Bill Woodruff
10/24/2004 4:08:00 AM
V.S. .NET 1.1
I've found (to my surprise) that I can manipulate a large image (5456x9854 jpg
file 4.4 megs in size), panning it inside a Panel "viewport" using standard
mouse-down-and-drag techniques.
Performance is better than I thought (on a PIV 2.0 ghz machine with 1 gig of
memory) possible using managed code only. I have been unable to zoom this 2x
using the ImageResize api : although I am able to zoom up a file about half this
size. Zooming down in size is no problem.
Out of curiousity I've looked at the specs of 3rd. party imaging controls from
Pegasus and other companies. These packages are enormous collections of all
kinds of graphics functionality and priced accordingly.
I'd be very curious if anyone knows of a "small-profile" 3rd. party toolkit
focused on just panning and zooming very large images.
Second I'd be very curious to know if there are any resources (I haven't found
any yet in the usual places) for manipulating very large images using unmanged
code that might offer performance improvements or abilities to handle very large
files.
Bob Powell, as always a useful source, has some good resources on copying parts
of an image that could be used to reduce the "virtual working area" : but I do
believe you must first have the entire source image in memory.
I'm guessing you could do some neat code to read part of an external picture
file into a byte buffer and then coerce it into a Bitmap. Clearly at some point
of image size and complexity you reach the point where you would have to
implement a "banding" scheme as the old photo-typesetters I used to program in
PostScript did, and that is clearly to be avoided at an advanced age :)
Appreciate any ideas !
best, Bill Woodruff
dotScience
Chiang Mai, Thailand
"wisdom is when no one doubts your own hypotheses more than you do"