I am using the OpenGL Image sample code to open a panorama image
with dimensions 7000+
X 3000+ pixels. It leaves a big rectangle of black area on the
top left area when displaying in
the window. I open the same image in qtgraphics QuickTime sample
code and the image
displays fine in the window. Although the code used in both these
sample code uses Graphic
Importer component to draw the only difference is that in the
qtgraphics renders the image to
a window and the OpenGL image sample code renders the image to a
GWorld created using
QTNewGWorldFromPtr.
Is there a difference between the GWorld created by QTNewGWorld
and NewGWorld variants
and the one that is created for the window by NewCWindow?
There really shouldn't be any difference between the ports created
by all of these methods, unless you are using different pixel
formats. QTNewGWorld allows you to create GWorlds with pixel
types that that QuickDraw doesn't understand.
I realize that the rowBytes parameter is a limiting factor of
GWorld, but is there a way to work around this?
At 7000 pixels wide your rowBytes should be somewhere in the
neighborhood of 28000. This is certainly a small enough number to
fit into a long valued variable like the rowBytes. How do you
find the "rowByes" parameter to be a limiting factor?
It seems to me that rowBytes in a QuickDraw PixMap is a short (16
bits) and the max value is 0x7FFF but I remember from some the OS8
sources that you can not create RGB pixmap with more than 4000 points.
Rowbytes was indeed a short in a PixMap, but the top two bits were
used as flags, and so as a result, the maximum rowbytes was 0x3fff,
so 16383/4 gives you a hard limit 4095 for 32 bit pix (and less once
you took into account padding that was done).
However, "extended" pixmaps (introduced in OS 9?) had a separate
field for things like this, and it was declared as a long (and "was"
being the key word here - it was only exposed in one version of the
headers) so using a gworld as wide as one would reasonably want has
been doable ever since (there were some minor limitations with
certain printer drivers in OS 9, but again, that was "back in the day").
Glenn Andreas email@hidden
<http://www.gandreas.com/> wicked fun!
Widgetarium | the quickest path to widgets
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