Requirements:
- PHP supporting
version GD 1.6.3
or better (may or may not work lower than that, tested with gd-1.8.3).
Effort was made to avoid php functions requiring GD 2.x or later however
that may impact using more colors and possibly type 2 true type
fonts. Let us know your
experiences.
- True Type Font rendering for GD
program, tested with freetype-1.3.1
- And probably several other applications that were not obvious to you,
let us know what was not obvious and we will list here :)
Demonstration: http://www.cocoavillagepublishing.com/development/tools/php/scripts/blockautosubmit/
License was intended to be BSD style so that it can be
used and modified by others for commercial and non-commercial use:
http://www.cocoavillagepublishing.com/development/tools/php/scripts/blockautosubmit/license.txt
Archived source using ZIP:
http://www.cocoavillagepublishing.com/development/tools/php/scripts/download/blockautosubmit_v0.2.zip
older:
blockautosubmit_v0.1.zip
Archived source using TAR compressed with GZIP:
http://www.cocoavillagepublishing.com/development/tools/php/scripts/download/blockautosubmit_v0.2.tar.gz
older:
blockautosubmit_v0.1.tar.gz
FAQ
Q. The image appears but the characters are not showing
up, suggestions?
A. If for some reason the session is not
registering the random character string created on the form page then when
the web server tries to open the graphic "generateimage.php" that
php script won't be able to get the string from the session so you may want
to verify that the scripts are able to use the session properly to store the
important random string for the image.
Test that your setup with php can create
images with text using the functions like is_dir and imagegettftext that are
used in by file generateimage.php
You may need to edit php.ini and elsewhere to allow script to read the
subdirectory ttf or modify/simplify the code so it does not have to get a
directory listing to determine what ttf fonts it can choose. Also note that
we set the output of generateimage.php to be jpeg but you may could use png.
Note that the imagegettftext
function allows us to rotate the text!
Q. How about ASCII art instead of an image?
A. Added that option
with version 0.2 and play with settings in the config.php file
Q. Can I make it harder to OCR by changing the background?
A. Look at generateimage.php and you will see a
conditional that if $BASaddimgnoise = "yes" then the script will create
random arcs over the background in the font color and an off color. To
engage, edit config.php and change the variable $BASaddimgnoise to be "yes".
We think that something better could be done and welcome contributions, but
if possible we request that the noise method work with versions of GD prior
to 2.x so that limits some of the php image commands that may be more
convenient for drawing. For example, the function imagefilledellipse
was added in PHP 4.0.6 and requires GD 2.0.1 or later
Q. The characters are to hard to read, and I
sometimes can't tell difference between number one and some letters, what can
I do?
A. You could modify the script to use
numbers only on the random generation. Also you could reduce the ttf fonts
to choose from, and or replace with ttf files that have easier to read
fonts. Many sites using image verification are only using numbers that
don't randomly rotate the characters but instead have an image with static
dots, lines and curves. In our example we went to the extreme
selecting what we thought to be hard to OCR fonts that the license was
interpreted as freely distributable for commercial use.
Q. Why did you use the verbose <script language="php">
tags instead of <?
A. We recommend you don't be lazy on the
tags if the files may be edited in by other applications. Programs
like Dreamweaver and Frontpage know how to handle <script
language="xyz">blah </script>, however they can not display in a
design or preview view with the abbreviated tagging of PHP.
Q. Why gd?
A. GD is available on most php installations.
We think other applications like NetPBM and ImageMagick which are used by
Gallery which is
php may give more resources and writers may want to consider that.
Q. Why did you write such sloppy code,
why not all functions and classes?
A. It was a hack with spare time not elegance, but
with lots of comments. Step forward and rewrite it and donate it back or
under the BSD license take the code and redo or rather fork the works. Let
us know and we will link.
Q. Why
not use another figlet class that is more recently supported like the class
in PEAR?
A. The included php figlet class is
about two years old and the author does not support it on the mentioned
website, but it seems to be working. Some php sites are not setup
with PEAR, so we used this simpler file. Note the license for the
php filget class not by us and if in the future someone complains we
will have to reference it or remove it. Perhaps in the future we
will go with PEAR or other figlet if need be. See
http://www.figlet.org/
for more information about figlet.
Q. How about an audio captcha?
Here is an article of someone using an audio captcha:
http://www.ejeliot.com/pages/2
