Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
Smooth scrolling zoom in draw widget; how?
I use a scrollable draw widget to display large images (up to 2048x2048) at full resolution (viewport is 512x512 or 1024x1024 depending on screen resolution). The problem is: users want to zoom into images and keep the smooth scrolling viewport for the expanded image . If I simply blow up my image by the required factor, the size will quickly increase beyond the computers memory. I thought about keeping the original byte scaled image as byte array or as pixmap. For each viewport scroll event I would calculate the portion of the zoomed image to display from the current viewport coordinates. Then I would take the respective subarray of the image and extend it using rebin(subarr, view_port_x, view_port_y, /sample) and finally display it in the viewport. I doubt that this is efficient enough to provide the illusion of smooth scrolling. Has anybody a better idea? Karl -- -- IPP, PO Box 1533 | Phone: +49-89-3299-1655 | E-Mail: D-85740 Garching | FAX : +49-89-3299-1149 | krieger@ipp.mpg.de
In article <33A960A1.17B7@astrosun.tn.cornell.edu>, JD Smith <jdsmith@astrosun.tn.cornell.edu> writes: > In my case, I was smoothing a positive definite > image, and the smoothed image contained bands of negative values! I > think arrays which contain a wide dynamic range of values are most > susceptible. Converting to double precision seems to solve the problem, Maybe it's an overflow like in IDL> print,32767+10 -32759 Shure this would be a bug, but it explains the behaviour Peter -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~ Peter "Pit" Suetterlin http://www.uni-sw.gwdg.de/~pit Universitaets-Sternwarte Goettingen Tel.: +49 551 39-5048 pit@uni-sw.gwdg.de -- * -- * ...-- * -- * ...-- * -- * ...-- * -- * ...-- * -- * ...-- * -- Come and see the stars! http://www.kis.uni-freiburg.de/~ps/SFB Sternfreunde Breisgau e.V. Tel.: +49 7641 3492 ____________________________________________________________ ______________