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Optimized storage of 1BPP images [message #14033]

Thu, 07 February 2008 13:30

mdelfede
Messages: 1307
Registered: September 2007

Ultimate Contributor

I made a Tiff viewer control, with thumbnails and contiuous page scolling, in order to view Tiff images that are all 1 bit per pixel ones (black and whte fax).

I tried in 2 ways :

1- As explained here :

http://www.ultimatepp.org/forum/index.php?t=msg&th=3131& amp;start=0&

the image is rescaled on the fly zooming, panning and/or resizing the widget. The performance is not bad at all, but being the image very big the user feels like the scroll is a bit coarse.

2- The same but caching rescaled images when first displaying them. Of course, I must re-cache them on zooming. That works great, the scroll is very smooth but the cached images get *very* big in memory, with high zoom factors (I must cache the whole image because of pan/scroll requirements). In addition, when the zoom factor is high, there's a noticeable delay when rescaling/buffering the whole image.

As the images are just 1-bit-per-pixel, I think is nonsense to store them in RGBA format; it would be much better to have a packed 1BPP format... that would solve all problems.
Is there an (easy!) way to get image through ImageEncoder that are so packed, and of course a way to draw those packed images
directly on a Draw object ?

Ciao

Max

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