77 lines
2.6 KiB
Racket
77 lines
2.6 KiB
Racket
#lang scribble/doc
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@(require "common.rkt" scribble/eval (for-label slideshow/pict))
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@(define class-eval (make-base-eval))
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@(interaction-eval #:eval class-eval (require racket/class racket/draw slideshow/pict))
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@defclass/title[radial-gradient% object% ()]{
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A @deftech{radial gradient} is used with a @racket[brush%] to fill
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areas, such as the interior of a rectangle or ellipse, with smooth
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color transitions.
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Colors transitions are based on two circles and the sequence of circles that
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``morph'' from the starting circle to the ending circle. Colors are
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assigned to stop circles in the sequence, and the colors of
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the start and end circles radiate inward and outward to points that
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are not on any intermediate circles.
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@defconstructor[([x0 real?]
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[y0 real?]
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[r0 real?]
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[x1 real?]
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[y1 real?]
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[r1 real?]
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[stops (listof (list/c (real-in 0 1) (is-a?/c color%)))])]{
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Creates a radial gradient with the starting circle as the one with
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radius @racket[r0] centered at (@racket[x0], @racket[y0]) and the
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ending circle as the one with radius @racket[r1] centered at
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(@racket[x1], @racket[y1]). The @racket[stops] list assigns colors to
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circles, where @racket[0.0] corresponds to the starting circle,
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@racket[1.0] corresponds to the ending circle, and numbers in between
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correspond to circles in between.
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@examples[
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#:eval class-eval
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(define no-pen (make-object pen% "BLACK" 1 'transparent))
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(define brush-grad (new brush% [gradient (new radial-gradient%
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[x0 400] [y0 150] [r0 10] [x1 400] [y1 150] [r1 100]
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[stops
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(list (list 0 (make-object color% 255 0 0))
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(list 0.5 (make-object color% 0 255 0))
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(list 1 (make-object color% 0 0 255)))])]))
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(define brush-grad2 (new brush% [gradient
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(make-object radial-gradient% 150 150 0 150 150 100
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(list (list 0 (make-object color% 0 0 255))
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(list 0.5 (make-object color% 0 255 0))
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(list 1 (make-object color% 255 0 0))))]))
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(dc (lambda (dc x y)
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(send dc set-pen no-pen)
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(send dc set-brush brush-grad2)
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(send dc draw-ellipse 50 50 200 200)
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(send dc set-brush brush-grad)
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(send dc draw-rectangle 300 50 200 200)) 550 300)
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]}
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@defmethod[(get-circles)
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(values real? real? real? real? real? real?)]{
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Returns the gradient's boundary circles as @racket[_x0], @racket[_y0],
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@racket[_r0], @racket[_x1], @racket[_y1], and @racket[_r1].
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}
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@defmethod[(get-stops)
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(listof (list/c (real-in 0 1) (is-a?/c color%)))]{
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Returns the gradient's list of color stops.
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}}
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@(close-eval class-eval)
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