Ping anyone?
On Mon, Jul 18, 2016 at 10:24 AM, Albert Astals Cid <albert.ast...@canonical.com> wrote: > There is a problem when trying to optimally[*] show an Image with > PreserveAspectCrop fillMode. > [*]optimally => as best looking as possible while using as litte > memory as possible > > You can see that problem in the screenshot at http://i.imgur.com/LSSlFEB.png > that corresponds with the code at http://paste.ubuntu.com/19480453/ > > As you can see when displaying a landscape (width > height) image in a > square Image Item the optimal way > is to set the source size height only, but if the image is portrait > (height > width) then the optimal way > is to set the source size width only. > > The requirement my program has is to have the best rendering quality > and memory usage for Image Items using PreserveAspectCrop. > Image sources are totally arbitrary, they can be from disk, from the > internet or even from QQuickImageProviders > (since we are plugin based and plugins can bring their own > QQuickImageProvider) > > This can be fixed in several ways. > > Workaround A > ********** > Changing the Image Item source size comparing the aspect ratio of the > image file with the one Image Item. > > You can see an implementation of that workaround at > http://bazaar.launchpad.net/~unity-team/unity8/trunk/view/head:/plugins/Dash/CroppedImageMinimumSourceSize.qml > > The problem with this workaround is that half of the times you end up > loading the image a second time. > This means extra CPU and potentially network usage. > > > > Workaround B > ********** > Implementing your own image provider that does compare the aspect > ratios before loading the image. > > You can see a partial implementation of this workaround at > https://code.launchpad.net/~aacid/unity8/croppedImageMinimumSourceSizeProvider/+merge/300176 > > There are two problems with this workaround: > * You end up implementing quite a bit of duplicated functionality > from qquickpixmapcache.cpp > * For the chained image providers (i.e. the original source was an > image provider url) you > still have to query the image provider twice half of the times > > > > Solution > ******** > Implementing the change in QtQuick internals so that when > PreserveAspectCrop fillMode is used > together with a sourceSize that has both width and height it does > return the optimal image > > You can see a work in progress implementation of this solution at > https://codereview.qt-project.org/#/c/165299/ > And how the previews could would look at > http://i.imgur.com/NRoXNzy.png (notice how the last column now is good > in both cases) > > There are two issues with this solution: > * It's a small behaviour change (but in my opinion for the better) > * Needs new api for the QQuickImageProvider to be able to implement > it, so we either need the proposed > QQuickImageProviderV2 or with a new "bool > shouldPreserveAspectRatioCrop(url, requestSize)" getter in the > existing QQuickImageProvider API > > > > All in all I think the solution i propose for QtQuick is acceptable > but i would like some agreeing that is fine adding new API before > finishing the patch. _______________________________________________ Development mailing list Development@qt-project.org http://lists.qt-project.org/mailman/listinfo/development
