3 [authors [Henning, Christian] ]
4 [copyright 2013 Christian Henning]
6 An generic, user-friendly interface for reading and writing different image formats.
9 [dirname gil/extension/io_new]
11 Distributed under the Boost Software License, Version 1.0.
12 (See accompanying file LICENSE_1_0.txt or copy at
13 [@http://www.boost.org/LICENSE_1_0.txt])
18 [def _BMP_Wiki_ [@http://en.wikipedia.org/wiki/BMP_file_format]]
19 [def _JPEG_Wiki_ [@http://en.wikipedia.org/wiki/JPEG]]
20 [def _JPEG_lib_ [@http://www.ijg.org/]]
21 [def _PNG_Wiki_ [@http://en.wikipedia.org/wiki/Portable_Network_Graphics]]
22 [def _PNG_Lib_ [@http://libpng.org/pub/png/libpng.html]]
23 [def _PNM_Wiki_ [@http://en.wikipedia.org/wiki/Portable_anymap]]
24 [def _RAW_Wiki_ [@http://en.wikipedia.org/wiki/Raw_image_format]]
25 [def _TARGA_Wiki [@http://en.wikipedia.org/wiki/Truevision_TGA]]
26 [def _RAW_lib_ [@http://www.libraw.org/]]
27 [def _RAW_Wiki_ [@http://en.wikipedia.org/wiki/Raw_image_format]]
28 [def _TIFF_Wiki_ [@http://en.wikipedia.org/wiki/Tagged_Image_File_Format]]
29 [def _TIFF_Lib_ [@http://www.remotesensing.org/libtiff/]]
30 [def _TIFF_Base_Tags_ [@http://www.awaresystems.be/imaging/tiff/tifftags/baseline.html]]
31 [def _TIFF_Extension_Tags_ [@http://www.awaresystems.be/imaging/tiff/tifftags/extension.html]]
33 [def _BMP_TEST_FILES [@http://entropymine.com/jason/bmpsuite/]]
34 [def _PNG_TEST_FILES [@http://www.schaik.com/pngsuite/pngsuite.html]]
35 [def _TARGA_TEST_FILES [@http://www.fileformat.info/format/tga/sample/index.htm]]
36 [def _TIFF_LIB_TIFF_TEST_FILES [@http://www.remotesensing.org/libtiff/images.html]]
37 [def _TIFF_GRAPHICSMAGICK_TEST_FILES [@ftp://ftp.graphicsmagick.org/pub/tiff-samples/tiff-sample-images-be.tar.gz]]
40 This extension to boost::gil provides an easy to use interface for reading and writing
41 various image formats. It also includes a framework for adding new formats.
43 Please see section 3.3 for all supported image formats. A basic tutorial is provided
44 in section [link gil.io.tutorial Tutorial]. Also, this extension requires Boost version 1.42 and up. Furthermore the gil
45 extension Toolbox is used.
47 For adding new image formats please refer to section [link gil.io.using_io.extending_gil__io_with_new_formats Extending GIL::IO with new Formats].
48 [h2 Supported Platforms]
49 All platforms supported by boost which have a decent C++ compiler. Depending on the
50 image format one or more of the following image libraries might be needed:
58 The library is designed to support as many formats as required by the user.
59 For instance, if the user only needs bmp support none of the above mentioned
60 dependencies are required.
62 There are more details available in this documentation on the image format dependencies.
63 Please see section [link gil.io.using_io.supported_image_formats Supported Image Formats].
67 Thanks to modern C++ programming techniques the interface for this library
68 is rather small and easy to use. In this tutorial I'll give you a short walk-around
69 on how to use this boost::gil extension. For more details please refer to section 3.
71 Since this is an extension to boost::gil I expect the user to have some very basic
72 understanding of the gil ( generic image library ). Please see here for the help.
75 The header files to be included all have the same format. For instance, tiff_all.hpp will
76 allow to read and write. Whereas, tiff_read.hpp only allows for reading. If the user only
77 wants to write jpeg's include jpeg_write.hpp. All formats provide these three types of header files:
83 xxx stands for image format.
86 Probably the most common case to read a tiff image can be done as follows:
88 std::string filename( "image.tif" );
90 read_image( filename, img, tiff_tag() );
92 The code would be same for all other image formats. The only thing that needs to
93 change is the tag type ( tiff_tag ) in the read_image call.
94 The read_image() expects the supplied image type to be compatible with the
95 image stored in the file. If the user doesn't know what format an image has he/she
96 can use read_and_convert_image().
97 Another important fact is that read_image() will allocate the appropriate
98 memory needed for the read operation. There are read_view or read_and_convert_view
99 counterparts, if the memory is already allocated.
101 Sometimes the user only wants to read a sub-part of an image, then the above call
102 would look as follows:
106 , image_read_settings< tiff_tag >( point_t( 0, 0 ), point_t( 50, 50 ) )
109 The image_read_settings class will provide the user with image format independent
110 reading setting but can also serves as a pointer for format dependent settings. Please
111 see the specific image format sections [link gil.io.using_io.supported_image_formats Supported Image Formats] for more details.
113 [h2 Writing An Image]
114 Besides reading the information also writing is the second part of this boost::gil extension.
115 Writing is a lot simpler than reading since an existing image view contains all the information.
116 For instance writing an image can be done as follows:
118 std::string filename( "image.tif" );
119 rgb8_image_t img( 640, 480 );
121 // write data into image
129 The interface is similar to reading an image. To add image format specific parameter the user can use
130 image_write_info class. For instance, a user can specify the jpeg quality when writing like this:
132 std::string filename( "image.jpg" );
133 rgb8_image_t img( 640, 480 );
135 // write data into image
139 , image_write_info< jpeg_tag >( 95 )
143 The above example will write an image where the jpeg quality is set to 95 percent.
145 [h2 Reading And Writing In-Memory Buffers]
146 Reading and writing in-memory buffers are supported as well. See as follows:
149 ifstream in( "test.tif", ios::binary );
152 read_image( in, img, tiff_tag() );
154 // 2. Write image to in-memory buffer.
155 stringstream out_buffer( ios_base::out | ios_base::binary );
158 write_view( out_buffer, view( src ), tiff_tag() );
160 // 3. Copy in-memory buffer to another.
161 stringstream in_buffer( ios_base::in | ios_base::binary );
162 in_buffer << out_buffer.rdbuf();
164 // 4. Read in-memory buffer to gil image
166 read_image( in_buffer, dst, tag_t() );
168 // 5. Write out image.
169 string filename( "out.tif" );
170 ofstream out( filename.c_str(), ios_base::binary );
171 write_view( out, view( dst ), tiff_tag() );
173 In case the user is using his own stream classes he has to make sure it has the common interface read,
174 write, seek, close, etc. Interface.
178 [section:using_io Using IO]
179 [h2 General Overview]
180 The tutorial pointed out some use cases for reading and writing images in various image formats. This section will provide a more thorough overview.
182 The next sections will introduce the Read and Write interface. But it might be worth poiting out that by using some advanced metaprogramming techniques
183 the interface is rather small and hopefully easy to understand.
185 Besides the general interface the user also has the ability to interface directly with the underlying image format. For that each reader or writer
186 provides access to the so-called backend. For instance:
188 typedef get_reader_backend< const std::string
192 backend_t backend = read_image_info( bmp_filename
196 BOOST_CHECK_EQUAL( backend._info._width , 127 );
197 BOOST_CHECK_EQUAL( backend._info._height, 64 );
199 Of course, the typedef can be removed when using c++11's auto feature.
202 As the Tutorial demonstrated there are a few ways to read images. Here is an enumeration of
203 all read functions with a short description:
205 * read_image - read into a gil image with no conversion. Memory is allocated.
206 * read_view - read into a gil view with no conversion.
207 * read_and_convert_image - read and convert into a gil image. Memory is allocated.
208 * read_and_convert_view - read and convert into a gil view.
209 * read_image_info - read the image header.
211 Conversion in this context is necessary if the source ( file ) has an incompatible color space
212 with the destination ( gil image type ). If that's the case the user has to use the xxx_and_convert_xxx
215 All functions take the filename or a device as the first parameter. The filename can be anything from
216 a c string, std::string, std::wstring, and a boost::filesystem path. When using the path object the
217 user needs to define the ADD_FS_PATH_SUPPORT compiler symbol to include the boost::filesystem
218 dependency. Devices could be a FILE*, std::ifstream, and a TIFF* for TIFF images.
220 The second parameter is either an image or view type depending on the read_xxx function.
221 The third and last parameter is either an instance of the image_read_settings<FormatTag> or just the
222 FormatTag. The settings can be various depending on the format which is being read. But the all
223 share settings for reading a partial image area. The first point describes the top left image
224 coordinate whereas the second are the dimensions in x and y directions. Here an example of
225 setting up partial read.
229 , image_read_settings< tiff_tag >( point_t( 0, 0 ), point_t( 50, 50 ) )
232 Each format supports reading just the header information, using read_image_info(). Please
233 refer to the format specific sections under 3.3. A basic example follows:
235 image_read_info< tiff_t > info = read_image_info( filename
239 GIL also comes with a dynamic image extension. In the context of GIL.IO a user can define an any_image type based
240 on several image types. The IO extension would then pick the matching image type to the current image file.
241 The following example shows this feature:
243 typedef mpl::vector< gray8_image_t
249 any_image< my_img_types > runtime_image;
257 During the review it became clear that there is a need to read big images scanline by scanline. To support such use case
258 a scanline_reader is implemented for all supported image formats. The scanline_read_iterators will then allow to traverse
259 through the image. The following code sample shows the usage:
261 typedef tiff_tag tag_t;
263 typedef scanline_reader< typename get_read_device< const char*
269 reader_t reader = make_scanline_reader( "C:/boost/libs/gil/io/test_images/tiff/test.tif", tag_t() );
271 typedef rgba8_image_t image_t;
273 image_t dst( reader._info._width, reader._info._height );
274 fill_pixels( view(dst), image_t::value_type() );
276 typedef reader_t::iterator_t iterator_t;
278 iterator_t it = reader.begin();
279 iterator_t end = reader.end();
281 for( int row = 0; it != end; ++it, ++row )
283 copy_pixels( interleaved_view( reader._info._width
285 , ( image_t::view_t::x_iterator ) *it
286 , reader._scanline_length
288 , subimage_view( view( dst )
291 , reader._info._width
297 There are many ways to travese an image but for as of now only by scanline is supported.
301 There is only one function for writing out images, write_view. Similar to reading the first parameter is either
302 a filename or a device. The filename can be anything from a c string, std::string, std::wstring, and a
303 boost::filesystem path. When using the path object the user needs to define the ADD_FS_PATH_SUPPORT compiler symbol
304 to include the boost::filesystem dependency. Devices could be a FILE*, std::ifstream, and a TIFF* for TIFF images.
306 The second parameter is an view object to image being written. The third and last parameter is either a tag or
307 an image_write_info< FormatTag > object containing more settings. One example for instance is the jpeg quality.
308 Refer to the format specific sections under 3.3. to have a list of all the possible settings.
310 Writing an any_image<...> is supported. See the following example:
312 typedef mpl::vector< gray8_image_t
319 any_image< my_img_types > runtime_image;
324 , view( runtime_image )
328 [h2 Compiler Symbols]
330 The following table gives an overview of all supported compiler symbols that can be set by the user:
332 [table Compiler Symbols
333 [[Symbol] [Description]]
334 [[BOOST_GIL_IO_ENABLE_GRAY_ALPHA] [Enable the color space "gray_alpha".]]
335 [[BOOST_GIL_IO_ADD_FS_PATH_SUPPORT] [Enable boost::filesystem 3.0 library.]]
336 [[BOOST_GIL_IO_PNG_FLOATING_POINT_SUPPORTED] [Use libpng in floating point mode. This symbol is incompatible with BOOST_GIL_IO_PNG_FIXED_POINT_SUPPORTED.]]
337 [[BOOST_GIL_IO_PNG_FIXED_POINT_SUPPORTED] [Use libpng in integer mode. This symbol is incompatible with BOOST_GIL_IO_PNG_FLOATING_POINT_SUPPORTED.]]
338 [[BOOST_GIL_IO_PNG_DITHERING_SUPPORTED] [Look up "dithering" in libpng manual for explanation.]]
339 [[BOOST_GIL_IO_PNG_1_4_OR_LOWER] [Allow compiling with libpng 1.4 or lower.]]
340 [[BOOST_GIL_EXTENSION_IO_JPEG_C_LIB_COMPILED_AS_CPLUSPLUS] [libjpeg is compiled as c++ lib.]]
341 [[BOOST_GIL_EXTENSION_IO_PNG_C_LIB_COMPILED_AS_CPLUSPLUS] [libpng is compiled as c++ lib.]]
342 [[BOOST_GIL_EXTENSION_IO_TIFF_C_LIB_COMPILED_AS_CPLUSPLUS] [libtiff is compiled as c++ lib.]]
343 [[BOOST_GIL_EXTENSION_IO_ZLIB_C_LIB_COMPILED_AS_CPLUSPLUS] [zlib is compiled as c++ lib.]]
344 [[BOOST_GIL_IO_TEST_ALLOW_READING_IMAGES] [Allow basic test images to be read from local hard drive. The paths can be set in paths.hpp]]
345 [[BOOST_GIL_IO_TEST_ALLOW_WRITING_IMAGES] [Allow images to be written to the local hard drive. The paths can be set in paths.hpp]]
346 [[BOOST_GIL_IO_USE_BMP_TEST_SUITE_IMAGES] [Run tests using the bmp test images suite. See _BMP_TEST_FILES]]
347 [[BOOST_GIL_IO_USE_PNG_TEST_SUITE_IMAGES] [Run tests using the png test images suite. See _PNG_TEST_FILES]]
348 [[BOOST_GIL_IO_USE_PNM_TEST_SUITE_IMAGES] [Run tests using the pnm test images suite. Send me an email for accessing the files.]]
349 [[BOOST_GIL_IO_USE_TARGA_FILEFORMAT_TEST_SUITE_IMAGES] [Run tests using the targa file format test images suite. See _TARGA_TEST_FILES]]
350 [[BOOST_GIL_IO_USE_TIFF_LIBTIFF_TEST_SUITE_IMAGES] [Run tests using the targa file format test images suite. See _TIFF_LIB_TIFF_TEST_FILES]]
351 [[BOOST_GIL_IO_USE_TIFF_GRAPHICSMAGICK_TEST_SUITE_IMAGES] [Run tests using the targa file format test images suite. See _TIFF_GRAPHICSMAGICK_TEST_FILES]]
355 [h2 Supported Image Formats]
357 For a general overview of the BMP image file format go to the following _BMP_Wiki_.
359 Please note, the code has not been tested on X Windows System variations
360 of the BMP format which are usually referred to XBM and XPM formats.
362 Here, only the MS Windows and OS/2 format is relevant.
364 Currently the code is able to read and write the following image types:
366 Read: gray1_image_t, gray4_image_t, gray8_image_t, rgb8_image_t and, rgba8_image_t
367 Write: rgb8_image_t and, rgba8_image_t
369 The lack of having an indexed image type in gil restricts the current interface to only
370 write out non-indexed images. This is subject to change soon.
373 For a general overview of the JPEG image file format go to the following _JPEG_Wiki_.
375 This jpeg extension is based on the libjpeg library which can be found here, _JPEG_Lib_.
377 All versions starting from 8x are supported.
379 The user has to make sure this library is properly installed. I strongly recommend the user
380 to build the library yourself. It could potentially save you a lot of trouble.
382 Currently the code is able to read and write the following image types:
384 Read: gray8_image_t, rgb8_image_t, cmyk8_image_t
385 Write: gray8_image_t, rgb8_image_t, cmyk8_image_t
387 Reading YCbCr or YCCK images is possible but might result in inaccuracies since both color spaces
388 aren't available yet for gil. For now these color space are read as rgb images.
389 This is subject to change soon.
392 For a general overview of the PNG image file format go to the following _PNG_Wiki_.
394 This png extension is based on the libpng, which can be found here, _PNG_Lib.
396 All versions starting from 1.5.x are supported.
398 The user has to make sure this library is properly installed. I strongly recommend the user
399 to build the library yourself. It could potentially save you a lot of trouble.
401 Currently the code is able to read and write the following image types:
403 Read: gray1, gray2, gray4, gray8, gray16, gray_alpha_8, gray_alpha_16, rgb8, rgb16, rgba8, rgba16
404 Write: gray1, gray2, gray4, gray8, gray16, gray_alpha_8, gray_alpha_16, rgb8, rgb16, rgba8, rgba16
406 For reading gray_alpha images the user has to enable the ENABLE_GRAY_ALPHA compiler switch. This color
407 space is defined in the toolbox by using gray_alpha.hpp.
410 For a general overview of the PNM image file format go to the following _PNM_Wiki_.
412 No external library is needed for the pnm format. Both ascii and binary formats are supported.
414 Currently the code is able to read and write the following image types:
416 Read: gray1, gray8, rgb8
417 Write: gray1, gray8, rgb8
419 When reading a mono text image the data is read as a gray8 image.
422 For a general overview see _RAW_Wiki.
424 Currently the extension is only able to read rgb8 images.
427 For a general overview of the BMP image file format go to the following _TARGA_Wiki_.
429 Currently the code is able to read and write the following image types:
431 Read: rgb8_image_t and rgba8_image_t
432 Write: rgb8_image_t and rgba8_image_t
434 The lack of having an indexed image type in gil restricts the current interface to only
435 write out non-indexed images. This is subject to change soon.
438 For a general overview of the TIFF image file format go to the following _TIFF_Wiki_.
440 This tiff extension is based on the libtiff, which can be found, _TIFF_Lib_.
442 All versions starting from 3.9.x are supported.
444 The user has to make sure this library is properly installed. I strongly recommend the user
445 to build the library yourself. It could potentially save you a lot of trouble.
447 TIFF images can virtually encode all kinds of channel sizes representing various color spaces. Even
448 planar images are possible. For instance, rbg323 or gray7. The channels also can have specific formats, like
449 integer values or floating point values. For a complete set of options please consult the following websites:
452 * _TIFF_Extension_Tags_
454 The author of this extension is not claiming all tiff formats are supported. This extension is
455 likely to be a moving target adding new features with each new milestone. Here is an incomplete lists:
457 * Multi-page tiffs - read only
458 * Strip tiffs - read and write support
459 * Tiled tiffs - read and write support with user defined tiled sizes
460 * bit images tiffs - fully supported, like gray1_image_t ( minisblack )
461 * planar tiffs - fully supported
462 * floating point tiffs - fully supported
463 * palette tiffs - supported but no indexed image type is available as of now
465 This gil extension uses two different test image suites to test read and write capabilities. See test_image folder.
466 It's advisable to use ImageMagick's test viewer to display images.
469 [h2 Extending GIL::IO with new Formats]
470 Extending the gil::io with new formats is meant to be simple and straightforward. Before adding I would
471 recommend to have a look at existing implementations and then trying to follow a couple of guidelines:
473 * Create the following files for your new xxx format
474 * xxx_read.hpp // Only includes read code
475 * xxx_write.hpp // Only includes write code
476 * xxx_all.hpp // includes xxx_read.hpp and xxx_write.hpp
477 * Add the code to the boost::gil::detail namespace
478 * Create a tag type for the new format. Like this:
480 struct xxx_tag : format_tag {};
483 * Create the image_read_info for the new format. It contains all the information that are
484 necessary to read an image. It should be filled and returned by the get_info() member of
485 the reader class. See below.
487 template<> struct image_read_info< xxx_tag > {};
490 * Create the image_write_info for the new format. It contains all the information that are
491 necessary to write an image.
493 template<> struct image_write_info< xxx_tag > {};
496 * Use the following reader skeleton as a start:
498 template< typename Device
499 , typename ConversionPolicy
505 : public reader_base< xxx_tag
511 typedef typename ConversionPolicy::color_converter_type cc_t;
515 reader( Device& device )
519 reader( Device& device
523 , reader_base< xxx_tag
528 image_read_info< xxx_tag > get_info()
530 // your implementation here
533 template< typename View >
534 void apply( const View& dst_view )
536 // your implementation here
541 * The writer skeleton:
543 template< typename Device >
550 writer( Device & file )
554 template<typename View>
555 void apply( const View& view )
557 // your implementation here
560 template<typename View>
561 void apply( const View& view
562 , const image_write_info< xxx_tag >& info )
564 // your implementation here
571 [section Running gil::io tests]
572 gil::io comes with a large suite of test cases which reads and writes various file formats. It uses some test image suites which can be found online or which can be demanded from me by sending me an email.
574 There are some test images created by me in the test folder. To enable unit tests which make use of them set the following compiler options BOOST_GIL_IO_TEST_ALLOW_READING_IMAGES and BOOST_GIL_IO_TEST_ALLOW_WRITING_IMAGES.
576 The following list provides all links to the image suites the compiler symbol to enable the tests:
578 * BMP: _BMP_TEST_FILES -- BOOST_GIL_IO_USE_BMP_TEST_SUITE_IMAGES
579 * PNG: _PNG_TEST_FILES -- BOOST_GIL_IO_USE_PNG_TEST_SUITE_IMAGES
580 * PNM: request files from me -- BOOST_GIL_IO_USE_PNM_TEST_SUITE_IMAGES
581 * TARGA: _TARGA_TEST_FILES -- BOOST_GIL_IO_USE_TARGA_FILEFORMAT_TEST_SUITE_IMAGES
582 * TIFF: _TIFF_LIB_TIFF_TEST_FILES -- BOOST_GIL_IO_USE_TIFF_LIBTIFF_TEST_SUITE_IMAGES
583 * TIFF _TIFF_GRAPHICSMAGICK_TEST_FILES -- BOOST_GIL_IO_USE_TIFF_GRAPHICSMAGICK_TEST_SUITE_IMAGES