mirror of
https://git.code.sf.net/p/libpng/code.git
synced 2025-07-10 18:04:09 +02:00
Imported from libpng-0.99e.tar
This commit is contained in:
Glenn Randers-Pehrson
446
libpng.3
446
libpng.3
@@ -1,25 +1,10 @@
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.TH PNG 5 "February 8, 1998"
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.TH LIBPNG 3 "February 28, 1998"
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.SH NAME
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libpng \- Portable Network Graphics (PNG) format
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libpng \- Portable Network Graphics (PNG) Reference Library
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.SH SYNOPSIS
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#include <png.h>
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void png_build_gamma_table (png_structp png_ptr);
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void png_build_grayscale_palette (int bit_depth, png_colorp
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palette);
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void png_calculate_crc (png_structp png_ptr, png_bytep ptr,
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png_size_t length);
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void png_check_chunk_name (png_structp png_ptr, png_bytep
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chunk_name);
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png_size_t png_check_keyword (png_structp png_ptr, png_charp
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key, png_charpp new_key);
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int png_check_sig (png_bytep sig, int num);
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void png_chunk_error (png_structp png_ptr, png_const_charp
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@@ -28,9 +13,6 @@ error);
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void png_chunk_warning (png_structp png_ptr, png_const_charp
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message);
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void png_combine_row (png_structp png_ptr, png_bytep row, int
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mask);
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void png_convert_from_struct_tm (png_timep ptime, struct tm FAR
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* ttime);
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@@ -39,24 +21,12 @@ void png_convert_from_time_t (png_timep ptime, time_t ttime);
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png_charp png_convert_to_rfc1123 (png_structp png_ptr,
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png_timep ptime);
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void png_correct_palette (png_structp png_ptr, png_colorp
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palette, int num_palette);
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int png_crc_error (png_structp png_ptr);
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int png_crc_finish (png_structp png_ptr, png_uint_32 skip);
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void png_crc_read (png_structp png_ptr, png_bytep buf,
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png_size_t length);
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png_infop png_create_info_struct (png_structp png_ptr);
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png_structp png_create_read_struct (png_const_charp
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user_png_ver, voidp error_ptr, png_error_ptr error_fn,
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png_error_ptr warn_fn);
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png_voidp png_create_struct (int type);
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png_structp png_create_write_struct (png_const_charp
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user_png_ver, voidp error_ptr, png_error_ptr error_fn,
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png_error_ptr warn_fn);
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@@ -72,93 +42,11 @@ info_ptr_ptr);
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void png_destroy_read_struct (png_structpp png_ptr_ptr,
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png_infopp info_ptr_ptr, png_infopp end_info_ptr_ptr);
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void png_destroy_struct (png_voidp struct_ptr);
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void png_destroy_write_struct (png_structpp png_ptr_ptr,
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png_infopp info_ptr_ptr);
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void png_do_background (png_row_infop row_info, png_bytep row,
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png_color_16p trans_values, png_color_16p background,
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png_color_16p background_1, png_bytep gamma_table, png_bytep
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gamma_from_1, png_bytep gamma_to_1, png_uint_16pp gamma_16,
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png_uint_16pp gamma_16_from_1, png_uint_16pp gamma_16_to_1, int
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gamma_shift);
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void png_do_bgr (png_row_infop row_info, png_bytep row);
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void png_do_chop (png_row_infop row_info, png_bytep row);
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void png_do_dither (png_row_infop row_info, png_bytep row,
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png_bytep palette_lookup, png_bytep dither_lookup);
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void png_do_expand (png_row_infop row_info, png_bytep row,
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png_color_16p trans_value);
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void png_do_expand_palette (png_row_infop row_info, png_bytep
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row, png_colorp palette, png_bytep trans, int num_trans);
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void png_do_gamma (png_row_infop row_info, png_bytep row,
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png_bytep gamma_table, png_uint_16pp gamma_16_table, int
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gamma_shift);
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void png_do_gray_to_rgb (png_row_infop row_info, png_bytep
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row);
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void png_do_invert (png_row_infop row_info, png_bytep row);
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void png_do_pack (png_row_infop row_info, png_bytep row,
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png_uint_32 bit_depth);
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void png_do_packswap (png_row_infop row_info, png_bytep row);
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void png_do_read_filler (png_row_infop row_info, png_bytep row,
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png_uint_32 filler, png_uint_32 flags);
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void png_do_read_interlace (png_row_infop row_info, png_bytep
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row, int pass, png_uint_32 transformations);
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void png_do_read_invert_alpha (png_row_infop row_info,
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png_bytep row);
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void png_do_read_swap_alpha (png_row_infop row_info, png_bytep
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row);
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void png_do_read_transformations (png_structp png_ptr);
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void png_do_rgb_to_gray (png_row_infop row_info, png_bytep
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row);
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void png_do_shift (png_row_infop row_info, png_bytep row,
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png_color_8p bit_depth);
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void png_do_strip_filler (png_row_infop row_info, png_bytep
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row, png_uint_32 flags);
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void png_do_swap (png_row_infop row_info, png_bytep row);
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void png_do_unpack (png_row_infop row_info, png_bytep row);
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void png_do_unshift (png_row_infop row_info, png_bytep row,
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png_color_8p sig_bits);
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void png_do_write_interlace (png_row_infop row_info, png_bytep
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row, int pass);
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void png_do_write_invert_alpha (png_row_infop row_info,
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png_bytep row);
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void png_do_write_swap_alpha (png_row_infop row_info, png_bytep
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row);
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void png_do_write_transformations (png_structp png_ptr);
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void png_error (png_structp png_ptr, png_const_charp error);
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void *png_far_to_near (png_structp png_ptr,png_voidp ptr,
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int check);
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void png_flush (png_structp png_ptr);
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void png_free (png_structp png_ptr, png_voidp ptr);
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png_byte png_get_bit_depth (png_structp png_ptr, png_infop
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@@ -198,8 +86,6 @@ png_infop info_ptr);
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png_uint_32 png_get_image_width (png_structp png_ptr, png_infop
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info_ptr);
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png_int_32 png_get_int_32 (png_bytep buf);
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png_byte png_get_interlace_type (png_structp png_ptr, png_infop
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info_ptr);
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@@ -255,10 +141,6 @@ png_uint_32 png_get_tRNS (png_structp png_ptr, png_infop
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info_ptr, png_bytep *trans, int *num_trans, png_color_16p
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*trans_values);
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png_uint_16 png_get_uint_16 (png_bytep buf);
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png_uint_32 png_get_uint_32 (png_bytep buf);
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png_uint_32 png_get_valid (png_structp png_ptr, png_infop
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info_ptr, png_uint_32 flag);
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@@ -268,72 +150,22 @@ png_infop info_ptr);
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png_uint_32 png_get_x_offset_pixels (png_structp png_ptr,
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png_infop info_ptr);
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png_uint_32 png_get_x_pixels_per_meter (png_structp png_ptr,
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png_infop info_ptr);
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png_uint_32 png_get_y_offset_microns (png_structp png_ptr,
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png_infop info_ptr);
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png_uint_32 png_get_y_offset_pixels (png_structp png_ptr,
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png_infop info_ptr);
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void png_handle_bKGD (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_cHRM (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_gAMA (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_hIST (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_IEND (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_IHDR (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_oFFs (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_pCAL (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_pHYs (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_PLTE (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_sBIT (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_sRGB (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_tEXt (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_tIME (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_tRNS (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_handle_unknown (png_structp png_ptr, png_infop
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info_ptr, png_uint_32 length);
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void png_handle_zTXt (png_structp png_ptr, png_infop info_ptr,
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png_uint_32 length);
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void png_info_destroy (png_structp png_ptr, png_infop
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info_ptr);
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png_uint_32 png_get_y_pixels_per_meter (png_structp png_ptr,
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png_infop info_ptr);
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void png_info_init (png_infop info_ptr);
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void png_init_io (png_structp png_ptr, FILE *fp);
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void png_init_read_transformations (png_structp png_ptr);
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png_voidp png_malloc (png_structp png_ptr, png_uint_32 size);
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voidp png_memcpy (png_voidp s1, png_voidp s2, png_size_t size);
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@@ -349,109 +181,27 @@ s1, int value, png_uint_32 size);
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void png_process_data (png_structp png_ptr, png_infop info_ptr,
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png_bytep buffer, png_size_t buffer_size);
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void png_process_IDAT_data (png_structp png_ptr, png_bytep
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buffer, png_size_t buffer_length);
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void png_process_some_data (png_structp png_ptr, png_infop
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info_ptr);
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void png_progressive_combine_row (png_structp png_ptr,
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png_bytep old_row, png_bytep new_row);
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void png_push_check_crc (png_structp png_ptr);
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void png_push_crc_finish (png_structp png_ptr);
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void png_push_crc_skip (png_structp png_ptr, png_uint_32
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length);
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void png_push_fill_buffer (png_structp png_ptr, png_bytep
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buffer, png_size_t length);
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void png_push_handle_tEXt (png_structp png_ptr, png_infop
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info_ptr, png_uint_32 length);
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void png_push_handle_unknown (png_structp png_ptr, png_infop
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info_ptr, png_uint_32 length);
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void png_push_handle_zTXt (png_structp png_ptr, png_infop
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info_ptr, png_uint_32 length);
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void png_push_have_end (png_structp png_ptr, png_infop
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info_ptr);
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void png_push_have_info (png_structp png_ptr, png_infop
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info_ptr);
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void png_push_have_row (png_structp png_ptr, png_bytep row);
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void png_push_process_row (png_structp png_ptr);
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void png_push_read_chunk (png_structp png_ptr, png_infop
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info_ptr);
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void png_push_read_end (png_structp png_ptr, png_infop
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info_ptr);
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void png_push_read_IDAT (png_structp png_ptr);
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void png_push_read_sig (png_structp png_ptr, png_infop
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info_ptr);
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void png_push_read_tEXt (png_structp png_ptr, png_infop
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info_ptr);
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void png_push_read_zTXt (png_structp png_ptr, png_infop
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info_ptr);
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void png_push_restore_buffer (png_structp png_ptr, png_bytep
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buffer, png_size_t buffer_length);
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void png_push_save_buffer (png_structp png_ptr);
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void png_read_data (png_structp png_ptr, png_bytep data,
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png_size_t length);
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void png_read_destroy (png_structp png_ptr, png_infop info_ptr,
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png_infop end_info_ptr);
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void png_read_end (png_structp png_ptr, png_infop info_ptr);
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void png_read_filter_row (png_structp png_ptr, png_row_infop
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row_info, png_bytep row, png_bytep prev_row, int filter);
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void png_read_finish_row (png_structp png_ptr);
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void png_read_image (png_structp png_ptr, png_bytepp image);
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void png_read_info (png_structp png_ptr, png_infop info_ptr);
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void png_read_init (png_structp png_ptr);
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void png_read_push_finish_row (png_structp png_ptr);
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void png_read_row (png_structp png_ptr, png_bytep row,
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png_bytep display_row);
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|
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void png_read_rows (png_structp png_ptr, png_bytepp row,
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png_bytepp display_row, png_uint_32 num_rows);
|
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|
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void png_read_start_row (png_structp png_ptr);
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|
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void png_read_transform_info (png_structp png_ptr, png_infop
|
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info_ptr);
|
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|
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void png_read_update_info (png_structp png_ptr, png_infop
|
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info_ptr);
|
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|
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void png_reset_crc (png_structp png_ptr);
|
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|
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void png_save_int_32 (png_bytep buf, png_int_32 i);
|
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|
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void png_save_uint_16 (png_bytep buf, unsigned int i);
|
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|
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void png_save_uint_32 (png_bytep buf, png_uint_32 i);
|
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|
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void png_set_background (png_structp png_ptr, png_color_16p
|
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background_color, int background_gamma_code, int need_expand,
|
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double background_gamma);
|
||||
@@ -595,9 +345,6 @@ void png_start_read_image (png_structp png_ptr);
|
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void png_warning (png_structp png_ptr, png_const_charp
|
||||
message);
|
||||
|
||||
void png_write_bKGD (png_structp png_ptr, png_color_16p values,
|
||||
int color_type);
|
||||
|
||||
void png_write_chunk (png_structp png_ptr, png_bytep
|
||||
chunk_name, png_bytep data, png_size_t length);
|
||||
|
||||
@@ -609,92 +356,23 @@ void png_write_chunk_end (png_structp png_ptr);
|
||||
void png_write_chunk_start (png_structp png_ptr, png_bytep
|
||||
chunk_name, png_uint_32 length);
|
||||
|
||||
void png_write_cHRM (png_structp png_ptr, double white_x,
|
||||
double white_y, double red_x, double red_y, double green_x,
|
||||
double green_y, double blue_x, double blue_y);
|
||||
|
||||
void png_write_data (png_structp png_ptr, png_bytep data,
|
||||
png_size_t length);
|
||||
|
||||
void png_write_destroy (png_structp png_ptr);
|
||||
|
||||
void png_write_destroy_info (png_infop info_ptr);
|
||||
|
||||
void png_write_end (png_structp png_ptr, png_infop info_ptr);
|
||||
|
||||
void png_write_filtered_row (png_structp png_ptr, png_bytep
|
||||
filtered_row);
|
||||
|
||||
void png_write_find_filter (png_structp png_ptr, png_row_infop
|
||||
row_info);
|
||||
|
||||
void png_write_finish_row (png_structp png_ptr);
|
||||
|
||||
void png_write_flush (png_structp png_ptr);
|
||||
|
||||
void png_write_gAMA (png_structp png_ptr, double file_gamma);
|
||||
|
||||
void png_write_hIST (png_structp png_ptr, png_uint_16p hist,
|
||||
int num_hist);
|
||||
|
||||
|
||||
void png_write_image (png_structp png_ptr, png_bytepp image);
|
||||
|
||||
void png_write_info (png_structp png_ptr, png_infop info_ptr);
|
||||
|
||||
void png_write_init (png_structp png_ptr);
|
||||
|
||||
void png_write_IDAT (png_structp png_ptr, png_bytep data,
|
||||
png_size_t length);
|
||||
|
||||
void png_write_IEND (png_structp png_ptr);
|
||||
|
||||
void png_write_IHDR (png_structp png_ptr, png_uint_32 width,
|
||||
png_uint_32 height, int bit_depth, int color_type, int
|
||||
compression_type, int filter_type, int interlace_type);
|
||||
|
||||
void png_write_oFFs (png_structp png_ptr, png_uint_32 x_offset,
|
||||
png_uint_32 y_offset, int unit_type);
|
||||
|
||||
void png_write_pCAL (png_structp png_ptr, png_charp purpose,
|
||||
png_int_32 X0, png_int_32 X1, int type, int nparams, png_charp
|
||||
units, png_charpp params);
|
||||
|
||||
void png_write_pHYs (png_structp png_ptr, png_uint_32
|
||||
x_pixels_per_unit, png_uint_32 y_pixels_per_unit, int
|
||||
unit_type);
|
||||
|
||||
void png_write_PLTE (png_structp png_ptr, png_colorp palette,
|
||||
png_uint_32 num_pal);
|
||||
|
||||
void png_write_row (png_structp png_ptr, png_bytep row);
|
||||
|
||||
void png_write_rows (png_structp png_ptr, png_bytepp row,
|
||||
png_uint_32 num_rows);
|
||||
|
||||
void png_write_sBIT (png_structp png_ptr, png_color_8p sbit,
|
||||
int color_type);
|
||||
|
||||
void png_write_sig (png_structp png_ptr);
|
||||
|
||||
void png_write_sRGB (png_structp png_ptr, int intent);
|
||||
|
||||
void png_write_start_row (png_structp png_ptr);
|
||||
|
||||
void png_write_tEXt (png_structp png_ptr, png_charp key,
|
||||
png_charp text, png_size_t text_len);
|
||||
|
||||
void png_write_tIME (png_structp png_ptr, png_timep mod_time);
|
||||
|
||||
void png_write_tRNS (png_structp png_ptr, png_bytep trans,
|
||||
png_color_16p values, int number, int color_type);
|
||||
|
||||
void png_write_zTXt (png_structp png_ptr, png_charp key,
|
||||
png_charp text, png_size_t text_len, int compression);
|
||||
|
||||
voidpf png_zalloc (voidpf png_ptr, uInt items, uInt size);
|
||||
|
||||
void png_zfree (voidpf png_ptr, voidpf ptr);
|
||||
|
||||
.SH DESCRIPTION
|
||||
The
|
||||
.I libpng
|
||||
@@ -706,11 +384,11 @@ Following is a copy of the libpng.txt file that accompanies libpng.
|
||||
.SH LIBPNG.TXT
|
||||
libpng.txt - A description on how to use and modify libpng
|
||||
|
||||
libpng version 0.99d
|
||||
libpng version 0.99e
|
||||
Updated and distributed by Glenn Randers-Pehrson
|
||||
<randeg@alumni.rpi.edu>
|
||||
Copyright (c) 1998, Glenn Randers-Pehrson
|
||||
February 8, 1998
|
||||
February 28, 1998
|
||||
|
||||
based on:
|
||||
|
||||
@@ -780,9 +458,7 @@ same instance of a structure.
|
||||
There are two main structures that are important to libpng, png_struct
|
||||
and png_info. The first, png_struct, is an internal structure that
|
||||
will not, for the most part, be used by a user except as the first
|
||||
variable passed to every libpng function call. It is not actually
|
||||
used in many of the functions; do not be alarmed about compiler
|
||||
warnings that say something to the effect that "png_ptr is not used."
|
||||
variable passed to every libpng function call.
|
||||
|
||||
The png_info structure is designed to provide information about the
|
||||
PNG file. At one time, the fields of png_info were intended to be
|
||||
@@ -964,8 +640,8 @@ Functions are used to get the information from the info_ptr:
|
||||
for PNG 1.0)
|
||||
compression_type - (must be PNG_COMPRESSION_TYPE_BASE
|
||||
for PNG 1.0)
|
||||
interlace_type - (PNG_INTERLACE_TYPE_NONE or
|
||||
PNG_INTERLACE_TYPE_ADAM7)
|
||||
interlace_type - (PNG_INTERLACE_NONE or
|
||||
PNG_INTERLACE_ADAM7)
|
||||
Any or all of interlace_type, compression_type, of
|
||||
filter_type can be
|
||||
NULL if you are not interested in their values.
|
||||
@@ -982,7 +658,7 @@ Functions are used to get the information from the info_ptr:
|
||||
signature - holds the signature read from the
|
||||
file (if any). The data is kept in
|
||||
the same offset it would be if the
|
||||
whole signature were read (ie if an
|
||||
whole signature were read (i.e. if an
|
||||
application had already read in 4
|
||||
bytes of signature before starting
|
||||
libpng, the remaining 4 bytes would
|
||||
@@ -1084,12 +760,16 @@ into the info_ptr is returned for any complex types.
|
||||
x direction
|
||||
res_y - pixels/unit physical resolution in
|
||||
x direction
|
||||
unit_type - PNG_RESOLUTION_UNKOWN,
|
||||
unit_type - PNG_RESOLUTION_UNKNOWN,
|
||||
PNG_RESOLUTION_METER
|
||||
|
||||
The data from the pHYs chunk can be retrieved in several convenient
|
||||
forms:
|
||||
|
||||
res_x = png_get_x_pixels_per_meter(png_ptr,
|
||||
info_ptr)
|
||||
res_y = png_get_y_pixels_per_meter(png_ptr,
|
||||
info_ptr)
|
||||
res_x_and_y = png_get_pixels_per_meter(png_ptr,
|
||||
info_ptr)
|
||||
aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
|
||||
@@ -1132,7 +812,7 @@ ways to transform the data will be described in the order that they
|
||||
should occur. This is important, as some of these change the color
|
||||
type and/or bit depth of the data, and some others only work on
|
||||
certain color types and bit depths. Even though each transformation
|
||||
checks to see if it has data that it can do somthing with, you should
|
||||
checks to see if it has data that it can do something with, you should
|
||||
make sure to only enable a transformation if it will be valid for the
|
||||
data. For example, don't swap red and blue on grayscale data.
|
||||
|
||||
@@ -1204,7 +884,7 @@ values of the pixels:
|
||||
|
||||
PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels
|
||||
stored in a PNG image have been "scaled" or "shifted" up to the next
|
||||
higher possible bit depth (eg from 5 bits/sample in the range [0,31] to
|
||||
higher possible bit depth (e.g. from 5 bits/sample in the range [0,31] to
|
||||
8 bits/sample in the range [0, 255]). However, it is also possible to
|
||||
convert the PNG pixel data back to the original bit depth of the image.
|
||||
This call reduces the pixels back down to the original bit depth:
|
||||
@@ -1278,8 +958,8 @@ the overall gamma correction required to produce pleasing results,
|
||||
which depends on the lighting conditions in the surrounding environment.
|
||||
Screen_gamma is display_gamma/viewing_gamma, where viewing_gamma is
|
||||
the amount of additional gamma correction needed to compensate for
|
||||
a dim (viewing_gamma=1.125) or dark (viewing_gamma=1.25) environment.
|
||||
In a brightly lit room, no compensation other than the display_gamma
|
||||
a dark (viewing_gamma=1.25) environment.
|
||||
In a dim or brightly lit room, no compensation other than the display_gamma
|
||||
is needed (viewing_gamma=1.0).
|
||||
|
||||
if (/* We have a user-defined screen
|
||||
@@ -1297,10 +977,8 @@ is needed (viewing_gamma=1.0).
|
||||
/* If we don't have another value */
|
||||
else
|
||||
{
|
||||
screen_gamma = 2.5; /* A good guess for a
|
||||
PC monitor in a bright office */
|
||||
screen_gamma = 2.2; /* A good guess for a
|
||||
PC monitor in a dim room */
|
||||
PC monitor in a bright office or a dim room */
|
||||
screen_gamma = 2.0; /* A good guess for a
|
||||
PC monitor in a dark room */
|
||||
screen_gamma = 1.7 or 1.0; /* A good
|
||||
@@ -1363,8 +1041,8 @@ zero):
|
||||
png_set_invert_mono(png_ptr);
|
||||
|
||||
PNG files store 16 bit pixels in network byte order (big-endian,
|
||||
ie. most significant bits first). This code chages the storage to the
|
||||
other way (little-endian, ie. least significant bits first, eg. the
|
||||
ie. most significant bits first). This code changes the storage to the
|
||||
other way (little-endian, i.e. least significant bits first, the
|
||||
way PCs store them):
|
||||
|
||||
if (bit_depth == 16)
|
||||
@@ -1420,7 +1098,7 @@ You can point to void or char or whatever you use for pixels.
|
||||
|
||||
If you don't want to read in the whole image at once, you can
|
||||
use png_read_rows() instead. If there is no interlacing (check
|
||||
interlace_type == PNG_INTERLACE_TYPE_NONE), this is simple:
|
||||
interlace_type == PNG_INTERLACE_NONE), this is simple:
|
||||
|
||||
png_read_rows(png_ptr, row_pointers, NULL,
|
||||
number_of_rows);
|
||||
@@ -1435,7 +1113,7 @@ row_pointers:
|
||||
|
||||
If the file is interlaced (info_ptr->interlace_type != 0), things get
|
||||
somewhat harder. The only current (PNG Specification version 1.0)
|
||||
interlacing type for PNG is (interlace_type == PNG_INTERLACE_TYPE_ADAM7)
|
||||
interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7)
|
||||
is a somewhat complicated 2D interlace scheme, known as Adam7, that
|
||||
breaks down an image into seven smaller images of varying size, based
|
||||
on an 8x8 grid.
|
||||
@@ -1474,7 +1152,7 @@ numbered scanlines. Phew!
|
||||
If you want libpng to expand the images, call this before calling
|
||||
png_start_read_image() or png_read_update_info():
|
||||
|
||||
if (interlace_type == PNG_INTERLACE_TYPE_ADAM7)
|
||||
if (interlace_type == PNG_INTERLACE_ADAM7)
|
||||
number_of_passes
|
||||
= png_set_interlace_handling(png_ptr);
|
||||
|
||||
@@ -1692,7 +1370,7 @@ png_infop info_ptr;
|
||||
|
||||
|
||||
|
||||
IV. Writing
|
||||
.SH IV. Writing
|
||||
|
||||
Much of this is very similar to reading. However, everything of
|
||||
importance is repeated here, so you won't have to constantly look
|
||||
@@ -1764,7 +1442,8 @@ have no special needs in this area, let the library do what it wants by
|
||||
not calling this function at all, as it has been tuned to deliver a good
|
||||
speed/compression ratio. The second parameter to png_set_filter() is
|
||||
the filter method, for which the only valid value is '0' (as of the
|
||||
06/96 PNG specification. The third parameter is a flag that indicates
|
||||
October 1996 PNG specification, version 1.0). The third parameter is a
|
||||
flag that indicates
|
||||
which filter type(s) are to be tested for each scanline. See the
|
||||
Compression Library for details on the specific filter types.
|
||||
|
||||
@@ -1835,8 +1514,8 @@ Some of the more important parts of the png_info are:
|
||||
PNG_COLOR_MASK_COLOR
|
||||
PNG_COLOR_MASK_ALPHA
|
||||
|
||||
interlace_type - PNG_INTERLACE_TYPE_NONE or
|
||||
PNG_INTERLACE_TYPE_ADAM7
|
||||
interlace_type - PNG_INTERLACE_NONE or
|
||||
PNG_INTERLACE_ADAM7
|
||||
compression_type - (must be
|
||||
PNG_COMPRESSION_TYPE_DEFAULT)
|
||||
filter_type - (must be PNG_FILTER_TYPE_DEFAULT)
|
||||
@@ -1933,7 +1612,7 @@ Some of the more important parts of the png_info are:
|
||||
in x direction
|
||||
res_y - pixels/unit physical resolution
|
||||
in y direction
|
||||
unit_type - PNG_RESOLUTION_UNKOWN,
|
||||
unit_type - PNG_RESOLUTION_UNKNOWN,
|
||||
PNG_RESOLUTION_METER
|
||||
|
||||
In PNG files, the alpha channel in an image is the level of opacity.
|
||||
@@ -1974,7 +1653,7 @@ The keywords that are given in the PNG Specification are:
|
||||
Description Description of image (possibly long)
|
||||
Copyright Copyright notice
|
||||
Creation Time Time of original image creation
|
||||
(usually RFC 1123 format, see below)
|
||||
(usually RFC 1123 format, see below)
|
||||
Software Software used to create the image
|
||||
Disclaimer Legal disclaimer
|
||||
Warning Warning of nature of content
|
||||
@@ -1984,7 +1663,7 @@ The keywords that are given in the PNG Specification are:
|
||||
|
||||
The keyword-text pairs work like this. Keywords should be short
|
||||
simple descriptions of what the comment is about. Some typical
|
||||
keywords are found in the PNG specification, as is some recomendations
|
||||
keywords are found in the PNG specification, as is some recommendations
|
||||
on keywords. You can repeat keywords in a file. You can even write
|
||||
some text before the image and some after. For example, you may want
|
||||
to put a description of the image before the image, but leave the
|
||||
@@ -2008,7 +1687,7 @@ time_t routine uses gmtime(). You don't have to use either of
|
||||
these, but if you wish to fill in the png_time structure directly,
|
||||
you should provide the time in universal time (GMT) if possible
|
||||
instead of your local time. Note that the year number is the full
|
||||
year (ie 1996, rather than 96 - PNG is year 2000 compliant!), and
|
||||
year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and
|
||||
that months start with 1.
|
||||
|
||||
If you want to store the time of the original image creation, you should
|
||||
@@ -2018,7 +1697,7 @@ depending on whether you mean the PNG file, the time the image was
|
||||
created in a non-PNG format, a still photo from which the image was
|
||||
scanned, or possibly the subject matter itself. In order to facilitate
|
||||
machine-readable dates, it is recommended that the "Creation Time"
|
||||
tEXt chunk use RFC 1123 format dates (eg 22 May 1997 18:07:10 GMT"),
|
||||
tEXt chunk use RFC 1123 format dates (e.g. 22 May 1997 18:07:10 GMT"),
|
||||
although this isn't a requirement. Unlike the tIME chunk, the
|
||||
"Creation Time" tEXt chunk is not expected to be automatically changed
|
||||
by the software. To facilitate the use of RFC 1123 dates, a function
|
||||
@@ -2036,7 +1715,7 @@ ways to transform the data will be described in the order that they
|
||||
should occur. This is important, as some of these change the color
|
||||
type and/or bit depth of the data, and some others only work on
|
||||
certain color types and bit depths. Even though each transformation
|
||||
checks to see if it has data that it can do somthing with, you should
|
||||
checks to see if it has data that it can do something with, you should
|
||||
make sure to only enable a transformation if it will be valid for the
|
||||
data. For example, don't swap red and blue on grayscale data.
|
||||
|
||||
@@ -2079,7 +1758,7 @@ file so that decoders can get the original data if desired.
|
||||
png_set_sBIT(png_ptr, info_ptr, &sig_bit);
|
||||
|
||||
If the data is stored in the row buffer in a bit depth other than
|
||||
one supported by PNG (ie 3 bit data in the range 0-7 for a 4-bit PNG),
|
||||
one supported by PNG (e.g. 3 bit data in the range 0-7 for a 4-bit PNG),
|
||||
this will scale the values to appear to be the correct bit depth as
|
||||
is required by PNG.
|
||||
|
||||
@@ -2087,8 +1766,8 @@ is required by PNG.
|
||||
|
||||
PNG files store 16 bit pixels in network byte order (big-endian,
|
||||
ie. most significant bits first). This code would be used if they are
|
||||
supplied the other way (little-endian, ie. least significant bits
|
||||
first, eg. the way PCs store them):
|
||||
supplied the other way (little-endian, i.e. least significant bits
|
||||
first, the way PCs store them):
|
||||
|
||||
if (bit_depth > 8)
|
||||
png_set_swap(png_ptr);
|
||||
@@ -2125,9 +1804,9 @@ Note that the distance between rows is from the last time png_write_flush()
|
||||
was called, or the first row of the image if it has never been called.
|
||||
So if you write 50 lines, and then png_set_flush 25, it will flush the
|
||||
output on the next scanline, and every 25 lines thereafter, unless
|
||||
png_write_flush()ls is called before 25 more lines have been written.
|
||||
png_write_flush() is called before 25 more lines have been written.
|
||||
If nrows is too small (less than about 10 lines for a 640 pixel wide
|
||||
RGB image) the image compression may decrease noticably (although this
|
||||
RGB image) the image compression may decrease noticeably (although this
|
||||
may be acceptable for real-time applications). Infrequent flushing will
|
||||
only degrade the compression performance by a few percent over images
|
||||
that do not use flushing.
|
||||
@@ -2165,9 +1844,9 @@ row_pointers:
|
||||
png_write_row(png_ptr, &row_pointer);
|
||||
|
||||
When the file is interlaced, things can get a good deal more
|
||||
complicated. The only currently (as of 6/96 -- PNG Specification
|
||||
version 1.0) defined interlacing scheme for PNG files is a
|
||||
compilcated interlace scheme, known as Adam7, that breaks down an
|
||||
complicated. The only currently (as of February 1998 -- PNG Specification
|
||||
version 1.0, dated October 1996) defined interlacing scheme for PNG files
|
||||
is the "Adam7" interlace scheme, that breaks down an
|
||||
image into seven smaller images of varying size. libpng will build
|
||||
these images for you, or you can do them yourself. If you want to
|
||||
build them yourself, see the PNG specification for details of which
|
||||
@@ -2212,7 +1891,7 @@ palette, or histogram, before the call to png_destroy_write_struct();
|
||||
For a more compact example of writing a PNG image, see the file example.c.
|
||||
|
||||
|
||||
V. Modifying/Customizing libpng:
|
||||
.SH V. Modifying/Customizing libpng:
|
||||
|
||||
There are two issues here. The first is changing how libpng does
|
||||
standard things like memory allocation, input/output, and error handling.
|
||||
@@ -2220,9 +1899,9 @@ The second deals with more complicated things like adding new chunks,
|
||||
adding new transformations, and generally changing how libpng works.
|
||||
|
||||
All of the memory allocation, input/output, and error handling in libpng
|
||||
goes through callbacks which are user setable. The default routines are
|
||||
goes through callbacks which are user settable. The default routines are
|
||||
in pngmem.c, pngrio.c, pngwio.c, and pngerror.c respectively. To change
|
||||
these functions, call the approprate png_set_???_fn() function.
|
||||
these functions, call the appropriate png_set_???_fn() function.
|
||||
|
||||
Memory allocation is done through the functions png_large_malloc(),
|
||||
png_malloc(), png_realloc(), png_large_free(), and png_free(). These
|
||||
@@ -2320,11 +1999,11 @@ can be found in the comments inside the code itself.
|
||||
Configuring for 16 bit platforms:
|
||||
|
||||
You may need to change the png_large_malloc() and png_large_free()
|
||||
routines in pngmem.c, as these are requred to allocate 64K, although
|
||||
routines in pngmem.c, as these are required to allocate 64K, although
|
||||
there is already support for many of the common DOS compilers. Also,
|
||||
you will want to look into zconf.h to tell zlib (and thus libpng) that
|
||||
it cannot allocate more then 64K at a time. Even if you can, the memory
|
||||
won't be accessable. So limit zlib and libpng to 64K by defining MAXSEG_64K.
|
||||
won't be accessible. So limit zlib and libpng to 64K by defining MAXSEG_64K.
|
||||
|
||||
Configuring for DOS:
|
||||
|
||||
@@ -2349,7 +2028,7 @@ You will need to write new error and warning functions that use the GUI
|
||||
interface, as described previously, and set them to be the error and
|
||||
warning functions at the time that png_create_???_struct() is called,
|
||||
in order to have them available during the structure initialization.
|
||||
They can be changed later via png_set_error_fn(). On some compliers,
|
||||
They can be changed later via png_set_error_fn(). On some compilers,
|
||||
you may also have to change the memory allocators (png_malloc, etc.).
|
||||
|
||||
Configuring for compiler xxx:
|
||||
@@ -2451,7 +2130,7 @@ to be considered when selecting row filters. This means that filters
|
||||
with higher costs are less likely to be chosen over filters with lower
|
||||
costs, unless their "sum of absolute differences" is that much smaller.
|
||||
The costs do not necessarily reflect the exact computational speeds of
|
||||
the various filters, since this would unduely influence the final image
|
||||
the various filters, since this would unduly influence the final image
|
||||
size.
|
||||
|
||||
Note that the numbers above were invented purely for this example and
|
||||
@@ -2550,7 +2229,7 @@ the first widely used release:
|
||||
0.99 0.99 2.0.99
|
||||
0.99a 0.99 2.0.99
|
||||
0.99b 0.99 2.0.99
|
||||
0.99d 0.99 2.0.99
|
||||
0.99e 0.99 2.0.99
|
||||
1.0 1.00 2.1.0
|
||||
|
||||
Henceforth the source version will match the shared-library minor
|
||||
@@ -2558,11 +2237,14 @@ and patch numbers; the shared-library major version number will be
|
||||
used for changes in backward compatibility, as it is intended.
|
||||
|
||||
.SH "SEE ALSO"
|
||||
libpngpf(3), png(5)
|
||||
.LP
|
||||
.IR libpng :
|
||||
.IP
|
||||
ftp://ftp.uu.net/graphics/png
|
||||
http://www.cdrom.com/pub/png
|
||||
|
||||
.LP
|
||||
.IR zlib :
|
||||
.IP
|
||||
(generally) at the same location as
|
||||
@@ -2573,8 +2255,8 @@ ftp://ftp.uu.net/pub/archiving/zip/zlib
|
||||
.br
|
||||
http://www.cdrom.com/pub/infozip/zlib
|
||||
|
||||
PNG specification:
|
||||
RFC 2083
|
||||
.LP
|
||||
.IR PNG specification: RFC 2083
|
||||
.IP
|
||||
(generally) at the same location as
|
||||
.I libpng
|
||||
@@ -2586,6 +2268,7 @@ or (as a W3C Recommendation) at
|
||||
.br
|
||||
http://www.w3.org/TR/REC-png.html
|
||||
|
||||
.LP
|
||||
In the case of any inconsistency between the PNG specification
|
||||
and this library, the specification takes precedence.
|
||||
|
||||
@@ -2595,7 +2278,8 @@ This man page: Glenn Randers-Pehrson
|
||||
|
||||
Contributing Authors: John Bowler, Kevin Bracey, Sam Bushell, Andreas Dilger,
|
||||
Magnus Holmgren, Tom Lane, Dave Martindale, Glenn Randers-Pehrson,
|
||||
Greg Roelofs, Guy Eric Schalnat, Paul Schmidt, Tom Tanner, Tim Wegner.
|
||||
Greg Roelofs, Guy Eric Schalnat, Paul Schmidt, Tom Tanner, Willem van
|
||||
Schaik, Tim Wegner.
|
||||
<png-implement@dworkin.wustl.edu>
|
||||
|
||||
The contributing authors would like to thank all those who helped
|
||||
@@ -2604,7 +2288,7 @@ possible without all of you.
|
||||
|
||||
Thanks to Frank J. T. Wojcik for helping with the documentation.
|
||||
|
||||
Libpng version 0.99d (February 8, 1998):
|
||||
Libpng version 0.99e (February 28, 1998):
|
||||
Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
|
||||
Currently maintained by Glenn Randers-Pehrson (randeg@alumni.rpi.edu).
|
||||
|
||||
|
||||
Reference in New Issue
Block a user