Ian Collier wrote: >On Tue, Mar 02, 1999 at 01:54:37PM +0000, Andrew Collier wrote: >> Well, if it's that much of a problem, replace JPG with PICT and you'll get >> the original, non-lossily compressed image (providing you have something >> which can read PICTs, of course). > >Those do look better than the jpegs, actually. It might give a better >result if you sample down to 8-bit (without dithering) and GIF them rather >than using jpeg. I might try this at some stage.
Right... there now exist GIF files of everything, too. With varying degrees of success.... At some point I'll prodive an alternative index.html which links to the other file types. >The images seem quite >dark, btw. This may be a function of display gamma, since I've speculated >before that your display is gamma corrected while most other kinds of >display (except SGIs) are not. Yes it is - and will you stop trying to tell me that this is a fault at my end!! >> The images always DO >> have more than 16 colours, because there is an antialiasing between pixels; >> remember Sam's pixels are actually rectangular instead of square, so there >> can _never_ be an exact 1:1 mapping without distorting the shape of the >> picture. > >Does the TV card give a good enough resolution to be able to squash it >and get an exact 1:1 mapping? (If so then stretching it back again could >be the job of the viewer.) Well sort of. But I've said before, I'm not hugely concerned with getting flawless picture quality - and I've spent long enough already taking over 175 framegrabs, so perhaps redoing them can be *your* project over Easter while I'm revising... >> The basic problem is that my TV >> card munges adjacent horizontal lines together, so the images will always >> be blurred. > >If it does this in a predictable way then it might be possible to reverse >the effect. On the other hand, from a brief look at some pictures it doesn't >seem to have been done in any kind of logical manner. (Why haven't you sent >it back?) It is totally predictable, and I should imagine it is not recoverable. It throws away every alternate frame, and averages the pixels in each pair of adjacent horizontal lines. It then scales whatever picture from the signal is left, to the size of the window which, by default, is 320x240. It can go up to 640x480. When watching real TV pictures, this either doesn't happen or is at least not noticable. My guess is that the card gets confused by the lack of interlacing, and I can hardly take it back on the basis of it being slightly confused by a rather non-standard signal. Strangely enough, I can get a less munged picture by telling the card that the composite input is in fact an NTSC signal, but unfortunately I only get to see the top-left corner two thirds of the screen. Andrew -- | Andrew Collier | email [EMAIL PROTECTED] | Talk sense to a | Part 2 NatSci | http://carou.sel.cam.ac.uk/ | fool and he +----------------+-----------------------------+ calls you foolish | Selwyn College Student Computer Support Team | -- Euripides
