Re: bitmap% performance

Hi Sam,
trying your code I get back the following error:

load-file in bitmap%: not available in a canvas-compatible bitmap: (object:quartz-bitmap% ...)


The error I get is expected according to the load-file documentation:

"Loads a bitmap from a file format that read from in, unless the bitmap was produced by make-platform-bitmap, make-screen-bitmap, or make-bitmap in canvas% (in which case an exn:fail:contract exception is raised)"

Which racket version/platform did you use?

Andrea 





On 23 April 2020 at 18:39:08, Sam Tobin-Hochstadt ([email protected](mailto:[email protected])) wrote:

> I'm trying to understand the issue here. You say that you can't use
> `make-platform-bitmap` doesn't work, but this program works for me and
> loads two JPEGs into a platform bitmap.
>  
> #lang racket/base
> (require racket/draw racket/class)
> (define b (make-platform-bitmap 1000 1000))
> (define bs (make-bytes 100))
>  
> (send b load-file "/home/samth/Dropbox/punge-stuff/diploma.jpeg")
> (send b get-argb-pixels 20 20 5 5 bs)
> (bytes->list bs)
>  
> (send b load-file "/usr/share/doc/texlive-doc/dvipdfm/mwicks.jpeg")
> (send b get-argb-pixels 20 20 5 5 bs)
> (bytes->list bs)
>  
> On Wed, Apr 22, 2020 at 4:39 PM 'racket' via users-redirect
> wrote:
> >
> >
> > Hi,
> > I’m writing to the group looking for help with a performance issue.
> > I’m coding a gallery like application, using the racket/draw library, but the bitmap% class seems to be pretty slow. The (make-bitmap 4000 3000) operation takes more than 4 seconds on my computer (a macbook pro with a 3.1GHz dual core i5 and 16GB ram).
> > What I'd need to do is simply read and resize some jpeg files to display them in a canvas. I could use some external program to resize the photos but I would prefer to work with racket only. The make-platform-bitmap is 20 times faster than the make-bitmap, but I didn’t find a way to draw a jpeg on it.
> > Do you have any suggestion?
> >
> > Thanks,
> > Andrea
> >
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