Lucy McClane ebdb3bbc12 test rotate_glyph fix | 2 年 前 | |
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examples | 2 年 前 | |
patterns | 3 年 前 | |
src | 2 年 前 | |
test | 2 年 前 | |
ttf | 3 年 前 | |
.gitignore | 3 年 前 | |
LICENSE | 3 年 前 | |
Makefile.am | 3 年 前 | |
README.md | 2 年 前 | |
bootstrap | 3 年 前 | |
configure.ac | 2 年 前 | |
make-singleh.sh | 2 年 前 |
Highly customizable
captcha
making library.
The screenshot was made using example7.c
The main idea was to make a general purpose graphic library with no dependencies
in C
to draw some primitives with text in a web application. And then I've noticed
that I don't have a good captcha
to prevent robots to post their shit, so, now
here it is.
C
single-header
library (thanks to @acetone)To create a single-header
library just use:
./make-singleh.sh
If command succeed, you'll have the libcaptcha.h
file that you can use as
a single header library.
It is as simple as
./bootstrap
./configure
make
make install
I thought to name this section "limitations", because libcaptcha
doesn't
provide functionality to align fonts, work with alpha channels and so on. But
captcha
does not need those "features". Rather vice versa - it requires to be ugly
and random.
The general idea is to provide a simplified API
(I call it level zero or preset0)
and more advanced primitives.
The simplified functionality consists of 3 simple steps:
The advanced functions are quite low level stuff, that requires some understaindig of every step. I've provided some examples which indended to help you with understanding those "low level" functions. By you I mean me in the future :)
First of all we need some text, and this text should be placed using
some random values. Don't warry, preset
functions make all those
random stuff by itself.
Here is example how to use lc_preset_text()
:
lc_bmp * text = lc_preset_text( // returns single channel lc_bmp*
"path_to_font.ttf", // path to font file
"HELLOWORLD", // our text
38, // minimum font size
50, // maximum font size (if zero, all glyphs will be 38)
1, // 1 - rotate characters, 0 - off
10, // horizontal random offset
10); // vertical random offset
There's some simply functions that make noise
and square
captchas.
lc_bmp * bmp = lc_preset_square(
text, // is our font object with text
1, // spacing
2); // square size (2 is very small)
For circles:
lc_bmp * bmp = lc_preset_circle(
text, // is our font object with text
0, // spacing
14); // circle radius (it is not a real radius, but close to it)
Lets save our image into a png
file:
lc_save_png("helloworld.png", bmp);
Don't forget to free()
memory:
lc_free(bmp);
lc_free(text);
Also you can make some noisy pattern instead of squares, its usage is simple:
lc_bmp * noise = lc_preset_noise(text);
That's it.
Check out examples
Get familiar with general concept. example1.c
How to make a random sized glyphs. example2.c
Apply random positions for glyphs. example3.c
Get familiar with patterns made from png images. example4.c
Patterns, patterns everywhere. example5.c
Some crazy stuff. example6.c
Don't forget to use lc_free()
to free all the stuff libcaptcha
returns to
you.
I've noticed that it is very easy to get lost sometimes, just use valgrind
.
GPLv2
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 2
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.
Author: g0tsu
Email: g0tsu at dnmx.0rg