bitmap% performance

['racket' via users-redirect]

 

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 

[Simon Schlee]

Hi,

have you tried using read-bitmap? https://docs.racket-lang.org/draw/Drawing_Functions.html?q=read-bitmap#%28def._%28%28lib._racket%2Fdraw..rkt%29._read-bitmap%29%29

Personally I have only used the second constructor that takes a parameter named "in" here:

https://docs.racket-lang.org/draw/bitmap_.html

I didn't notice any performance problems, but my images have much lower resolution.

I resize my images by using the bitmap function which returns a pict, then using scale-to-fit, then using pict->bitmap to convert back to a bitmap.

Hope that is helpful,

otherwise you could provide an example that I can test on my computer, I am on linux.

Good luck!
Simon

[Robby Findler]

I don't know that we can help with the specific call you are reporting a slowdown for (maybe, but I won't address that here as asking other questions first seems worth doing). 

What are you using the bitmap for, exactly? Just to resize the bitmaps? Or as a backing store for drawing into the canvas? Something else?

Robby

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[Robby Findler]

(My reply to this post bounced on the attempt to send to OP.)

On Wed, Apr 22, 2020 at 3:39 PM 'racket' via users-redirect <us...@plt-scheme.org> wrote:

--

['racket' via users-redirect]

Hi Robby, thanks for your reply.

What are you using the bitmap for, exactly? Just to resize the bitmaps? Or as a backing store for drawing into the canvas? Something else?

Both of them. 

* I have more than 10K photos in 4000x3000 format that I’d like to download from a webdav server, read exif info, and resize to 960x720 and 320x240

* I should display the thumbnails in a canvas, keeping the system as smooth as possible while scrolling the canvas.

For the first task, if I don’t find any valid alternative, I could use some external tool to resize the images (let’s say libvips or imagemagick) or maybe write some ffi code to use libjpeg. I would prefer this solution over the first one, but I don’t have any experience with ffi coding.

Thanks,

Andrea  

[Robby Findler]

Thanks! For the first task I think you probably have to use the raw
bitmap% object (since I guess you're using `read-bitmap`). I'm not
sure if there could be some improvement internally so that screen
bitmaps were used to read in the jpegs. Absent an improvement at that
level, I guess I'd just try caching the conversions.

For the second, I guess you are creating very small bitmaps so
probably this particular creation issue isn't affecting that part? If
you really have a lot of them, you could probably implement some
clever pooling that wasn't keeping all of the jpegs in actual bitmap%
objects all the time but was just keeping ones that were likely to be
looked at soon in bitmap% objects.

hth,
Robby

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['racket' via users-redirect]

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 (sa...@cs.indiana.edu(mailto:sa...@cs.indiana.edu)) 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)

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['racket' via users-redirect]

> Thanks! For the first task I think you probably have to use the raw
> bitmap% object (since I guess you're using `read-bitmap`). 

Hi Robby, I don’t understand how to read a jpeg into a platform-bitmap. Probably I'm missing something in the documentation…  

> For the second, I guess you are creating very small bitmaps so
> probably this particular creation issue isn't affecting that part? If
> you really have a lot of them, you could probably implement some
> clever pooling that wasn't keeping all of the jpegs in actual bitmap%
> objects all the time but was just keeping ones that were likely to be
> looked at soon in bitmap% objects.

Yes, this is exactly what I’m doing. I’m preloading very small bitmaps in memory, display them to give to user a “preview", and then replacing them with a better version.

Andrea

[Robby Findler]

On Thu, Apr 23, 2020 at 1:14 PM 'racket' via users-redirect
<us...@plt-scheme.org> wrote:
>
> > Thanks! For the first task I think you probably have to use the raw
> > bitmap% object (since I guess you're using `read-bitmap`).
>
> Hi Robby, I don’t understand how to read a jpeg into a platform-bitmap. Probably I'm missing something in the documentation…

Right-- I agree that that isn't supported currently. I don't know how
difficult it would be to support.

Just a random thought: did you try using the read-bitmap method on the
already created bitmap? I don't know if that would be faster (I wanted
to try before posting but I didn't get there). It may be, however,
that the code inside bitmap% would have to be improved.

Robby