RE: [XaraXtreme-dev] OSRenderRegion::DrawTransformedBitmap

["Charles Moir" <CharlesM@xxxxxxxx>]

I agree current thumbnail quality is terrible, and there are size /
position bugs in the bitmap gallery that have been there forever.

We dropped Phil's improvements because for documents with lots of large
bitmaps the system went at a crawl. It implied it was scanning vast
tracks of bitmap memory to generate thumbnails, and sometimes this is
VM. So just opening and scrolling the bitmap gallery became unusable.

So the immediate obvious answer is to cache the thumbnails, just as the
other galleries do IIRC (clipart gallery, font gallery) and I would have
thought it would have shared a lot of code with these areas. Perhaps
not?

Charles


> -----Original Message-----
> From: owner-dev@xxxxxxxxxxxxxxxx 
> [mailto:owner-dev@xxxxxxxxxxxxxxxx] On Behalf Of Phil Martin
> Sent: 27 April 2006 10:57
> To: dev@xxxxxxxxxxxxxx
> Subject: RE: [XaraXtreme-dev] OSRenderRegion::DrawTransformedBitmap
> 
> Alex,
> 
> In Xtreme we experimented with using GRenderRegions in the 
> bitmap gallery to improve the quality of the thumbnails. (The 
> quality of the thumbnails in the bitmap gallery using 
> OSRenderRegion is truly appalling
> - sticks out like a sore thumb to me...) This change was 
> removed before release of Xtreme because it was slower than 
> the OSRenderRegion equivalent but maybe that's not true under 
> wxWidgets.
> 
> We did this simply by changing 
> BitmapSGallery::CreateRenderRegion to call 
> CreateGRenderRegion instead of CreateOSRenderRegion. (And 
> similar change to DestroyRenderRegion.)
> 
> That might not suit because of the text rendering problem you 
> mention but it might be educational to try it. Maybe it 
> simpler to fix system text rendering in GRenderRegion than 
> attempting the things you are suggesting???
> 
> Phil
> 
> -----Original Message-----
> From: owner-dev@xxxxxxxxxxxxxxxx 
> [mailto:owner-dev@xxxxxxxxxxxxxxxx] On Behalf Of Alex Bligh
> Sent: 27 April 2006 10:38
> To: xara-dev
> Cc: Alex Bligh
> Subject: [XaraXtreme-dev] OSRenderRegion::DrawTransformedBitmap
> 
> I'm trying to fix up the above so the bitmap gallery 
> (inter-alia) works.
> 
> What it does is plots a KernelBitmap to the screen, having scaled it.
> You would have thought this would be simple, but no it's not.
> 
> Firstly, internally we appear to store our bitmaps (inside an 
> OilBitmap) in a format which is neither a wxImage or a 
> wxBitmap (fair enough as neither of those classes are 
> sufficiently flexible). So if I am taking the "use the OS" 
> route, I need to convert it to a wxImage in order to do any 
> processing on it at all. Cue a conversion to 32bpp and a 
> large amount of memory use.
> Also, cue stepping through the image pixel by pixel, which 
> doesn't seem fun.
> Next I need to resize it to the correct size as wx seems to 
> have no concept of StretchBlit (or more accurately its blit 
> code just calls the resize code anyway). Well, at least that 
> frees up most of the memory as these are just thumbnails. 
> Next, I need to convert it to a wxBitmap, which will 
> downsample the colour if necessary as I understand it. And 
> lastly, I need to plot it in the right place.
> 
> All this sounds a horribly memory-consumptive activity. Let's 
> say I have a 1bpp bitmap which is an A4 scan at 300dpi. 
> That's a quite reasonable 1Mb if my calculations are correct. 
> Just plotting the bitmap is going to cause 32Mb to be 
> allocated, filled, and removed, every time the bitmap is 
> redrawn in the gallery (or better yet, every time a rectangle 
> intersecting the bitmap is redrawn!). At 600dpi, that would 
> be a 128Mb memory allocation. And I hear the rescale call is 
> pretty useless too (lack of antialiasing).
> 
> I can't convert the whole thing over to use GRenderRegion as 
> the system text plotting stuff doesn't work there.
> 
> So I am left with the following cunning plan, which is 
> sufficiently disgusting I'd like a second opinion on it!
> 
> * Inside OSRenderRegion::DrawTransformedBitmap, create a new
>   GRenderRegion, which lasts only for the life of the call.
> 
> * The new GRenderRegion will either render directly to the 
> OSRenderRegion's
>   DC (or rather a copy of it), which I think will work, or if that
>   fails I'm left with GRenderBitmap (or whatever the equivalent call
>   is called) and converting the (scaled) bitmap to a 
> wxImage/wxBitmap or
>   possibly some new subclass of GRenderRegion which produces a
>   wxImage/wxBitmap directly.
> 
> * All the GRenderRegion's short life consists of is one call to
>   GRenderRegion::DrawTransformedBitmap, which will do the job properly
>   using GDraw (I hope).
> 
> Is this feasible? Is it disgusting? Should I be avoiding 
> using GRenderRegion (or gdraw as a whole) from 
> OSRenderRegion? Would we do better writing a fast call to 
> generate an arbitrary size wxImage (say) from a KernelBitmap?
> Do we indeed already have a similar call to this?
> 
> Alex
>