How to read a bitmap in OCAML?

Question

I want to read a bitmap file (from the file system) using OCAML and store the pixels (the colors) inside an array which have th dimension of the bitmap, each pixel will take

Answer 1

CAMLIMAGE should do it. There is also a debian package (libcamlimage-ocmal-dev), as well as an installation through godi, if you use that to manage your ocaml packages.

As a useful example of reading and manipulating images in ocaml, I suggest looking over the code for a seam removal algorithm over at eigenclass.

You can also, as stated by jonathan --but not well-- call C functions from ocaml, such as ImageMagick. Although you're going to do a lot of manipulation of the image data to bring the image into ocaml, you can always write c for all your functions to manipulate the image as an abstract data type --this seems to be completely opposite of what you want though, writing most of the program in C not ocaml.

Since I recently wanted to play around with camlimages (and had some trouble installing it --I had to modify two of the ml files from compilation errors, very simple ones though). Here is a quick program, black_and_white.ml, and how to compile it. This should get someone painlessly started with the package (especially, dynamic image generation):

   let () =
       let width  = int_of_string Sys.argv.(1)
       and length = int_of_string Sys.argv.(2)
       and name   = Sys.argv.(3)
       and black = {Color.Rgb.r = 0; g=0; b=0; }
       and white = {Color.Rgb.r = 255; g=255; b=255; } in
       let image = Rgb24.make width length black in
       for i = 0 to width-1 do
           for j = 0 to (length/2) - 1 do
               Rgb24.set image i j white;
           done;
       done;
       Png.save name [] (Images.Rgb24 image)

And to compile,

ocamlopt.opt -I /usr/local/lib/ocaml/camlimages/ ci_core.cmxa graphics.cmxa ci_graphics.cmxa ci_png.cmxa black_and_white.ml -o black_and_white

And to run,

./black_and_white 20 20 test1.png