Erlang Graphical Drawer (fhunleth fork)

Erlang Graphical Drawer (egd) is an interface for 2d-image rendering and is used by Percept to generate dynamic graphs to its web pages. All code is pure Erlang, no drivers needed.

The library is intended for small to medium image sizes with low complexity for optimal performance. The library handles horizontal lines better then vertical lines.

The foremost purpose for this module is to enable users to generate images from Erlang code and/or datasets and to send these images to either files or web servers.

This EGD fork has the following updates:

• egd:text/5 supports both Erlang and Elixir strings (binaries) with Unicode
• Rendering unknown glyphs doesn't crash
• The bdf2wingsfont tool for converting BDF fonts is included in the repository
• Various corrections to named color values (white, red and a few others)
• Add Cozette font for more complete Unicode glyph support
• Add Terminus font and add more glyphs to default 6x11 font

Installation

This is a drop in replacement for egd and uses the same namespace. It's published under the hex egd_fhunleth package, though.

If using rebar3, add:

{egd, "0.11.0", {pkg, egd_fhunleth}}

If using mix, add:

{:egd, "~> 0.11.0", hex: :egd_fhunleth}

File example

Drawing examples:

-module(img).

-export([do/0]).

do() ->
    Im = egd:create(200,200),
    Red = egd:color({255,0,0}),
    Green = egd:color({0,255,0}),
    Blue = egd:color({0,0,255}),
    Black = egd:color({0,0,0}),
    Yellow = egd:color({255,255,0}),

    % Line and fillRectangle

    egd:filledRectangle(Im, {20,20}, {180,180}, Red),
    egd:line(Im, {0,0}, {200,200}, Black),

    egd:save(egd:render(Im, png), "test1.png"),

    egd:filledEllipse(Im, {45, 60}, {55, 70}, Yellow),
    egd:filledEllipse(Im, {145, 60}, {155, 70}, Blue),

    egd:save(egd:render(Im, png), "test2.png"),

    R = 80,
    X0 = 99,
    Y0 = 99,

    Pts = [ {X0 + trunc(R*math:cos(A*math:pi()*2/360)),
             Y0 + trunc(R*math:sin(A*math:pi()*2/360))
            } || A <- lists:seq(0,359,5)],
    lists:map(
        fun({X,Y}) ->
            egd:rectangle(Im, {X-5, Y-5}, {X+5,Y+5}, Green)
        end, Pts),

    egd:save(egd:render(Im, png), "test3.png"),

    % Text
    Filename = filename:join([code:priv_dir(egd), "fonts", "6x11_latin1.wingsfont"]),
    Font = egd_font:load(Filename),
    {W,H} = egd_font:size(Font),
    String = "egd says hello",
    Length = length(String),

    egd:text(Im, {round(100 - W*Length/2), 200 - H - 5}, Font, String, Black),

    egd:save(egd:render(Im, png), "test4.png"),

    egd:destroy(Im).

First save:

Second save:

Third save:

Fourth save:

ESI example

Using egd with inets ESI to generate images on the fly:

-module(img_esi).

-export([image/3]).

image(SessionID, _Env, _Input) ->
    mod_esi:deliver(SessionID, header()),
    Binary = my_image(),
    mod_esi:deliver(SessionID, binary_to_list(Binary)).

my_image() ->
    Im = egd:create(300,20),
    Black = egd:color({0,0,0}),
    Red = egd:color({255,0,0}),
    egd:filledRectangle(Im, {30,14}, {270,19}, Red),
    egd:rectangle(Im, {30,14}, {270,19}, Black),

    Filename = filename:join([code:priv_dir(egd), "fonts", "6x11_latin1.wingsfont"]),
    Font = egd_font:load(Filename),
    egd:text(Im, {30, 0}, Font, "egd with esi callback", Black),
    Bin = egd:render(Im, png),
    egd:destroy(Im),
    Bin.

header() ->
    "Content-Type: image/png\r\n\r\n".

Result:

For more information regarding ESI, please see inets application mod_esi.