PPM.md

structure PPM

Support for the simple .ppm image file format.

type pixel = Color.pixel

Colors are defined by the Color module.

type image = {height: int, width: int, data: pixel Seq.t}

An image is a Seq.t where the pixel at (i,j) is stored at index i*width + j. That is, i (where 0 <= i < height) is the row index, and j (where 0 <= j < width) is the column index. The top-left of the image is at (0,0).

Note: this representation is identical to GIF.image, making it easy to interface between the two structures.

val elem: image -> (int * int) -> pixel

Look up the pixel at indices (i,j).

val read: string -> image

Open a .ppm file at the given path and parse an image from it. Currently supports P3 and P6 formats.

val write: string -> image -> unit

write path img outputs the image img to a file at the path path (which should have .ppm file extension). The output file is in P6 format.

Subimages

type box = {topleft: int * int, botright: int * int}

A box-shaped region within an image is defined by its top-left and bottom-right coordinates. For a box {topleft=(i1,j1), botright=(i2,j2)}, the height of the box is i2-i1 and the width is j2-j1.

val subimage: box -> image -> image

Extract a box-shaped region of an image.

val replace: box -> image -> image -> image

replace box image subimage replaces the region box of image with subimage, returning a new image. The dimensions of subimage must be at least as big as box.