#lang scribble/manual

@(require planet/scribble
          scribble/eval
          planet/version          
          "main.rkt")

@(define my-eval (make-base-eval))

@(my-eval `(require (planet ,(this-package-version-symbol main))
                    2htdp/image))

@(require (for-label racket
                     2htdp/image
                     "main.rkt"))

@title{Color Utilities}

@(defmodule/this-package main)


These are some convenience tools to transform images
in the 2htdp/image library.  The convenience consists of producing new colors by
changing a single intensity by name, and a for-like comprehension for images.

@defproc[(<-component [band symbol?] [old color?])
         (color)]{Produces @racket[band] portion of @racket[old]'s @racket[color].}         
                 
@defproc[(+color [component symbol?] [val number?] [col color?])
         (color)]{Produces @racket[color] based on @racket[old], but
                 using intensity @racket[val] in band corresponding
                 to @racket[component].}
                 
@defproc[(green+color [val number?] [col color?])
         (color)]{Produces @racket[color] based on @racket[col], but
                  with the green intensity to @racket[val].
                  
                  @examples[#:eval my-eval
                            (green+color 10 (color 1 2 3 4))]}

@defform[(for/image ([id image-expr] ...)
           body ...+)]{Produce new @racket[image] by binding @racket[id]
                       to each element of @racket[image-expr]'s @racket[color-list]
                       in turn.}