I have some code that writes individual images to pdfs (see below).
If there's a lot of "texture" in the images, these files can be very large
indeed.
I assume that by default the image is encoded as a kind of embedded png.
I would like to be able to change the compression -- e.g. specify jpeg.
My currently workaround is to save from Racket as a png, and then convert
externally via ImageMagick: first to jpeg, then to pdf.
(How) can I achieve the same result directly from Racket?
Many thanks
Dan
----
#lang racket
(require racket/draw
(only-in 2htdp/image
save-image
image-width
image-height
scale))
(define (image->bitmap image)
(let* ([width (image-width image)]
[height (image-height image)]
[bm (make-bitmap width height)]
[dc (send bm make-dc)])
(send dc clear)
(send image draw dc 0 0 0 0 width height 0 0 #f)
bm))
(define (image->pdf image output-file [mag 1.0])
(define dc
(new pdf-dc%
[ interactive #f ]
[ use-paper-bbox #f ]
[ width (* 0.8 mag (image-width image))] ; Default scale is 0.8
0.8
[ height (* 0.8 mag (image-height image))]
[ output output-file ]))
(send* dc
(scale mag mag)
(start-doc "useless string")
(start-page))
(send dc draw-bitmap (image->bitmap image) 0 0)
(send* dc
(end-page)
(end-doc)))
(module+ test
(require (only-in 2htdp/image
circle text square overlay above))
(define im
(overlay
(above
(circle 50 'solid 'red)
(text "This is a red circle" 12 'black))
(square 150 'solid 'lightblue)))
(image->pdf im "image-test.pdf")
(save-image im "image-test.png"))
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