image-transformer

A simple modular application for transforming images in 24-bit BMP format.

This repository was created for an article by the following link: https://habr.com/ru/post/529262/.

Requirements

To build this app you need to have following tools:

• GNU gcc
• GNU Flex
• GNU Bison
• GNU make

Build & run

To build it you need to run make in the root directory. As result you will have an executable file image-transformer.

To get help just run ./image-transformer -h.

Summary:

make # build
./image-transformer -h # run
./test.it test.bmp # run test script via executable

Scripting language

An example script is located at ./test.it.

Scripts consist of comments started from # and transformations:

# comment

transformation();
module.transformation_from_module();

transformation_with_args(
    1,      # integer value
    2.0,    # floating point value
    "3",    # string value
    four    # identifier (from module) value
);

Transformation with specified module will be loaded from shared objects. Shared objects should have name in format <module_prefix><module>.so or <module_prefix><module>, where module prefix is defined via program arguments.

If module is not specified transformation will be loaded from "standard library". There are some standard utilitary "transformations":

print_ansi([pixel])

Print image on terminal with ANSI ESC-sequences.

pixel is an optional parameter, that specifies string that will be used to print each pixel of image, default " " (two spaces).

echo([message])

Print message with newline. If message is not specified, prints only newline.

die([message])

Abort script with message. If message is not specified, error message will be "suicide".

Module writing

Modules are simple ELF shared objects with exported functions.

Transformation functions should have following signature:

/* Header files from application source code */
#include <value.h>
#include <image.h>

const char * transformation_name(struct image * image, uint32_t argc, const struct value * argv) {
    /* transformation code */
}

To call transformation described above you need to write a code like the following one in script and make sure that shared library can be found by an application:

# Assume that "transformation_name" is compiled in "module_name.so" shared object
module_name.transformation_name();