Re: [plt-dev] Re: [plt-scheme] scaling and rotating images using image.ss
This should be (overlay/places "center" "middle" (rotate 0 a) (rotate 20 a) (rotate 40 a) (rotate 60 a)) not .. "middle" "middle" ... correct? On Nov 14, 2009, at 1:18 AM, John Clements wrote: > > On Sep 26, 2009, at 6:29 AM, Matthias Felleisen wrote: > >> >> >> 1. htdp/world is deprecated, use 2htdp/universe instead. >> >> 2. we consider the pinhole approach to our image library as a mistake. To >> solve the problem Robby is working on 2htdp/image, a replacement for the >> image library. When it comes out (end of semester probably) it will support >> rotate and other such operations, plus comparisons will be much faster. > > I'm surprised to say it, but right now I'm *really missing the pinhole*. > > I'm trying to write a function in 2htdp/image that draws, say, 36 copies of a > shape arranged in a big "circle" around a center. With pinholes, this was > easy. Move the pinhole way off to the left, then rotate the thing around the > pinhole by 10 degrees, 20 degrees, etc. Overlay them all, and you're done. [*] > > With the new approach, I'm finding this nearly impossible. The natural > approach involves, for instance, putting the thing "beside" a long horizontal > space, and then rotating it. The problem is that it doesn't rotate about a > fixed point. To see the problem, consider this program: > > (require 2htdp/image) > > (define a (beside (rectangle 150 2 "solid" "black") (ellipse 10 50 "solid" > "purple"))) > > (overlay/places "middle" "middle" >(rotate 0 a) >(rotate 20 a) >(rotate 40 a) >(rotate 60 a)) > > The problem is that mapping a point in the pre-rotation shape to a point in > the post-rotation shape is hard. > > ... > > After wrestling with this for quite a while, I have a solution of sorts; you > have to overlay the shape you want to rotate on a large outline circle in > such a way that the shape is entirely inside the circle. Rotating this shape > does not change the bounding box at all, meaning that you can overlay them > correctly. Needless to say, computing the size of the circle required is a > big pain. > > E.G.: > > (define b (overlay/xy (circle 200 "outline" "blue") 200 200 a)) > > (overlay > (rotate 0 b) > (rotate 20 b) > (rotate 40 b) > (rotate 60 b)) > > Am I missing something obvious? > > John > > [*] with the obvious caveat that the old version didn't rotate shapes at all. > > > _ > For list-related administrative tasks: > http://list.cs.brown.edu/mailman/listinfo/plt-dev _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
Re: [plt-dev] Re: [plt-scheme] scaling and rotating images using image.ss
middle and center are synonymous (and can be used in both horizontal and vertical directions). Robby On Sat, Nov 14, 2009 at 10:42 AM, Matthias Felleisen wrote: > > This should be > > (overlay/places "center" "middle" > (rotate 0 a) > (rotate 20 a) > (rotate 40 a) > (rotate 60 a)) > > not > > .. "middle" "middle" ... > > correct? > > > On Nov 14, 2009, at 1:18 AM, John Clements wrote: > >> >> On Sep 26, 2009, at 6:29 AM, Matthias Felleisen wrote: >> >>> >>> >>> 1. htdp/world is deprecated, use 2htdp/universe instead. >>> >>> 2. we consider the pinhole approach to our image library as a mistake. To >>> solve the problem Robby is working on 2htdp/image, a replacement for the >>> image library. When it comes out (end of semester probably) it will support >>> rotate and other such operations, plus comparisons will be much faster. >> >> I'm surprised to say it, but right now I'm *really missing the pinhole*. >> >> I'm trying to write a function in 2htdp/image that draws, say, 36 copies of >> a shape arranged in a big "circle" around a center. With pinholes, this was >> easy. Move the pinhole way off to the left, then rotate the thing around >> the pinhole by 10 degrees, 20 degrees, etc. Overlay them all, and you're >> done. [*] >> >> With the new approach, I'm finding this nearly impossible. The natural >> approach involves, for instance, putting the thing "beside" a long >> horizontal space, and then rotating it. The problem is that it doesn't >> rotate about a fixed point. To see the problem, consider this program: >> >> (require 2htdp/image) >> >> (define a (beside (rectangle 150 2 "solid" "black") (ellipse 10 50 "solid" >> "purple"))) >> >> (overlay/places "middle" "middle" >> (rotate 0 a) >> (rotate 20 a) >> (rotate 40 a) >> (rotate 60 a)) >> >> The problem is that mapping a point in the pre-rotation shape to a point in >> the post-rotation shape is hard. >> >> ... >> >> After wrestling with this for quite a while, I have a solution of sorts; you >> have to overlay the shape you want to rotate on a large outline circle in >> such a way that the shape is entirely inside the circle. Rotating this shape >> does not change the bounding box at all, meaning that you can overlay them >> correctly. Needless to say, computing the size of the circle required is a >> big pain. >> >> E.G.: >> >> (define b (overlay/xy (circle 200 "outline" "blue") 200 200 a)) >> >> (overlay >> (rotate 0 b) >> (rotate 20 b) >> (rotate 40 b) >> (rotate 60 b)) >> >> Am I missing something obvious? >> >> John >> >> [*] with the obvious caveat that the old version didn't rotate shapes at all. >> >> >> _ >> For list-related administrative tasks: >> http://list.cs.brown.edu/mailman/listinfo/plt-dev > > _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
Re: [plt-dev] Re: [plt-scheme] scaling and rotating images using image.ss
On Nov 14, 2009, at 11:46 AM, Robby Findler wrote: > middle and center are synonymous (and can be used in both horizontal > and vertical directions). Then consider this a bug report/feature request. Like in HTML, I suggest that middle and center work for vertical and horizontal alignment, respectively. -- Matthias > > Robby > > On Sat, Nov 14, 2009 at 10:42 AM, Matthias Felleisen > wrote: >> >> This should be >> >> (overlay/places "center" "middle" >>(rotate 0 a) >>(rotate 20 a) >>(rotate 40 a) >>(rotate 60 a)) >> >> not >> >> .. "middle" "middle" ... >> >> correct? >> >> >> On Nov 14, 2009, at 1:18 AM, John Clements wrote: >> >>> >>> On Sep 26, 2009, at 6:29 AM, Matthias Felleisen wrote: >>> 1. htdp/world is deprecated, use 2htdp/universe instead. 2. we consider the pinhole approach to our image library as a mistake. To solve the problem Robby is working on 2htdp/image, a replacement for the image library. When it comes out (end of semester probably) it will support rotate and other such operations, plus comparisons will be much faster. >>> >>> I'm surprised to say it, but right now I'm *really missing the pinhole*. >>> >>> I'm trying to write a function in 2htdp/image that draws, say, 36 copies of >>> a shape arranged in a big "circle" around a center. With pinholes, this >>> was easy. Move the pinhole way off to the left, then rotate the thing >>> around the pinhole by 10 degrees, 20 degrees, etc. Overlay them all, and >>> you're done. [*] >>> >>> With the new approach, I'm finding this nearly impossible. The natural >>> approach involves, for instance, putting the thing "beside" a long >>> horizontal space, and then rotating it. The problem is that it doesn't >>> rotate about a fixed point. To see the problem, consider this program: >>> >>> (require 2htdp/image) >>> >>> (define a (beside (rectangle 150 2 "solid" "black") (ellipse 10 50 "solid" >>> "purple"))) >>> >>> (overlay/places "middle" "middle" >>>(rotate 0 a) >>>(rotate 20 a) >>>(rotate 40 a) >>>(rotate 60 a)) >>> >>> The problem is that mapping a point in the pre-rotation shape to a point in >>> the post-rotation shape is hard. >>> >>> ... >>> >>> After wrestling with this for quite a while, I have a solution of sorts; >>> you have to overlay the shape you want to rotate on a large outline circle >>> in such a way that the shape is entirely inside the circle. Rotating this >>> shape does not change the bounding box at all, meaning that you can overlay >>> them correctly. Needless to say, computing the size of the circle required >>> is a big pain. >>> >>> E.G.: >>> >>> (define b (overlay/xy (circle 200 "outline" "blue") 200 200 a)) >>> >>> (overlay >>> (rotate 0 b) >>> (rotate 20 b) >>> (rotate 40 b) >>> (rotate 60 b)) >>> >>> Am I missing something obvious? >>> >>> John >>> >>> [*] with the obvious caveat that the old version didn't rotate shapes at >>> all. >>> >>> >>> _ >>> For list-related administrative tasks: >>> http://list.cs.brown.edu/mailman/listinfo/plt-dev >> >> _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
Re: [plt-dev] Re: [plt-scheme] scaling and rotating images using image.ss
On Sat, Nov 14, 2009 at 11:49 AM, Matthias Felleisen wrote: > > On Nov 14, 2009, at 11:46 AM, Robby Findler wrote: > >> middle and center are synonymous (and can be used in both horizontal >> and vertical directions). > > > Then consider this a bug report/feature request. Like in HTML, I suggest that > middle and center work for vertical and horizontal alignment, respectively. > -- Matthias UGH! I vote for the "synonymous" version. Why should users -- especially students -- have to remember which is which? Especially when the words mean the same thing. --Carl _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
Re: [plt-dev] Re: [plt-scheme] scaling and rotating images using image.ss
On Sat, Nov 14, 2009 at 10:49 AM, Matthias Felleisen wrote: > > On Nov 14, 2009, at 11:46 AM, Robby Findler wrote: > >> middle and center are synonymous (and can be used in both horizontal >> and vertical directions). > > > Then consider this a bug report/feature request. Like in HTML, I suggest that > middle and center work for vertical and horizontal alignment, respectively. > -- Matthias > They do work for vertical and horizontal alignment. You want errors? Robby _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
Re: [plt-dev] Re: [plt-scheme] scaling and rotating images using image.ss
On Nov 14, 2009, at 11:55 AM, Robby Findler wrote: > On Sat, Nov 14, 2009 at 10:49 AM, Matthias Felleisen > wrote: >> >> On Nov 14, 2009, at 11:46 AM, Robby Findler wrote: >> >>> middle and center are synonymous (and can be used in both horizontal >>> and vertical directions). >> >> >> Then consider this a bug report/feature request. Like in HTML, I suggest >> that middle and center work for vertical and horizontal alignment, >> respectively. -- Matthias >> > > They do work for vertical and horizontal alignment. You want errors? Yes I thought we wanted errors but Carl's probably right. Why should we care about HTML and the people who teach HTML. _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
