package bimage-gtk

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Bimage_gtk allows images to be displayed in GTK windows


Dune Dependency





bimage — Image processing library


bimage is an image processing library for OCaml.


  • Simple image type based on bigarrays

  • Supports u8, u16, i32, i64, f32, f64, complex32 and complex64 datatypes

  • Multiple layout support (Planar/Interleaved)

  • Composable image operations

  • Image I/O using ImageMagick/GraphicsMagick and stb_image in (bimage-unix)

  • Support for displaying images using GTK (bimage-gtk) or SDL (bimage-sdl)

bimage is distributed under the ISC license.



bimage can be installed with opam:

opam install bimage

Additionally, bimage-unix, which provides ImageMagick and FFmpeg bindings, can be installed by running:

opam install bimage-unix

If you don't use opam consult the opam file for build instructions.


An example showing how to create an image and how to use Image.for_each:

open Bimage

let _ =
(* Create a new image *)
let a = Image.create u8 gray 64 64 in

(* Iterate over each pixel *)
let _ =
    Image.for_each (fun x y _px ->
      Image.set a x y 0 (x + y)
    ) a

(* Save the image using ImageMagick *)
Bimage_unix.Magick.write "test1.jpg" a

The above example does direct image processing, however you may also use Exprs which can be used to compose operations.

Turning an Expr.t into an Op.t:

open Bimage
open Expr

(** Create an expression to get the average pixel for each pixel,
    [~@] is used to create [index] parameters *)
let avg = func (pixel ~@0 X Y) (fun _x _y _c px ->
  Pixel.fold ( + ) 0 px

let avg_minus_1 = Expr.(avg -. 1.0)
let avg_times_3 = Expr.(avg *. 3.0)

(** Turn it into an Op, which can be evaulated with `Op.eval` *)
let op = Expr.op avg

(** Exprs can also be evaluated directly using `Op.eval_expr` *)
let result = Op.eval_expr avg ~output:dest [| a |]

An example composing two Ops:

open Bimage
open Bimage_unix

let _ =
(* Load an image using ImageMagick *)
let a = match f32 rgb "test/test.jpg" with
  | Ok img -> img
  | Error e -> failwith (Error.to_string e)

(* Create an operation to convert to grayscale and subtract 1.0 *)
let f = Op.(grayscale &- scalar 0.5) in

(* Create a destination image *)
let dest = Image.like_with_color gray a in

(* Run the operation *)
let () = Op.eval f ~output:dest [| a |] in

(* Save the image using ImageMagick *)
Magick.write "test2.jpg" dest


The documentation and API reference is generated from the source interfaces. It can be consulted online or via odig doc bimage.


In the distribution sample programs and tests are located in the test directory. They can be built and run with:

dune runtest

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