Merry Christmas, Racketeers!
Is there an easy way to draw text to a bitmap% with a gradient?
I briefly looked into adding linear-gradient% and
radial-gradient% support to slideshow/pict but unfortunately we
can't draw text using an arbitrary brush% as the draw-text method
of dc% ignores that.
My current trick is to draw the gradient to one bitmap, draw the
text to another bitmap, and then draw the first bitmap to a third
bitmap while copying the mask of the second. Is there a better
way?
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
#lang racket
(require slideshow/pict
racket/draw)
(define (compose-picts base alpha)
;; Return a bitmap% with the colors of base but the alpha of alpha.
(define-values (w h)
(values (inexact->exact (ceiling (pict-width base)))
(inexact->exact (ceiling (pict-height base)))))
(define-values (base-bitmap alpha-bitmap final-bitmap)
(values (make-bitmap w h)
(make-bitmap w h)
(make-bitmap w h)))
(define-values (base-dc alpha-dc final-dc)
(apply values (map (λ(bm) (new bitmap-dc% [bitmap bm]))
(list base-bitmap alpha-bitmap final-bitmap))))
(send base-dc set-smoothing 'aligned)
(draw-pict base base-dc 0 0)
(send alpha-dc set-smoothing 'aligned)
(draw-pict alpha alpha-dc 0 0)
(send final-dc draw-bitmap base-bitmap 0 0 'solid #f alpha-bitmap)
final-bitmap)
;; The text to render
(define my-text
(scale (text "Hello World") 4))
;; The linear-gradient% to render
(define gradient
(new linear-gradient% [x0 0] [y0 0] [x1 0] [y1 (pict-height my-text)]
[stops (list (list 0.0 (make-object color% 0 0 0))
(list 1.0 (make-object color% 255 0 0)))]))
;; A box containing the gradient
(define gradient-box
(dc
(λ(dc w h)
(send dc set-pen (make-object pen% "white" 1 'transparent))
(send dc set-brush (new brush% [gradient gradient]))
(send dc draw-rectangle
0 0 (pict-width my-text) (pict-height my-text)))
(pict-width my-text) (pict-height my-text)))
;; The final result: Gradient-filled text!
(bitmap (compose-picts gradient-box my-text))
--
Heave ho,
_mike
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