{"id":1585,"date":"2013-11-01T15:10:51","date_gmt":"2013-11-01T14:10:51","guid":{"rendered":"https:\/\/ridgesolutions.ie\/?p=1585"},"modified":"2013-11-22T14:32:41","modified_gmt":"2013-11-22T13:32:41","slug":"write-jpeg-with-comment-boost-generic-image-library-gil","status":"publish","type":"post","link":"https:\/\/www.ridgesolutions.ie\/index.php\/2013\/11\/01\/write-jpeg-with-comment-boost-generic-image-library-gil\/","title":{"rendered":"Write jpeg with header comment – boost generic image library (gil)"},"content":{"rendered":"

I had to hack the living daylights out of something today, and although I am not proud of it, needs must where the devil drives!<\/p>\n

I was using the boost generic image library (gil) for managing some camera images and using jpeg_write_view() for saving them as JPEGs. A requirement emerged to insert a comment into the header of the saved images, but the gil does not support this out of the box.<\/p>\n

The gil uses libjpeg for writing its JPEGs and adding a comment in libjped is as easy as calling jpeg_write_marker(). The problem was that the gil buries libjpeg calls under a few classes so I had to copy and paste some of this in order to redefine a new writer which supports comments.<\/p>\n

Anyway I have included the extra code inline below, it adds a new helper function called jpeg_write_view_comment()<\/p>\n

Use this new function like this:<\/p>\n

\r\n\r\n int quality = 70;\r\n jpeg_write_view_comment(\"image1.jpg\", view, quality, \"a comment damn it!!!\");\r\n\r\n<\/pre>\n
Here is the extra code which I placed in a file called jpeg_writer_comment.h<\/p>\n
\r\n#pragma once\r\n\r\n#include \"boost\/gil\/extension\/io\/dynamic_io.hpp\"\r\n\r\nusing namespace boost;\r\nusing namespace boost::gil;\r\nusing namespace boost::gil::detail;\r\n\r\nclass jpeg_writer_comment : public file_mgr {\r\n    jpeg_compress_struct _cinfo;\r\n    jpeg_error_mgr _jerr;\r\n\r\n    void init() {\r\n        _cinfo.err=jpeg_std_error(&_jerr);\r\n        jpeg_create_compress(&_cinfo);\r\n        jpeg_stdio_dest(&_cinfo,_fp.get());\r\n    }\r\npublic:\r\n    jpeg_writer_comment(FILE* file)           : file_mgr(file)           { init(); }\r\n    jpeg_writer_comment(const char* filename) : file_mgr(filename, \"wb\") { init(); }\r\n    ~jpeg_writer_comment() { jpeg_destroy_compress(&_cinfo); }\r\n\r\n    template \r\n    void apply(const View& view,int quality=100, const char* comment = NULL) {\r\n        _cinfo.image_width  = (JDIMENSION)view.width();\r\n        _cinfo.image_height = (JDIMENSION)view.height();\r\n        _cinfo.input_components=num_channels::value;\r\n        _cinfo.in_color_space = jpeg_write_support_private::type,\r\n                                                           typename color_space_type::type>::color_type;\r\n        jpeg_set_defaults(&_cinfo);\r\n        jpeg_set_quality(&_cinfo, quality, TRUE);\r\n        jpeg_start_compress(&_cinfo, TRUE);\r\n\r\n        if (comment) {\r\n        \tjpeg_write_marker(&_cinfo, JPEG_COM, (const JOCTET*)comment, strlen(comment));\r\n        }\r\n\r\n        std::vector::type> > > row(view.width());\r\n        JSAMPLE* row_address=(JSAMPLE*)&row.front();\r\n        for (int y=0;y\r\n    void write_view(const any_image_view& runtime_view) {\r\n        dynamic_io_fnobj op(this);\r\n        apply_operation(runtime_view,op);\r\n    }\r\n};\r\n\r\n\r\n\r\ntemplate \r\ninline void jpeg_write_view_comment(const char* filename,const View& view,int quality=100, const char* comment = NULL) {\r\n    BOOST_STATIC_ASSERT(jpeg_write_support::is_supported);\r\n\r\n    jpeg_writer_comment m(filename);\r\n    m.apply(view, quality, comment);\r\n}\r\n\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
I had to hack the living daylights out of something today, and although I am not proud of it, needs must where the devil drives! I was using the boost generic image library (gil) for managing some camera images and using jpeg_write_view() for saving them as JPEGs. A requirement emerged to insert a comment into […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[228,292],"class_list":["post-1585","post","type-post","status-publish","format-standard","hentry","category-tech-stuff","tag-boost","tag-gil"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t