<div dir="ltr">I'm not sure I can give you more than just hints (and certainly not a specification) but probably the difference is that pict->bitmap is drawing the pict at (0,0) in the DC and scribble is drawing it at some random place. But yeah, I'm sorry, that's still just a guess.<div> </div><div>And the examples at that link are really fantastic!</div><div> </div><div><div>Robby</div><div> </div></div></div><div class="gmail_extra"> <div class="gmail_quote">On Tue, Feb 11, 2014 at 1:03 PM, Jens Axel Søgaard <<a href="mailto:jensaxel@soegaard.net" target="_blank">jensaxel@soegaard.net</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">2014-02-11 19:39 GMT+01:00 Robby Findler <<a href="mailto:robby@eecs.northwestern.edu">robby@eecs.northwestern.edu</a>>: <div class="">> Is the problem that you need to use (more) absolute coordinates in the > coordinate arguments to linear-gradient% (either that or set the origin of > the dc, in the case that you wanted to create the brush only once)? </div>The problem is that it is unspecified (as far as I know) whether brushes used in picts are specified using absolute or relative coordinates. For solid brushes this makes no difference. For non-solid brushes (gradients and textures) there is a choice to be made. I got surprised by the behavior and thought of it as a bug (I was looking for one - I have an example where a pict shows up perfectly in DrRacket but renders differently in Scribble). If I in shady make a new gradient each time the pict is to be drawn, I get the behavior I want: (new linear-gradient% [x0 x] [y0 y] [x1 (+ x (* 2 r))] [y1 y] ; horizontal gradient <div class=""> [stops (list (list 0 red) ; (0,0) to ( r,0) red->green (list 1/2 green) ; (r,0) to (2r,0) green->blue (list 1 blue))]) </div>Since the pict constructors such as filled-rectangle use the pen, there were no way to figure out what was intended. The last example here: shows that Scribble converts p and (pict->bitmap p) differently. I am still puzzled by this. <a href="http://soegaard.github.io/docs/metapict/metapict.html#%28part._example-rgb-triangle%29" target="_blank">http://soegaard.github.io/docs/metapict/metapict.html#%28part._example-rgb-triangle%29</a> /Jens Axel <div class="HOEnZb"><div class="h5"> > On Tue, Feb 11, 2014 at 10:49 AM, Jens Axel Søgaard <<a href="mailto:jensaxel@soegaard.net">jensaxel@soegaard.net</a>> > wrote: >> >> The intent of hc-append is that (hc-append p1 p2) draws p1 and p2 >> beside each other. >> >> The question is whether (hc-append p p) should draw to identical picts? >> >> When I use a non-solid brush I get the two ps are drawn differently. >> In (hc-append p1 p2) I was expecting a transformation (translation) on >> the brush. >> >> As a demonstration I offer the following program (a bit long, but >> hopefully clear. >> >> See a syntax-highligthed version here: <a href="http://pasterack.org/pastes/7953" target="_blank">http://pasterack.org/pastes/7953</a> >> The DrRacket output is here: <a href="http://imgur.com/5BRiY0Z" target="_blank">http://imgur.com/5BRiY0Z</a> >> >> /Jens Axel >> >> >> #lang racket >> (require pict) >> >> ; debug : value pict -> pict >> ; return a pict, that when drawn prints the >> ; brush and drawing context transformation >> (define (debug who pict) >> (dc (lambda (dc x y) >> (define b (send dc get-brush)) >> (define bt (send b get-transformation)) >> (define dct (send dc get-transformation)) >> (displayln (list who 'x x 'y y 'brush: bt 'dc: dct)) >> (draw-pict pict dc x y)) >> (pict-width pict) (pict-height pict))) >> >> (define r 20) ; use same box side for the entire example >> >> ; a black filled rectangle >> (define (rect) (filled-rectangle r r)) >> >> ;;; Examine whether hc-append does any transformation. >> "Expected Image: Two squares a black and a red" >> "Expected Transformation: Same for A and B. Some difference for C." >> (debug 'A >> (hc-append (debug 'B (rect)) >> (debug 'C (colorize (rect) "red" )))) >> >> ;;; -------------------------------------------------------------- >> (require racket/draw) >> >> ; colors >> (define (color: name) (send the-color-database find-color name)) >> (define red (color: "red")) >> (define green (color: "green")) >> (define blue (color: "blue")) >> >> ; square-path : real real real real -> path% >> ; make square with side r and upper left corner (x,y) >> (define (square-path x y w h) >> (define p (new dc-path%)) >> (send p move-to x y) >> (send p line-to x (+ y h)) >> (send p line-to (+ x w)(+ y h)) >> (send p line-to (+ x w)(+ y 0)) >> (send p line-to (+ x 0)(+ y 0)) >> p) >> >> ; fill : pict -> pict >> ; draw a path around pict using current pen and brush >> (define (fill pict) >> (define w (pict-width pict)) >> (define h (pict-height pict)) >> (dc (lambda (dc x y) >> (draw-pict pict dc x y) >> (send dc draw-path (square-path x y w h))) >> w h)) >> >> ; shady : pict -> pict >> ; Draws pict with a brush given by a linear, horizontal >> ; gradient from (0,0) to (0,2r). The colors are red->green->blue. >> (define (shady pict) >> (dc (lambda (dc x y) >> ; get old brush >> (define b (send dc get-brush)) >> ; make new brush, only change gradient >> (define new-brush >> (new brush% >> [color (send b get-color)] >> [style (send b get-style)] >> [stipple (send b get-stipple)] >> [gradient (new linear-gradient% >> [x0 0] [y0 0] [x1 (* 2 r)] [y1 0] ; >> horizontal gradient >> [stops (list (list 0 red) ; (0,0) >> to ( r,0) red->green >> (list 1/2 green) ; (r,0) >> to (2r,0) green->blue >> (list 1 blue))])] >> [transformation (send b get-transformation)])) >> ; use new brush to draw the pict >> (send dc set-brush new-brush) >> (draw-pict pict dc x y) >> ; restore old brush >> (send dc set-brush b)) >> (pict-width pict) (pict-height pict))) >> >> (define-syntax (echo stx) (syntax-case stx () [(_ expr) #'(values 'expr >> expr)])) >> >> (newline) (newline) >> "Expected: A (black) rectangle" >> (echo (rect)) >> "Expected: A rectangle filled with nothing (default brush is empty)" >> (echo (fill (rect))) >> "Expected: A rectangle filled with linear gradient (red to green)" >> (echo (shady (fill (rect)))) >> "Expected: Two red-to-green rectangles" >> (echo (hc-append (shady (fill (rect))) (shady (fill (rect))))) >> "Expected: Two red-to-green rectangles" >> (echo (let () (define p (shady (fill (rect)))) (hc-append p p))) >> >> >> >> -- >> Jens Axel Søgaard >> >> ____________________ >> Racket Users list: >> <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> > > </div></div>-- -- Jens Axel Søgaard </blockquote></div> </div>