projs/20161018_web_page_thumbnail_make/thumbnails_make.php

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//thumbnails_make.php, v0.1a, Copyright David T. Ashley, 2016
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//Copyright 2016 David T. Ashley
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//This source code and any program in which it is compiled/used is provided under the GNU GENERAL
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//IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
//ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
//
//  16. Limitation of Liability.
//
//  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
//WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
//THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
//GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
//USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
//DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
//PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
//EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
//SUCH DAMAGES.
//
//  17. Interpretation of Sections 15 and 16.
//
//  If the disclaimer of warranty and limitation of liability provided
//above cannot be given local legal effect according to their terms,
//reviewing courts shall apply local law that most closely approximates
//an absolute waiver of all civil liability in connection with the
//Program, unless a warranty or assumption of liability accompanies a
//copy of the Program in return for a fee.
//
//                     END OF TERMS AND CONDITIONS
//
//            How to Apply These Terms to Your New Programs
//
//  If you develop a new program, and you want it to be of the greatest
//possible use to the public, the best way to achieve this is to make it
//free software which everyone can redistribute and change under these terms.
//
//  To do so, attach the following notices to the program.  It is safest
//to attach them to the start of each source file to most effectively
//state the exclusion of warranty; and each file should have at least
//the "copyright" line and a pointer to where the full notice is found.
//
//    <one line to give the program's name and a brief idea of what it does.>
//    Copyright (C) <year>  <name of author>
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU General Public License as published by
//    the Free Software Foundation, either version 3 of the License, or
//    (at your option) any later version.
//
//    This program is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU General Public License for more details.
//
//    You should have received a copy of the GNU General Public License
//    along with this program.  If not, see <http://www.gnu.org/licenses/>.
//
//Also add information on how to contact you by electronic and paper mail.
//
//  If the program does terminal interaction, make it output a short
//notice like this when it starts in an interactive mode:
//
//    <program>  Copyright (C) <year>  <name of author>
//    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
//    This is free software, and you are welcome to redistribute it
//    under certain conditions; type `show c' for details.
//
//The hypothetical commands `show w' and `show c' should show the appropriate
//parts of the General Public License.  Of course, your program's commands
//might be different; for a GUI interface, you would use an "about box".
//
//  You should also get your employer (if you work as a programmer) or school,
//if any, to sign a "copyright disclaimer" for the program, if necessary.
//For more information on this, and how to apply and follow the GNU GPL, see
//<http://www.gnu.org/licenses/>.
//
//  The GNU General Public License does not permit incorporating your program
//into proprietary programs.  If your program is a subroutine library, you
//may consider it more useful to permit linking proprietary applications with
//the library.  If this is what you want to do, use the GNU Lesser General
//Public License instead of this License.  But first, please read
//<http://www.gnu.org/philosophy/why-not-lgpl.html>.
//-------------------------------------------------------------------------------------------------
//This program, a PHP script, creates thumbnail images for recognized
//image files in the current working directory.  This program is part of a
//3-program suite designed to collectively create a web page directly from
//digital camera files (and of course the web page can be customized by
//hand-editing after it is automatically generated).  The supported process for
//creating a web page involves 3 programs (rather than 1) primarily to circumvent
//the involuntary process termination that will occur in some shared environments
//if a process consumes too much CPU time.
//
//The 3 programs in the 3-program suite are:
//
//   filenames_canonize.php:
//      Converts all names of files in a directory to lower-case, and makes
//      substitutions for any unusual characters.
//
//   thumbnails_make.php (this program):
//      Creates thumbnails from recognized image types.  The thumbnails are
//      named relative to the original image file with the suffix "_small".
//      Only 20 files are converted on each invocation of the program, to
//      avoid the involuntary process termination that typically occurs in
//      a shared hosting environment when a process uses too much CPU time.
//      The program should be run repeatedly until it indicates that it has
//      no more thumbnails to create.
//
//      If any full-sized photos are modified, any corresponding thumbnails
//      should be deleted and thumbnails_make.php and indexfile_make.php should
//      be run again.
//
//   indexfile_make.php
//      Scans a directory and makes an index file ("index2.php") displaying
//      all the thumbnail images, each of which link to the corresponding
//      full-sized image.  The index file is tailored to Dave Ashley's
//      needs, but the created file can be edited and most of the content
//      pasted into an HTML file.  To avoid the accidental loss of 
//      information, any existing "index2.php" file is renamed out of the
//      way.
//
//This script is designed to be run manually (rather than automatically invoked
//as a result of a web page request).  It was written in PHP for convenience
//simply because DreamHost (the web hosting company Dave Ashley uses) has as part
//of its hosting environment PHP with the ImageMagick library compiled in.
//
//Usually, this script is invoked using "php <path>/thumbnails_make.php", but the
//method of invocation may vary based on computing platform details.
//--------------------------------------------------------------------------------
//This program is free software: you can redistribute it and/or modify
//it under the terms of the GNU General Public License as published by
//the Free Software Foundation, either version 3 of the License, or
//(at your option) any later version.
//
//This program is distributed in the hope that it will be useful,
//but WITHOUT ANY WARRANTY; without even the implied warranty of
//MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//GNU General Public License for more details.
//
//The GNU General Public License is reproduced below, and also is 
//available at http://www.gnu.org/licenses/.
//--------------------------------------------------------------------------------
//                    GNU GENERAL PUBLIC LICENSE
//                       Version 3, 29 June 2007
//
// Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
// Everyone is permitted to copy and distribute verbatim copies
// of this license document, but changing it is not allowed.
//
//                            Preamble
//
//   The GNU General Public License is a free, copyleft license for
// software and other kinds of works.
//
//   The licenses for most software and other practical works are designed
// to take away your freedom to share and change the works.  By contrast,
// the GNU General Public License is intended to guarantee your freedom to
// share and change all versions of a program--to make sure it remains free
// software for all its users.  We, the Free Software Foundation, use the
// GNU General Public License for most of our software; it applies also to
// any other work released this way by its authors.  You can apply it to
// your programs, too.
//
//   When we speak of free software, we are referring to freedom, not
// price.  Our General Public Licenses are designed to make sure that you
// have the freedom to distribute copies of free software (and charge for
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//
//   To protect your rights, we need to prevent others from denying you
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// you modify it: responsibilities to respect the freedom of others.
//
//   For example, if you distribute copies of such a program, whether
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// freedoms that you received.  You must make sure that they, too, receive
// or can get the source code.  And you must show them these terms so they
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//
//   Developers that use the GNU GPL protect your rights with two steps:
// (1) assert copyright on the software, and (2) offer you this License
// giving you legal permission to copy, distribute and/or modify it.
//
//   For the developers' and authors' protection, the GPL clearly explains
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// authors' sake, the GPL requires that modified versions be marked as
// changed, so that their problems will not be attributed erroneously to
// authors of previous versions.
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//   Some devices are designed to deny users access to install or run
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//   Finally, every program is threatened constantly by software patents.
// States should not allow patents to restrict development and use of
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//
//   The precise terms and conditions for copying, distribution and
// modification follow.
//
//                       TERMS AND CONDITIONS
//
//   0. Definitions.
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//   "This License" refers to version 3 of the GNU General Public License.
//
//   "Copyright" also means copyright-like laws that apply to other kinds of
// works, such as semiconductor masks.
//
//   "The Program" refers to any copyrightable work licensed under this
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// "recipients" may be individuals or organizations.
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//   To "modify" a work means to copy from or adapt all or part of the work
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// exact copy.  The resulting work is called a "modified version" of the
// earlier work or a work "based on" the earlier work.
//
//   A "covered work" means either the unmodified Program or a work based
// on the Program.
//
//   To "propagate" a work means to do anything with it that, without
// permission, would make you directly or secondarily liable for
// infringement under applicable copyright law, except executing it on a
// computer or modifying a private copy.  Propagation includes copying,
// distribution (with or without modification), making available to the
// public, and in some countries other activities as well.
//
//   To "convey" a work means any kind of propagation that enables other
// parties to make or receive copies.  Mere interaction with a user through
// a computer network, with no transfer of a copy, is not conveying.
//
//   An interactive user interface displays "Appropriate Legal Notices"
// to the extent that it includes a convenient and prominently visible
// feature that (1) displays an appropriate copyright notice, and (2)
// tells the user that there is no warranty for the work (except to the
// extent that warranties are provided), that licensees may convey the
// work under this License, and how to view a copy of this License.  If
// the interface presents a list of user commands or options, such as a
// menu, a prominent item in the list meets this criterion.
//
//   1. Source Code.
//
//   The "source code" for a work means the preferred form of the work
// for making modifications to it.  "Object code" means any non-source
// form of a work.
//
//   A "Standard Interface" means an interface that either is an official
// standard defined by a recognized standards body, or, in the case of
// interfaces specified for a particular programming language, one that
// is widely used among developers working in that language.
//
//   The "System Libraries" of an executable work include anything, other
// than the work as a whole, that (a) is included in the normal form of
// packaging a Major Component, but which is not part of that Major
// Component, and (b) serves only to enable use of the work with that
// Major Component, or to implement a Standard Interface for which an
// implementation is available to the public in source code form.  A
// "Major Component", in this context, means a major essential component
// (kernel, window system, and so on) of the specific operating system
// (if any) on which the executable work runs, or a compiler used to
// produce the work, or an object code interpreter used to run it.
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//   The "Corresponding Source" for a work in object code form means all
// the source code needed to generate, install, and (for an executable
// work) run the object code and to modify the work, including scripts to
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//   The Corresponding Source need not include anything that users
// can regenerate automatically from other parts of the Corresponding
// Source.
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//   The Corresponding Source for a work in source code form is that
// same work.
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//   2. Basic Permissions.
//
//   All rights granted under this License are granted for the term of
// copyright on the Program, and are irrevocable provided the stated
// conditions are met.  This License explicitly affirms your unlimited
// permission to run the unmodified Program.  The output from running a
// covered work is covered by this License only if the output, given its
// content, constitutes a covered work.  This License acknowledges your
// rights of fair use or other equivalent, as provided by copyright law.
//
//   You may make, run and propagate covered works that you do not
// convey, without conditions so long as your license otherwise remains
// in force.  You may convey covered works to others for the sole purpose
// of having them make modifications exclusively for you, or provide you
// with facilities for running those works, provided that you comply with
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// for you must do so exclusively on your behalf, under your direction
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//   3. Protecting Users' Legal Rights From Anti-Circumvention Law.
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//   No covered work shall be deemed part of an effective technological
// measure under any applicable law fulfilling obligations under article
// 11 of the WIPO copyright treaty adopted on 20 December 1996, or
// similar laws prohibiting or restricting circumvention of such
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//   When you convey a covered work, you waive any legal power to forbid
// circumvention of technological measures to the extent such circumvention
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// modification of the work as a means of enforcing, against the work's
// users, your or third parties' legal rights to forbid circumvention of
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//   4. Conveying Verbatim Copies.
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//   You may convey verbatim copies of the Program's source code as you
// receive it, in any medium, provided that you conspicuously and
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//     "keep intact all notices".
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//   "Additional permissions" are terms that supplement the terms of this
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// sale, or importing the Program or any portion of it.
//
//   11. Patents.
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// work thus licensed is called the contributor's "contributor version".
//
//   A contributor's "essential patent claims" are all patent claims
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// but do not include claims that would be infringed only as a
// consequence of further modification of the contributor version.  For
// purposes of this definition, "control" includes the right to grant
// patent sublicenses in a manner consistent with the requirements of
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//   Each contributor grants you a non-exclusive, worldwide, royalty-free
// patent license under the contributor's essential patent claims, to
// make, use, sell, offer for sale, import and otherwise run, modify and
// propagate the contents of its contributor version.
//
//   In the following three paragraphs, a "patent license" is any express
// agreement or commitment, however denominated, not to enforce a patent
// (such as an express permission to practice a patent or covenant not to
// sue for patent infringement).  To "grant" such a patent license to a
// party means to make such an agreement or commitment not to enforce a
// patent against the party.
//
//   If you convey a covered work, knowingly relying on a patent license,
// and the Corresponding Source of the work is not available for anyone
// to copy, free of charge and under the terms of this License, through a
// publicly available network server or other readily accessible means,
// then you must either (1) cause the Corresponding Source to be so
// available, or (2) arrange to deprive yourself of the benefit of the
// patent license for this particular work, or (3) arrange, in a manner
// consistent with the requirements of this License, to extend the patent
// license to downstream recipients.  "Knowingly relying" means you have
// actual knowledge that, but for the patent license, your conveying the
// covered work in a country, or your recipient's use of the covered work
// in a country, would infringe one or more identifiable patents in that
// country that you have reason to believe are valid.
//
//   If, pursuant to or in connection with a single transaction or
// arrangement, you convey, or propagate by procuring conveyance of, a
// covered work, and grant a patent license to some of the parties
// receiving the covered work authorizing them to use, propagate, modify
// or convey a specific copy of the covered work, then the patent license
// you grant is automatically extended to all recipients of the covered
// work and works based on it.
//
//  A patent license is "discriminatory" if it does not include within
// the scope of its coverage, prohibits the exercise of, or is
// conditioned on the non-exercise of one or more of the rights that are
// specifically granted under this License.  You may not convey a covered
// work if you are a party to an arrangement with a third party that is
// in the business of distributing software, under which you make payment
// to the third party based on the extent of your activity of conveying
// the work, and under which the third party grants, to any of the
// parties who would receive the covered work from you, a discriminatory
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// conveyed by you (or copies made from those copies), or (b) primarily
// for and in connection with specific products or compilations that
// contain the covered work, unless you entered into that arrangement,
// or that patent license was granted, prior to 28 March 2007.
//
//   Nothing in this License shall be construed as excluding or limiting
// any implied license or other defenses to infringement that may
// otherwise be available to you under applicable patent law.
//
//   12. No Surrender of Others' Freedom.
//
//   If conditions are imposed on you (whether by court order, agreement or
// otherwise) that contradict the conditions of this License, they do not
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// the Program, the only way you could satisfy both those terms and this
// License would be to refrain entirely from conveying the Program.
//
//   13. Use with the GNU Affero General Public License.
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//   Notwithstanding any other provision of this License, you have
// permission to link or combine any covered work with a work licensed
// under version 3 of the GNU Affero General Public License into a single
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// section 13, concerning interaction through a network will apply to the
// combination as such.
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// be similar in spirit to the present version, but may differ in detail to
// address new problems or concerns.
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//   Each version is given a distinguishing version number.  If the
// Program specifies that a certain numbered version of the GNU General
// Public License "or any later version" applies to it, you have the
// option of following the terms and conditions either of that numbered
// version or of any later version published by the Free Software
// Foundation.  If the Program does not specify a version number of the
// GNU General Public License, you may choose any version ever published
// by the Free Software Foundation.
//
//   If the Program specifies that a proxy can decide which future
// versions of the GNU General Public License can be used, that proxy's
// public statement of acceptance of a version permanently authorizes you
// to choose that version for the Program.
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//   Later license versions may give you additional or different
// permissions.  However, no additional obligations are imposed on any
// author or copyright holder as a result of your choosing to follow a
// later version.
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//   THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
// APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
// HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
// IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
// ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
//
//   16. Limitation of Liability.
//
//   IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
// WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
// THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
// GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
// USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
// DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
// PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
// EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGES.
//
//   17. Interpretation of Sections 15 and 16.
//
//   If the disclaimer of warranty and limitation of liability provided
// above cannot be given local legal effect according to their terms,
// reviewing courts shall apply local law that most closely approximates
// an absolute waiver of all civil liability in connection with the
// Program, unless a warranty or assumption of liability accompanies a
// copy of the Program in return for a fee.
//--------------------------------------------------------------------------------
//C O N F I G U R A T I O N
//--------------------------------------------------------------------------------
//Configuration switch combinations were not tested.  E-mail me any program
//corrections (dashley@gmail.com).
define ("CFG_PROGNAME", "thumbnails_make.php");
   //Number of characters per line preferred for console output.
define ("CFG_CONSOLE_STD_LINE_LEN", 78);
   //Number of characters per line preferred for console output.
define ("CFG_THUMBNAIL_DIMENSION_MAX", 125);
   //The maximum dimension of the created thumbnails.  Thumbnails are sized so
   //that the longest dimension is this many pixels.
define ("CFG_THUMBNAIL_BEVELED_BORDER_WIDTH", 4);
   //The number of pixels that the thumbnail beveled borders should be.
define ("CFG_THUMBNAIL_FILENAME_SUFFIX", "_small");
   //String added just before the filename extension to choose thumbnail names
   //based on name of full-sized image.
define ("CFG_LANCZOS_FILTER_APPLY", FALSE);
   //TRUE if should apply the Lanczos filter when making the thumbnail, FALSE
   //otherwise.  I have no idea if using a Lanczos filter improves the quality
   //of the thumbnails, but the filter was applied in the PHP example I found
   //online.  Applying the Lanczos filter typically adds a few seconds to the
   //time required to create each thumbnail.
define ("CFG_MAX_THUMBNAILS_PER_INVOCATION", 20);
   //The maximum number of thumbnails that should be created per invocation.
   //This is to prevent the program from being involuntarily terminated
   //for taking too much CPU time.
//--------------------------------------------------------------------------------
//Calculates important integer indices related to creating a thumbnail, in order
//to minimize distortion in the thumbnail.
//
//When creating a thumbnail, the longer side may be relatively short (perhaps
//100 pixels), and the shorter side may be even shorter (perhaps even as short
//as 10 pixels).  If the dimensions of the original image were not changed,
//converting the image to a thumbnail may result in distortion of up to about
//one percent.  As an example, suppose that a 1600 x 900 image is converted to a
//thumbnail with the longer side of 125 pixels.  The ideal dimension for the
//shorter side would be (900/1600) * 125 = 70.3125 pixels.  The aspect ratio of
//the thumbnail can't be made to match the aspect ratio of the original image.
//
//To avoid any aspect ratio distortion that might be noticeable, this program
//chooses the shorter dimension for the thumbnail that is the ceiling of the actual
//quotient, then crops the longer dimension of the original image before the
//conversion to try and match the aspect ratios as closely as possible.
//
//In the example a paragraph or two above, the shorter side of the thumbnail
//would be chosen to be 71 pixels.
//
//Once this choice is made, we want to trim the original image before conversion
//so that n/900 is as close as possible to 125/71.  n = (900 * 125) / 71 = 
//1584.5070 pixels, so we choose 1585.  This keeps the aspect ratio of the 
//original image and the thumbnail as close as possible.
//
//Although the longer side of the original image may be reduced prior to the
//conversion to a thumbnail, this information is not written to disk, and
//the original image is not modified.  The adjustment of the longer side is
//just a conversion trick to hopefully get better thumbnails. 
function calc_thumbnail_conversion_pars
         (
           $in_orig_longer,
              //Longer dimension of original image.
           $in_orig_shorter,
              //Shorter dimension of original image.
           $in_thumbnail_longer,
              //Longer dimension of desired thumbnail.
         & $out_thumbnail_longer,
              //Longer dimension of thumbnail that should be created.
         & $out_thumbnail_shorter,
              //Shorter dimension of thumbnail that should be created.
         & $out_orig_crop_dim_longer,
              //The size to crop to on the longer axis of the original.
         & $out_orig_crop_dim_shorter,
              //The size to crop to on the shorter axis of the original.
         & $out_orig_crop_start_longer,
              //For use with the Imagick:cropImage() method, the start
              //position of the crop on the longer axis.
         & $out_orig_crop_start_shorter
              //For use with the Imagick:cropImage() method, the start
              //position of the crop on the shorter axis.
         )
{
   //Set the thumbnail shorter dimension to the floor.  This means would need to trim
   //longest dimension of original to match aspect ratio as closely as possible.
   $out_thumbnail_longer        = $in_thumbnail_longer;
   $out_thumbnail_shorter       = ceil(((float)$in_thumbnail_longer * 
                                  (float)$in_orig_shorter) / (float)$in_orig_longer);
   settype($out_thumbnail_shorter, "integer");

   //The aspect ratio of the thumbnail is now set.  Try to match the aspect ratio of the larger
   //image as closely as possible by selecting a smaller number for the long axis of the
   //original image.
   $out_orig_crop_dim_longer = round(((float)$in_thumbnail_longer * 
                               (float)$in_orig_shorter) / (float)$out_thumbnail_shorter);
   settype($out_orig_crop_dim_longer, "integer");

   //The original keeps its shorter dimension unchanged.
   $out_orig_crop_dim_shorter   = $in_orig_shorter;

   //Set the cropping of the longer side of the original to cover half the necessary
   //reduction.
   $out_orig_crop_start_longer  = round(((float)$in_orig_longer - 
                                  (float)$out_orig_crop_dim_longer) / 2.0);
   settype($out_orig_crop_start_longer, "integer");

   //No cropping of original shorter side.
   $out_orig_crop_start_shorter = 0;
}
//--------------------------------------------------------------------------------
//Repeats a character to the console output a certain number of times.
function rep_char_con($c, $n)
{
   while ($n--)
      echo $c;
}
//--------------------------------------------------------------------------------
//Writes a standard thick horizontal line to the console.
function hor_line_thick()
{
   rep_char_con("=", CFG_CONSOLE_STD_LINE_LEN);
   echo "\n";
}
//--------------------------------------------------------------------------------
//Writes a standard thin horizontal line to the console.
function hor_line_thin()
{
   rep_char_con("-", CFG_CONSOLE_STD_LINE_LEN);
   echo "\n";
}
//--------------------------------------------------------------------------------
//Returns an array of all files in the working directory.
//If no files can be found, returns FALSE.
function get_file_names_in_dir()
{
   //Get directory list.
   $rv = scandir (".");

   //If the list is empty, something went wrong.  Return FALSE.
   if ($rv === FALSE)
      return FALSE;

   return $rv;
}
//--------------------------------------------------------------------------------
//Returns TRUE if a file name appears to be a valid full-sized image name, 
//or FALSE otherwise.
function is_full_sized_image_file_name($in_filename)
{
   //Convert the string name to all lower case.  This will do for
   //comparisons and tests.
   $s = strtolower($s);

   //Attempt to split the name into a base and an extension.  Any failure
   //means it is an unsuitable name.
   $extension_start = strrpos($in_filename, ".");
      //Find position of last "." in string.  This should precede the
      //file extension.

   if ($extension_start === FALSE)
   {
      //Bad name.  Unsuitable.
      return FALSE;
   } 

   //Calculate the base and extension.
   $filename_base    = substr($in_filename, 0, $extension_start);
   $filename_extension = substr($in_filename, $extension_start + 1);

   //If the extension is neither "jpg" nor "jpeg", it is unsuitable.
   if (($filename_extension != "jpg") && ($filename_extension != "jpeg"))
      return FALSE;

   //If the filename base is empty, the filename is unsuitable.
   if (strlen($filename_base) == 0)
      return FALSE;

   //If the last characters of the base are the CFG_THUMBNAIL_FILENAME_SUFFIX,
   //the name is unsuitable.
   if (strlen($filename_base) >= strlen(CFG_THUMBNAIL_FILENAME_SUFFIX))
   {
      if (substr($filename_base, strlen($filename_base) - strlen(CFG_THUMBNAIL_FILENAME_SUFFIX)) 
          == CFG_THUMBNAIL_FILENAME_SUFFIX)
         return FALSE;
   }

   //Looks good.
   return TRUE;
}
//--------------------------------------------------------------------------------
//As a function of the file name, creates the file name for the thumbnail.
function file_name_to_thumbnail_name($in_filename)
{
   $extension_start = strrpos($in_filename, ".");
      //Find position of last "." in string.  This should precede the
      //file extension.
   if ($extension_start === FALSE)
   {
      //"." not found.  Should not happen.  Filenames were checked in advance.
      echo "Fatal internal error at line " . __LINE__ . "\n";
      exit(1);
   } 

   $filename_prefix    = substr($in_filename, 0, $extension_start);
   $filename_extension = substr($in_filename, $extension_start);

   $rv = $filename_prefix . CFG_THUMBNAIL_FILENAME_SUFFIX . $filename_extension;

   return $rv;
}
//--------------------------------------------------------------------------------
//Actually creates the thumbnail, and returns some information about what was
//done.
//
//The calls to the ImagMagick library take on the order of 5s per image if there
//is filtering.
function create_thumbnail(  $in_filename, 
                            $in_thumbnailname,
                          & $out_filename_filesize,
                          & $out_filename_xdim,
                          & $out_filename_ydim,
                          & $out_thumbnailname_filesize,
                          & $out_thumbnailname_xdim,
                          & $out_thumbnailname_ydim)
{
   //Assign output parameters just in case something doesn't get assigned.
   $out_filename_filesize      = 0;
   $out_filename_xdim          = 0;
   $out_filename_ydim          = 0;
   $out_thumbnailname_filesize = 0;
   $out_thumbnailname_xdim     = 0;
   $out_thumbnailname_ydim     = 0;

   //Establish target dimensions.  Two cases, depending on which is the longer
   //side.

   //Construct.
   $imagick = new Imagick();

   //Load image.
   $imagick->readImage($in_filename);

   //Get the dimensions of the image we just loaded.
   $geo               = $imagick->getImageGeometry(); 
   $out_filename_xdim = $geo['width']; 
   $out_filename_ydim = $geo['height']; 

   //Calculate target sizes.  We rearrange parameters based on which is our
   //longest side.
   if ($out_filename_xdim >= $out_filename_ydim)
   {
      //Longer width (x-dimension), or square.
      calc_thumbnail_conversion_pars
         (
         $out_filename_xdim,
         $out_filename_ydim,
         CFG_THUMBNAIL_DIMENSION_MAX,
         $out_thumbnailname_xdim,
         $out_thumbnailname_ydim,
         $orig_crop_dim_x,
         $orig_crop_dim_y,
         $orig_crop_start_x,
         $orig_crop_start_y
         );
   }
   else
   {
      //Longer height (y-dimension).
      calc_thumbnail_conversion_pars
         (
         $out_filename_ydim,
         $out_filename_xdim,
         CFG_THUMBNAIL_DIMENSION_MAX,
         $out_thumbnailname_ydim,
         $out_thumbnailname_xdim,
         $orig_crop_dim_y,
         $orig_crop_dim_x,
         $orig_crop_start_y,
         $orig_crop_start_x
         );
   }

   //For debugging only, might want to know intermediate calculation results.
   //echo "xcropdim, ycropdim, xcropstart, ycropstart: "
   //     .
   //     $orig_crop_dim_x
   //     .
   //     " "
   //     . 
   //     $orig_crop_dim_y
   //     .
   //     " "
   //     . 
   //     $orig_crop_start_x
   //     .
   //     " "
   //     . 
   //     $orig_crop_start_y
   //     .
   //     "\n";
           
   //Crop the original to try to preserve the aspect ratio of the thumbnail
   //as precisely as possible.
   $imagick->cropImage( 
                      $orig_crop_dim_x, 
                      $orig_crop_dim_y,
                      $orig_crop_start_x,
                      $orig_crop_start_y
                      );

   //For debugging only, might want to get a look at the cropped image, to
   //be sure nothing unexpected happens on the canvas.
   //$imagick->writeImage($in_filename . ".cropped.jpg");

   //Resize to thumbnail size.
   if (CFG_LANCZOS_FILTER_APPLY)
   {
      $imagick->resizeImage($out_thumbnailname_xdim, 
                            $out_thumbnailname_ydim, 
                            Imagick::FILTER_LANCZOS, 
                            1);
   }
   else
   {
      $imagick->resizeImage($out_thumbnailname_xdim, 
                            $out_thumbnailname_ydim, 
                            0, 
                            1);
   }

   //Create the border.
   $imagick->raiseImage(CFG_THUMBNAIL_BEVELED_BORDER_WIDTH, 
                        CFG_THUMBNAIL_BEVELED_BORDER_WIDTH, 
                        0, 
                        0, 
                        1);

   //Set compression to get a smaller thumbnail written, and strip
   //header information.  stripImage() seems to have the largest effect
   //on thumbnail file size, so leaving the thumbnail quality near 100%
   //is feasible.  The jump in file size between 90% and 95% seemed to be
   //fairly large (40% to 50%), so I left it at 90%.  My rationale is
   //that with the proliferation of mobile devices and cellular data,
   //getting the thumbnail as small as possible is more important than
   //the thumbnail looking perfect.  If the viewer wants a perfect image,
   //they can view the full-sized image.
   $imagick->setImageCompression(Imagick::COMPRESSION_JPEG); 
   $imagick->setImageCompressionQuality(90);
   $imagick->stripImage(); 

   //Write the thumbnail.
   $imagick->writeImage($in_thumbnailname);

   //Destroy to prevent memory leak.
   $imagick->clear(); 
   $imagick->destroy(); 

   //All of the writing is done.  Try to obtain the file sizes.
   $fsize = filesize($in_filename);
   if ($fsize !== FALSE)
      $out_filename_filesize = $fsize;
   $fsize = filesize($in_thumbnailname);
   if ($fsize !== FALSE)
      $out_thumbnailname_filesize = $fsize;
}
//--------------------------------------------------------------------------------
   //Write introductory message.
   hor_line_thick();
   echo CFG_PROGNAME . " Copyright (C) 2015 David T. Ashley\n";
   echo "This program comes with ABSOLUTELY NO WARRANTY; and is licensed under\n";
   echo "the GNU General Public License, Version 3.  A copy of this license is\n";
   echo "provided in the source code of this program.\n";
   hor_line_thin();
   //-----------------------------------------------------------------------------
   //Get and emit the names of everything in the directory.
   $file_list = get_file_names_in_dir();
   if ($file_list === FALSE)
   {
      echo "List of files from PHP function scandir() is empty.\n";
      echo "Serious internal error, or nothing to do.  Script cannot continue.\n";
      hor_line_thick();
      exit(1);
   }
   else
   {
     echo "Files in working directory (unsorted, unfiltered, " 
          . 
          count($file_list)
          . 
          " files):\n";
     for ($i = 0; $i < count($file_list); $i++)
        echo "   " . sprintf("[%5d]", $i) . " " . $file_list[$i] . "\n";
   }
   hor_line_thin();
   //-----------------------------------------------------------------------------
   //Remove the standard directory entries "." and ".." from the list, and 
   //remove any directories.
   $temp_list = $file_list;
   unset($file_list);
   $n = 0;
   for ($i = 0; $i < count($temp_list); $i++)
   {
      //echo "Checking " . $temp_list[$i] . "\n";

      if (strcmp($temp_list[$i], ".") == 0)
      {
         //. entry, not a file.
      }
      else if (strcmp($temp_list[$i], "..") == 0)
      {
         //.. entry, not a file.
      }
      else if (is_file($temp_list[$i]))
      {
         //This is a regular file.
         $file_list[] = $temp_list[$i];
         $n++;
      }
   }
   
   if ($n == 0)
      $file_list = FALSE;

   unset($n);
   unset($temp_list);
   //-----------------------------------------------------------------------------
   //If there is nothing to do, end the script.
   if ($file_list === FALSE)
   {
      echo "No files to process.\n";
      hor_line_thick();
      exit(0);
   }
   //-----------------------------------------------------------------------------
   //Sort the list.  This is a non-event.  The only rationale for sorting is that
   //it ensures that the same set of files will be processed in the same order,
   //regardless of the order provided by the underlying OS internals.
   sort($file_list);
   //-----------------------------------------------------------------------------
   //Emit the names we now have.
   echo "Files in working directory (directory entries removed, sorted, " 
        . 
        count($file_list)
        . 
        " files):\n";
   for ($i = 0; $i < count($file_list); $i++)
      echo "   " . sprintf("[%5d]", $i) . " " . $file_list[$i] . "\n";
   hor_line_thin();

   //-----------------------------------------------------------------------------
   //For each file that is appropriate and where the thumbnail does not already
   //exist, up to the maximum we may do in one invocation, create the thumbnail.
   $i         = 0;
   $completed = 0;
   while (($completed < CFG_MAX_THUMBNAILS_PER_INVOCATION) && ($i < count($file_list)))
   {
      if (is_full_sized_image_file_name($file_list[$i]))
      {
         $thumbnail_name = file_name_to_thumbnail_name($file_list[$i]);

         if (file_exists($thumbnail_name))
         {
            echo "   " . sprintf("[%5d]", $i) . " " . $file_list[$i] . " : skipping because corresponding thumbnail exists.\n";
            hor_line_thin();
         }
         else
         {
            echo "   " . sprintf("[%5d]", $i) . " " . $file_list[$i] . " : creating thumbnail.\n";

            echo "Creating thumbnail \"" .
                 $thumbnail_name .
                 "\" from image \"" .
                 $file_list[$i] .
                 "\".\n";

            create_thumbnail($file_list[$i], 
                             $thumbnail_name,
                             $filename_filesize,
                             $filename_xdim,
                             $filename_ydim,
                             $thumbnail_filesize,
                             $thumbnail_xdim,
                             $thumbnail_ydim);

            echo "Conversion complete.\n";
            echo "   Full-sized image file size/xdim/ydim = " .
                 $filename_filesize . "/" . $filename_xdim . "/" . $filename_ydim .
                 ",\n";
            echo "   Thumbnail image  filesize/xdim/ydim = " .
                 $thumbnail_filesize . "/" . $thumbnail_xdim . "/" . $thumbnail_ydim .
                 ",\n";

            hor_line_thin();
            $completed++;
         }
      }
      else
      {
         //Unsuitable base name.  Can't use it.
         echo "   " . sprintf("[%5d]", $i) . " " . $file_list[$i] . " : skipping due to unsuitable name.\n";
         hor_line_thin();
      }

      $i++;
   }

   //Emit a message about whether the program should be run again.  I am aware of
   //the uncovered case--where the last thumbnail was made on the last iteration
   //of this invocation--but I will leave it uncovered for now.  All that happens
   //is the user runs the program unnecessarily one more time.
   if ($completed == 0)
   {
      echo "No thumbnails were created--this program is done creating thumbnails.\n";
      echo "It is not necessary to run this program again.\n";
      hor_line_thin();
   }
   else
   {
      echo $completed . " thumbnail(s) were created.  Please run this program repeatedly again\n";
      echo "until no more thumbnails are created.\n";
      hor_line_thin();
   }

   echo CFG_PROGNAME . " execution ends.\n";
   hor_line_thick();
//--------------------------------------------------------------------------------
//End of File
//--------------------------------------------------------------------------------
?>