git.saurik.com Git - wxWidgets.git/blame - src/tiff/contrib/addtiffo/README

Commit	Line	Data
8414a40c VZ	1	addtiffo 1.0
	2	============
	3
	4	The addtiffo utility is used to add overview pyramids to an existing
	5	TIFF or GeoTIFF file. Some applications can take advantage of these
	6	overviews to accelerate overview display performance of large rasters.
	7
	8	This release of addtiffo is primarily intended for compatibility testing
	9	with applications, and to see if there is interest in a cleaner release
	10	of the capability ... perhaps incorporation into the libtiff tools
	11	distribution.
	12
	13	Please feel free to contact me with questions, or problems.
	14
	15	warmerda@home.com
	16	http://home.gdal.org/~warmerda/
	17
	18
	19	Usage
	20	-----
	21
	22	Usage: addtiffo [-r {average/nearest} [-subifd]
	23	tiff_filename [resolution_reductions]
	24
	25	Example:
	26	% addtiffo abc.tif 2 4 8 16
	27
	28	The numeric arguments are the list of reduction factors to
	29	generate. In this example a 1/2, 1/4 1/8 and 1/16
	30
	31
	32
	33	Limitations
	34	-----------
	35
	36	See tif_overview.cpp for up to date details.
	37
	38	o Currently only images with bits_per_sample of a multiple of eight
	39	will work.
	40
	41	o The code will attempt to use the same kind of compression,
	42	photometric interpretation, and organization as the source image, but
	43	it doesn't copy geotiff tags to the reduced resolution images.
	44
	45	o Reduced resolution overviews for multi-sample files will currently
	46	always be generated as PLANARCONFIG_SEPARATE. This could be fixed
	47	reasonable easily if needed to improve compatibility with other
	48	packages. Many don't properly support PLANARCONFIG_SEPARATE.
	49
	50	o Overviews are always written as appended IFDs, rather than using the
	51	``tree of tree's'' approach using the SUBIFD tag. I wanted to implement
	52	both, but it isn't currently easy to add a SUBIFD tag to an existing
	53	main tiff IFD with libtiff. I hope to try this again later.
	54
	55
	56	TIFF File Tags
	57	--------------
	58
	59	The results of running addtiffo on a 1024x1024 tiled greyscale file
	60	with the arguments ``2 4 8 16'' is to add four additional TIFF directories
	61	appended on the file with the SUBFILETYPE flag to 0x1 indicating the extra
	62	items are reduced resolution images.
	63
	64	The tiffinfo output of such a file might look like this:
65
66	TIFF Directory at offset 0x118008
67	Image Width: 1024 Image Length: 1024
68	Tile Width: 256 Tile Length: 112
69	Bits/Sample: 8
70	Compression Scheme: none
71	Photometric Interpretation: min-is-black
72	Samples/Pixel: 1
73	Planar Configuration: single image plane
74	TIFF Directory at offset 0x15e1d2
75	Subfile Type: reduced-resolution image (1 = 0x1)
76	Image Width: 512 Image Length: 512
77	Tile Width: 256 Tile Length: 112
78	Bits/Sample: 8
79	Compression Scheme: none
80	Photometric Interpretation: min-is-black
81	Samples/Pixel: 1
82	Planar Configuration: separate image planes
83	TIFF Directory at offset 0x1732b8
84	Subfile Type: reduced-resolution image (1 = 0x1)
85	Image Width: 256 Image Length: 256
86	Tile Width: 256 Tile Length: 112
87	Bits/Sample: 8
88	Compression Scheme: none
89	Photometric Interpretation: min-is-black
90	Samples/Pixel: 1
91	Planar Configuration: separate image planes
92	TIFF Directory at offset 0x17a366
93	Subfile Type: reduced-resolution image (1 = 0x1)
94	Image Width: 128 Image Length: 128
95	Tile Width: 128 Tile Length: 112
96	Bits/Sample: 8
97	Compression Scheme: none
98	Photometric Interpretation: min-is-black
99	Samples/Pixel: 1
100	Planar Configuration: separate image planes
101	TIFF Directory at offset 0x17b40c
102	Subfile Type: reduced-resolution image (1 = 0x1)
103	Image Width: 64 Image Length: 64
104	Tile Width: 64 Tile Length: 64
105	Bits/Sample: 8
106	Compression Scheme: none
107	Photometric Interpretation: min-is-black
108	Samples/Pixel: 1
109	Planar Configuration: separate image planes
110
111
112	Building
113	--------
114
115	You will need a C compiler. You will need to have libtiff already
116	built and installed. The provided Makefile should work on most Unix systems.
117	A similar file will be needed for Windows, but is not provided.
118
119	The CFLAGS and LIBS macros in the Makefile will have to be updated to
120	point to the correct location of the libtiff include files, and library.
121
122
123	Credits
124	-------
125
126	o Intergraph Corporation for partially funding the work.
127
128	o Global Geomatics for partially funding reorganization of the overview
129	building ability as a separate utility.
130
131	o Orrin Long, and Ed Grissom of Intergraph for explaining what needed to
132	be done.
133
134	o Max Martinez of Erdas for his discussion of external overviews.
135
136	o Atlantis Scientific who supported adding averaging, and some other
137	generalizations.
138
139	o Frank Warmerdam for writing the bulk of the code.
140
141	o Sam Leffler since this only exists because of his libtiff.
142