R7RS-PNM

R7RS-PNM is a R7RS library for handling PNM (Portable Any Map) files, providing functionality for reading and writing PNM files,as well as accessing and modifying pixel data.

Usage

Import `(image-format pnm)` library

(import (image-format pnm))

Image

`(pnm-image? x) → boolean`

Returns #t if x is a valid pnm-image object; otherwise, it returns #f.

`(pnm-image-type pnm-image) → 'pbm | 'pgm | 'ppm`

Returns the type of the given pnm-image.

pbm: Portable Bit Map
pgm: Portable Gray Map
ppm: Portable Pixel Map

`(pnm-image-width pnm-image) → integer`

Returns the width of pnm-image.

`(pnm-image-height pnm-image) → integer`

Returns the height of pnm-image.

PBM (Portable Bit Map)

`(make-pbm-image width height) → <pnm-image>`

Returns a new Portable Bit Map (PBM) image with the specified width and height.

`(pnm-image-maxval pbm-image) → #t`

Returns the maximum value for pixel intensity in a PBM image, which is

always #t for PBM images, indicating binary values (black and white).

`(pnm-image-ref pbm-image x y) → boolean`

Returns the value of the pixel at coordinates (x, y) in the specified image. The return value is #t for a white pixel and #f for a black pixel.

`(pnm-image-set! pbm-image x y b)`

Sets the pixel at coordinates (x, y) in the specified pnm-image to the boolean value b. If b is #t, the pixel is set to white; if #f, it is set to black.

PGM (Portable PGM Map)

`(make-pgm-image width height [maxval]) → <pnm-image>`

Creates a new Portable Gray Map (PGM) image with the specified width and height. The optional maxval parameter defines the maximum pixel intensity, defaulting to 255 if not provided.

`(pnm-image-maxval pgm-image) → integer`

Returns the maximum pixel intensity value for the specified PGM image.

`(pnm-image-ref pgm-image x y) → integer`

Returns the gray value of the pixel at coordinates (x, y) in the specified PGM image. The value is an integer between 0 and maxval.

`(pnm-image-set! pgm-image x y v)`

Sets the pixel at coordinates (x, y) in the specified PGM image to the given integer value v, which must be between 0 and maxval.

PPM (Portable PPM Map)

`(make-ppm-image width height [maxval]) → <pnm-image>`

Creates a new Portable Pixel Map (PPM) image with the specified width and height. The optional maxval parameter defines the maximum color intensity, defaulting to 255 if not provided.

`(pnm-image-maxval ppm-image) → integer`

Returns the maximum color intensity value for the specified PPM image.

`(pnm-image-ref ppm-image x y) → (values integer integer integer)`

Returns the RGB values of the pixel at coordinates (x, y) in the specified PPM image as three integers, representing the red, green, and blue components, respectively.

`(pnm-image-set! ppm-image x y r g b)`

Sets the pixel at coordinates (x, y) in the specified PPM image to the given RGB values r, g, and b, which must be integers between 0 and maxval.

Reading

`(pnm-image-read port) → <pnm-image>`

Reads a PNM image from the specified input port and returns the corresponding image object (PBM, PGM, or PPM).

`(pnm-parse-error? exn) → boolean`

Returns #t if the exception exn is a parse error that occurred during the execution of the pnm-image-read procedure; otherwise, it returns #f.

Writing

`(pnm-image-write pnm-image port)`

Writes the specified pnm-image (PBM, PGM, or PPM) to the given output port.

Downloading Code with Git

git clone https://git.tojo.tokyo/r7rs-pnm.git

License

This library is released under the LGPLv3+ License. See the COPYING and COPYING.LESSER files for more details.