/* loadpng, Allegro wrapper routines for libpng * by Peter Wang (tjaden@users.sf.net). */ #include #include #include #include #include "loadpng.h" /* We need internals _color_load_depth and _fixup_loaded_bitmap. The * first can be replaced by the new get_color_depth() function which * is in Allegro 4.1 branch. But it's not worth it to break 4.0 * compatibility. */ double _png_screen_gamma = -1.0; int _png_compression_level = Z_BEST_COMPRESSION; /* get_gamma: * Get screen gamma value one of three ways. */ static double get_gamma(void) { if (_png_screen_gamma == -1.0) { /* Use the environment variable if available. * 2.2 is a good guess for PC monitors. * 1.1 is good for my laptop. */ AL_CONST char *gamma_str = getenv("SCREEN_GAMMA"); return (gamma_str) ? atof(gamma_str) : 2.2; } return _png_screen_gamma; } static void user_error_fn(png_structp png_ptr, png_const_charp message) { jmp_buf *jmpbuf = (jmp_buf *)png_get_error_ptr(png_ptr); (void)message; longjmp(*jmpbuf, 1); } /* read_data: * Custom read function to use Allegro packfile routines, * rather than C streams (so we can read from datafiles!) */ static void read_data(png_structp png_ptr, png_bytep data, png_uint_32 length) { PACKFILE *f = (PACKFILE *)png_get_io_ptr(png_ptr); if ((png_uint_32)pack_fread(data, length, f) != length) png_error(png_ptr, "read error (loadpng calling pack_fread)"); } /* check_if_png: * Check if input file is really PNG format. */ #define PNG_BYTES_TO_CHECK 4 static int check_if_png(PACKFILE *fp) { unsigned char buf[PNG_BYTES_TO_CHECK]; ASSERT(fp); if (pack_fread(buf, PNG_BYTES_TO_CHECK, fp) != PNG_BYTES_TO_CHECK) return 0; return (png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK) == 0); } /* really_load_png: * Worker routine, used by load_png and load_memory_png. */ static BITMAP *really_load_png(png_structp png_ptr, png_infop info_ptr, RGB *pal) { BITMAP *bmp; PALETTE tmppal; png_uint_32 width, height, rowbytes; int bit_depth, color_type, interlace_type; double image_gamma, screen_gamma; int intent; int bpp, dest_bpp; int tRNS_to_alpha = FALSE; int number_passes, pass; ASSERT(png_ptr && info_ptr); /* The call to png_read_info() gives us all of the information from the * PNG file before the first IDAT (image data chunk). */ png_read_info(png_ptr, info_ptr); png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, &interlace_type, NULL, NULL); /* Extract multiple pixels with bit depths of 1, 2, and 4 from a single * byte into separate bytes (useful for paletted and grayscale images). */ png_set_packing(png_ptr); /* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */ if ((color_type == PNG_COLOR_TYPE_GRAY) && (bit_depth < 8)) png_set_expand(png_ptr); /* Adds a full alpha channel if there is transparency information * in a tRNS chunk. */ if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) { png_set_tRNS_to_alpha(png_ptr); tRNS_to_alpha = TRUE; } /* Convert 16-bits per colour component to 8-bits per colour component. */ if (bit_depth == 16) png_set_strip_16(png_ptr); /* Convert grayscale to RGB triplets */ if ((color_type == PNG_COLOR_TYPE_GRAY) || (color_type == PNG_COLOR_TYPE_GRAY_ALPHA)) png_set_gray_to_rgb(png_ptr); /* Optionally, tell libpng to handle the gamma correction for us. */ if (_png_screen_gamma != 0.0) { screen_gamma = get_gamma(); if (png_get_sRGB(png_ptr, info_ptr, &intent)) png_set_gamma(png_ptr, screen_gamma, 0.45455); else { if (png_get_gAMA(png_ptr, info_ptr, &image_gamma)) png_set_gamma(png_ptr, screen_gamma, image_gamma); else png_set_gamma(png_ptr, screen_gamma, 0.45455); } } /* Turn on interlace handling. */ number_passes = png_set_interlace_handling(png_ptr); /* Call to gamma correct and add the background to the palette * and update info structure. */ png_read_update_info(png_ptr, info_ptr); /* Even if the user doesn't supply space for a palette, we want * one for the load process. */ if (!pal) pal = tmppal; /* Palettes. */ if (color_type & PNG_COLOR_MASK_PALETTE) { int num_palette, i; png_colorp palette; if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette)) { /* We don't actually dither, we just copy the palette. */ for (i = 0; ((i < num_palette) && (i < 256)); i++) { pal[i].r = palette[i].red >> 2; /* 256 -> 64 */ pal[i].g = palette[i].green >> 2; pal[i].b = palette[i].blue >> 2; } for (; i < 256; i++) pal[i].r = pal[i].g = pal[i].b = 0; } } else { generate_332_palette(pal); } rowbytes = png_get_rowbytes(png_ptr, info_ptr); /* Allocate the memory to hold the image using the fields of info_ptr. */ bpp = rowbytes * 8 / width; /* Allegro cannot handle less than 8 bpp. */ if (bpp < 8) bpp = 8; dest_bpp = _color_load_depth(bpp, (bpp == 32)); bmp = create_bitmap_ex(bpp, width, height); /* Maybe flip RGB to BGR. */ if ((bpp == 24) || (bpp == 32)) { int c = makecol_depth(bpp, 0, 0, 255); unsigned char *pc = (unsigned char *)&c; if (pc[0] == 255) png_set_bgr(png_ptr); #ifdef ALLEGRO_BIG_ENDIAN png_set_swap_alpha(png_ptr); #endif } /* Read the image, one line at a line (easier to debug!) */ for (pass = 0; pass < number_passes; pass++) { png_uint_32 y; for (y = 0; y < height; y++) png_read_row(png_ptr, bmp->line[y], NULL); } /* Let Allegro convert the image into the desired colour depth. */ if (dest_bpp != bpp) bmp = _fixup_loaded_bitmap(bmp, pal, dest_bpp); /* Read rest of file, and get additional chunks in info_ptr. */ png_read_end(png_ptr, info_ptr); return bmp; } /* load_png: * Load a PNG file from disk, doing colour coversion if required. */ BITMAP *load_png(AL_CONST char *filename, RGB *pal) { PACKFILE *fp; BITMAP *bmp; ASSERT(filename); fp = pack_fopen(filename, "r"); if (!fp) return NULL; bmp = load_png_pf(fp, pal); pack_fclose(fp); return bmp; } /* load_png_pf: * Load a PNG file from disk, doing colour coversion if required. */ BITMAP *load_png_pf(PACKFILE *fp, RGB *pal) { jmp_buf jmpbuf; BITMAP *bmp; png_structp png_ptr; png_infop info_ptr; ASSERT(fp); if (!check_if_png(fp)) { return NULL; } /* Create and initialize the png_struct with the desired error handler * functions. If you want to use the default stderr and longjump method, * you can supply NULL for the last three parameters. We also supply the * the compiler header file version, so that we know if the application * was compiled with a compatible version of the library. */ png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, (void *)NULL, NULL, NULL); if (!png_ptr) { return NULL; } /* Allocate/initialize the memory for image information. */ info_ptr = png_create_info_struct(png_ptr); if (!info_ptr) { png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL); return NULL; } /* Set error handling. */ if (setjmp(jmpbuf)) { /* Free all of the memory associated with the png_ptr and info_ptr */ png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL); /* If we get here, we had a problem reading the file */ return NULL; } png_set_error_fn(png_ptr, jmpbuf, user_error_fn, NULL); /* Use Allegro packfile routines. */ png_set_read_fn(png_ptr, fp, (png_rw_ptr)read_data); /* We have already read some of the signature. */ png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK); /* Really load the image now. */ bmp = really_load_png(png_ptr, info_ptr, pal); /* Clean up after the read, and free any memory allocated. */ png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL); return bmp; } /* read_data_memory: * Custom reader function to read a PNG file from a memory buffer. */ typedef struct { AL_CONST unsigned char *buffer; png_uint_32 bufsize; png_uint_32 current_pos; } MEMORY_READER_STATE; static void read_data_memory(png_structp png_ptr, png_bytep data, png_uint_32 length) { MEMORY_READER_STATE *f = (MEMORY_READER_STATE *)png_get_io_ptr(png_ptr); if (length > (f->bufsize - f->current_pos)) png_error(png_ptr, "read error in read_data_memory (loadpng)"); memcpy(data, f->buffer + f->current_pos, length); f->current_pos += length; } /* check_if_png_memory: * Check if input buffer is really PNG format. */ static int check_if_png_memory(AL_CONST void *buffer) { unsigned char *buf = (unsigned char *)buffer; return (png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK) == 0); } /* load_memory_png: * Load a PNG file from memory, doing colour coversion if required. */ BITMAP *load_memory_png(AL_CONST void *buffer, int bufsize, RGB *pal) { jmp_buf jmpbuf; MEMORY_READER_STATE memory_reader_state; BITMAP *bmp; png_structp png_ptr; png_infop info_ptr; if (!buffer || (bufsize <= 0)) return NULL; if (!check_if_png_memory(buffer)) return NULL; /* Create and initialize the png_struct with the desired error handler * functions. If you want to use the default stderr and longjump method, * you can supply NULL for the last three parameters. We also supply the * the compiler header file version, so that we know if the application * was compiled with a compatible version of the library. */ png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, (void *)NULL, NULL, NULL); if (!png_ptr) return NULL; /* Allocate/initialize the memory for image information. */ info_ptr = png_create_info_struct(png_ptr); if (!info_ptr) { png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL); return NULL; } /* Set error handling. */ if (setjmp(jmpbuf)) { /* Free all of the memory associated with the png_ptr and info_ptr */ png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL); /* If we get here, we had a problem reading the file */ return NULL; } png_set_error_fn(png_ptr, jmpbuf, user_error_fn, NULL); /* Set up the reader state. */ memory_reader_state.buffer = (unsigned char *)buffer; memory_reader_state.bufsize = bufsize; memory_reader_state.current_pos = PNG_BYTES_TO_CHECK; /* Tell libpng to use our custom reader. */ png_set_read_fn(png_ptr, &memory_reader_state, (png_rw_ptr)read_data_memory); /* We have already read some of the signature. */ png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK); /* Really load the image now. */ bmp = really_load_png(png_ptr, info_ptr, pal); /* Clean up after the read, and free any memory allocated. */ png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL); return bmp; }