Hi Stefan, Nice Algorithm... it seems to fall into the class of 'median' style non-linear filters. These are very important in the x2 upscalers used in motion-adaptive deinterlacing in current mainstream Digital TV chips for flat panel displays. There are quite a few variations (every firm has to come up with their own to avoid the patents of other firms). The basic idea is just the one you came up with though: don't just pick a 'dumb' spatial average based on some signal theory that probably doesn't really apply too well to images. Instead try to come up with a pixel that is reasonably 'typical' (close to the mean / median) of a small 'context' around the sampling point.
For the same x2 special-case asd your algorithm there is also some very interesting work based on ideas from some Sony researchers. Here you again choose your weights dynamically based on context in which your new pixel appears. However, the weight-selection function you use constructed by a 'learning' process. You 'train' your 'smart filter' on a huge set of training data (upscaling downsampled video and trying to match the original as closely as possible). The results are sometimes eerily good! The training approach (and the larger 3x3 'context' they use) allows them to avoid certain kinds of artefact I (suspect) your technique might have in common with median-like non-linear scaling filters. The usual complaint is a tendency to optical 'fattening' of fine features. Median filters also tend to be expensive (in HW) to get to work for fractional scale factors. Though I suspect yours is quite 'friendly' in that regard. Also, in fairness to the 'dumb' signal theory approach in the 'real world' you *never* just apply a reconstruction filter alone. You always run some kind of adaptive sharpening as well to steepen the otherwise unprettily 'flat' transitions a linear reconstruction filter alone would give you. The combined results can also be pretty good and the technique has the advantage of robustness and that it is clean and efficient to implement in 'streaming' 1-pixel-per-cycle VLSI hardware. cheers, Andrew ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users