Pngex

A library for generating PNG images.

Installation

If available in Hex, the package can be installed by adding pngex to your list of dependencies in mix.exs:

def deps do
  [
    {:pngex, "~> 0.1.0"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/pngex.

Generates images

Pixel data

Use binary, list of integers or list of tuples to express pixel data of the image.

Binary

typeexample
:rgb<<r0, g0, b0, r1, g1, b1, ...>>
:rgba<<r0, g0, b0, a0, r1, g1, b1, a1, ...>>
:gray<<c0, c1, ...>
:gray_and_alpha<<c0, a0, c1, a1, ...>>
:indexed<<c0, c1, ...>

List of integers

typeexample
:rgb[r0, g0, b0, r1, g1, b1, ...]
:rgba[r0, g0, b0, a0, r1, g1, b1, a1, ...]
:gray[c0, c1, ...]
:gray_and_alpha[c0, a0, c1, a1, ...]
:indexed[c0, c1, ...]

List of tuples

typeexample
:rgb[{r0, g0, b0}, {r1, g1, b1}, ...]
:rgba[{r0, g0, b0, a0}, {r1, g1, b1, a1}, ...]

Examples

RGB

Prepare bitmap image data
bitmap =
  for n <- 0..65535 do
    r = div(n, 256)
    g = rem(n, 256)
    b = 255 - max(r, g)
    {r, g, b}
  end
Generate PNG image
pngex =
  Pngex.new()
  |> Pngex.set_type(:rgb)
  |> Pngex.set_depth(:depth8)
  |> Pngex.set_size(256, 256)

image = Pngex.generate(pngex, bitmap)

File.write("rgb8_256x256.png", image)

or

image =
  Pngex.new(
    type: :rgb,
    depth: :depth8,
    width: 256,
    height: 256
  )
  |> Pngex.generate(bitmap)

File.write("rgb8_256x256.png", image)

Indexed (Palette)

Prepare palette colors
palette = for n <- 0..255, do: {n, 255, 255 - n}
Prepare bitmap image data
bitmap = for n <- 0..65535, do: rem(n, 256)
Generate PNG image
image =
  Pngex.new(
    type: :indexed,
    depth: :depth8,
    width: 256,
    height: 256,
    palette: palette
  )
  |> Pngex.generate(bitmap)

File.write("indexed8_256x256.png", image)

Grayscale

Prepare bitmap image data
bitmap = for n <- 0..65535, do: rem(n, 256)
Generate PNG image
image =
  Pngex.new(
    type: :gray,
    depth: :depth8,
    width: 256,
    height: 256
  )
  |> Pngex.generate(bitmap)

File.write("gray8_256x256.png", image)

Avaiable formats

type \ depth:depth1:depth2:depth4:depth8:depth16
:indexedvvvv
:grayscalevvvvv
:grayscale_and_alphavv
:rgbvv
:rgbavv