the preview widget

[Boudewijn Rempt]

On Tuesday 21 June 2005 14:16, Casper Boemann wrote:
> Hi
>
> As you might have noticed I have changed the layout of the preview, to look
> more like digikam.
>
> Now the preview widget itself also needs some updating:
>  - zoom doesn't exist in the digikam preview - the image is zoomed all out
>  - that doesn't mean we shouldn't keep the abillity to zoom, but I think
> default should be zoomed out as in digikam.

Agreed. We should show all of the image in our preview.

>  - the update of the preview seems slow. Is the algorithm as effective as
> it can be?

No, definitely not. In fact, if I remember correctly, preview copies & renders 
the complete image. Options are:

* Just preview the active layer, out of context
* Copy the image, scale it down, and then render it. Cache the scaled-down 
thumbnail.
* Work on the QImage of the rendered image, and apply all filters on that -- 
for preview, that may be accurate enough.

Note that we want a fast thumbnail preview for in the bird's eye box, too, and 
in the variations dialog we need a whole bunch of previews. So I guess the 
requirements are:

* Frugal with memory
* Fast
* Filters should work on the preview image
* Zoomable, but initially the complete image/layer is shown
* Selectable: preview layer/preview image

I have a feeling that this may be hard to achieve...

> This is not something I'm going to do, but I think we should discuss it and
> put it in the TODO.

Definitely. 

-- 
Boudewijn Rempt 
http://www.valdyas.org/fading/index.cgi
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