 8, or 16, but valid values also depend on |
| 629 | * the color_type selected. color_type is one of PNG_COLOR_TYPE_GRAY, |
| 630 | * PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLOR_TYPE_PALETTE, PNG_COLOR_TYPE_RGB, |
| 631 | * or PNG_COLOR_TYPE_RGB_ALPHA. interlace is either PNG_INTERLACE_NONE or |
| 632 | * PNG_INTERLACE_ADAM7, and the compression_type and filter_type MUST |
| 633 | * currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE. REQUIRED |
| 634 | */ |
| 635 | png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, PNG_COLOR_TYPE_???, |
| 636 | PNG_INTERLACE_????, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE); |
| 637 | |
| 638 | /* set the palette if there is one. REQUIRED for indexed-color images */ |
| 639 | palette = (png_colorp)png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH |
| 640 | * png_sizeof (png_color)); |
| 641 | /* ... set palette colors ... */ |
| 642 | png_set_PLTE(png_ptr, info_ptr, palette, PNG_MAX_PALETTE_LENGTH); |
| 643 | /* You must not free palette here, because png_set_PLTE only makes a link to |
| 644 | the palette that you malloced. Wait until you are about to destroy |
| 645 | the png structure. */ |
| 646 | |
| 647 | /* optional significant bit chunk */ |
| 648 | /* if we are dealing with a grayscale image then */ |
| 649 | sig_bit.gray = true_bit_depth; |
| 650 | /* otherwise, if we are dealing with a color image then */ |
| 651 | sig_bit.red = true_red_bit_depth; |
| 652 | sig_bit.green = true_green_bit_depth; |
| 653 | sig_bit.blue = true_blue_bit_depth; |
| 654 | /* if the image has an alpha channel then */ |
| 655 | sig_bit.alpha = true_alpha_bit_depth; |
| 656 | png_set_sBIT(png_ptr, info_ptr, sig_bit); |
| 657 | |
| 658 | |
| 659 | /* Optional gamma chunk is strongly suggested if you have any guess |
| 660 | * as to the correct gamma of the image. |
| 661 | */ |
| 662 | png_set_gAMA(png_ptr, info_ptr, gamma); |
| 663 | |
| 664 | /* Optionally write comments into the image */ |
| 665 | text_ptr[0].key = "Title"; |
| 666 | text_ptr[0].text = "Mona Lisa"; |
| 667 | text_ptr[0].compression = PNG_TEXT_COMPRESSION_NONE; |
| 668 | text_ptr[1].key = "Author"; |
| 669 | text_ptr[1].text = "Leonardo DaVinci"; |
| 670 | text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE; |
| 671 | text_ptr[2].key = "Description"; |
| 672 | text_ptr[2].text = "<long text>"; |
| 673 | text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt; |
| 674 | #ifdef PNG_iTXt_SUPPORTED |
| 675 | text_ptr[0].lang = NULL; |
| 676 | text_ptr[1].lang = NULL; |
| 677 | text_ptr[2].lang = NULL; |
| 678 | #endif |
| 679 | png_set_text(png_ptr, info_ptr, text_ptr, 3); |
| 680 | |
| 681 | /* other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs, */ |
| 682 | /* note that if sRGB is present the gAMA and cHRM chunks must be ignored |
| 683 | * on read and must be written in accordance with the sRGB profile */ |
| 684 | |
| 685 | /* Write the file header information. REQUIRED */ |
| 686 | png_write_info(png_ptr, info_ptr); |
| 687 | |
| 688 | /* If you want, you can write the info in two steps, in case you need to |
| 689 | * write your private chunk ahead of PLTE: |
| 690 | * |
| 691 | * png_write_info_before_PLTE(write_ptr, write_info_ptr); |
| 692 | * write_my_chunk(); |
| 693 | * png_write_info(png_ptr, info_ptr); |
| 694 | * |
| 695 | * However, given the level of known- and unknown-chunk support in 1.1.0 |
| 696 | * and up, this should no longer be necessary. |
| 697 | */ |
| 698 | |
| 699 | /* Once we write out the header, the compression type on the text |
| 700 | * chunks gets changed to PNG_TEXT_COMPRESSION_NONE_WR or |
| 701 | * PNG_TEXT_COMPRESSION_zTXt_WR, so it doesn't get written out again |
| 702 | * at the end. |
| 703 | */ |
| 704 | |
| 705 | /* set up the transformations you want. Note that these are |
| 706 | * all optional. Only call them if you want them. |
| 707 | */ |
| 708 | |
| 709 | /* invert monochrome pixels */ |
| 710 | png_set_invert_mono(png_ptr); |
| 711 | |
| 712 | /* Shift the pixels up to a legal bit depth and fill in |
| 713 | * as appropriate to correctly scale the image. |
| 714 | */ |
| 715 | png_set_shift(png_ptr, &sig_bit); |
| 716 | |
| 717 | /* pack pixels into bytes */ |
| 718 | png_set_packing(png_ptr); |
| 719 | |
| 720 | /* swap location of alpha bytes from ARGB to RGBA */ |
| 721 | png_set_swap_alpha(png_ptr); |
| 722 | |
| 723 | /* Get rid of filler (OR ALPHA) bytes, pack XRGB/RGBX/ARGB/RGBA into |
| 724 | * RGB (4 channels -> 3 channels). The second parameter is not used. |
| 725 | */ |
| 726 | png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE); |
| 727 | |
| 728 | /* flip BGR pixels to RGB */ |
| 729 | png_set_bgr(png_ptr); |
| 730 | |
| 731 | /* swap bytes of 16-bit files to most significant byte first */ |
| 732 | png_set_swap(png_ptr); |
| 733 | |
| 734 | /* swap bits of 1, 2, 4 bit packed pixel formats */ |
| 735 | png_set_packswap(png_ptr); |
| 736 | |
| 737 | /* turn on interlace handling if you are not using png_write_image() */ |
| 738 | if (interlacing) |
| 739 | number_passes = png_set_interlace_handling(png_ptr); |
| 740 | else |
| 741 | number_passes = 1; |
| 742 | |
| 743 | /* The easiest way to write the image (you may have a different memory |
| 744 | * layout, however, so choose what fits your needs best). You need to |
| 745 | * use the first method if you aren't handling interlacing yourself. |
| 746 | */ |
| 747 | png_uint_32 k, height, width; |
| 748 | png_byte image[height][width*bytes_per_pixel]; |
| 749 | png_bytep row_pointers[height]; |
| 750 | |
| 751 | if (height > PNG_UINT_32_MAX/png_sizeof(png_bytep)) |
| 752 | png_error (png_ptr, "Image is too tall to process in memory"); |
| 753 | |
| 754 | for (k = 0; k < height; k++) |
| 755 | row_pointers[k] = image + k*width*bytes_per_pixel; |
| 756 | |
| 757 | /* One of the following output methods is REQUIRED */ |
| 758 | #ifdef entire /* write out the entire image data in one call */ |
| 759 | png_write_image(png_ptr, row_pointers); |
| 760 | |
| 761 | /* the other way to write the image - deal with interlacing */ |
| 762 | |
| 763 | #else no_entire /* write out the image data by one or more scanlines */ |
| 764 | /* The number of passes is either 1 for non-interlaced images, |
| 765 | * or 7 for interlaced images. |
| 766 | */ |
| 767 | for (pass = 0; pass < number_passes; pass++) |
| 768 | { |
| 769 | /* Write a few rows at a time. */ |
| 770 | png_write_rows(png_ptr, &row_pointers[first_row], number_of_rows); |
| 771 | |
| 772 | /* If you are only writing one row at a time, this works */ |
| 773 | for (y = 0; y < height; y++) |
| 774 | { |
| 775 | png_write_rows(png_ptr, &row_pointers[y], 1); |
| 776 | } |
| 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 */ |