Re: [Interest] Improve ListView scrolling performance (many pictures)

@Mark: Sorry, that was probably a bit confusing. ;-) What I meant was the following: Whenever a new batch of images are received I resize and compress them a little bit to create thumbnails. After the images are resized and compressed, they are added to the ListModel. That's the part, that is

Re: [Interest] Improve ListView scrolling performance (many pictures)

Hi, I don't quite follow. First you say you implemented our suggestions (move image processing in a thread), then you say: "all operations are performed in the main (GUI) thread"... Exactly the opposite of what we've been suggesting. If i'm reading your reply correctly you're not offloading

Re: [Interest] Improve ListView scrolling performance (many pictures)

Yes - it's possible to move QImage processing to another thread. I've used QtConcurrent::run() to resize and write several images concurrently. void SomeClass::_writeImage( QImage inImage, const QString ) { QFuture future = QtConcurrent::run( [this, inImage, inPath] () { QImage image

Re: [Interest] Improve ListView scrolling performance (many pictures)

you should avoid any time consuming ops in his thread On Aug 13, 2017 22:40, "Bernhard B" wrote: > Many thanks guys! > > I just implemented your suggestions and have to say that the scrolling > performance definitely improved a lot. Thanks a lot for your help! > > However,

Re: [Interest] Improve ListView scrolling performance (many pictures)

Many thanks guys! I just implemented your suggestions and have to say that the scrolling performance definitely improved a lot. Thanks a lot for your help! However, as I am now doing more work (compress image + resize) before I populate the Listmodel, I noticed that there is a significant lag

Re: [Interest] Improve ListView scrolling performance (many pictures)

I've been using jpeg - something like this (where MAX_THUMB_DIM is 60): void _saveThumbnail( QImage inImage, const QString ) { QImage image = inImage.scaled( MAX_THUMB_DIM, MAX_THUMB_DIM, Qt::KeepAspectRatio, Qt::SmoothTransformation ); QImageWriter writer( inPath, "JPEG" );

Re: [Interest] Improve ListView scrolling performance (many pictures)

You need to do the "heavy" image operations in a separate thread! Copy the result back to the main thread and feed it to QML. You should not do any more operations on it once it lives in the main thread (no resize, scale, colorize, whatever) as you will notice that during scrolling. On Fri, Aug

Re: [Interest] Improve ListView scrolling performance (many pictures)

Hi Andy, many thanks for your response! I am also using a QAbstractListModel-derived class that gets exposed to the QML world which contains the images. Yesterday I started to resize the images before feeding them to the ListModel. According to the QML Profiler the delegate gets now created a

Re: [Interest] Improve ListView scrolling performance (many pictures)

Bernhard: I don't use QML, but in my application I use a QAbstractItemModel-derived class and a QTreeView-derived class to display image thumbnails in the view. The way I make it speedy is to save the image as a thumbnail so the view items don't need to resize the image data at all. Maybe you

Re: [Interest] Improve ListView scrolling performance (many pictures)

Hi Vlad, you mean the QQuickAsyncImageProvider? That one sounds really promising. Will definitely try that out. Many thanks for the suggestion! Bernhard Am Donnerstag, 10. August 2017 schrieb Vlad Stelmahovsky : > threaded image provider might help > > On Thu, Aug 10, 2017 at 12:36 PM,

Re: [Interest] Improve ListView scrolling performance (many pictures)

threaded image provider might help On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B wrote: > Hi, > > yesterday, I also tried to replace the Base64ImageProvider approach with a > subclassed QQuickPaintedItem which paints the image in it's paint method. I > imagined that this

Re: [Interest] Improve ListView scrolling performance (many pictures)

Hi, yesterday, I also tried to replace the Base64ImageProvider approach with a subclassed QQuickPaintedItem which paints the image in it's paint method. I imagined that this approach might be faster es no bade64 decoding needs to be done. But unfortunately it looks like as it's performing even