Mark Claassen wrote:
Thanks for all your help. I believe, though, that I didn't explain our
main reason for messing with this.
We were hoping to create a Component so that all the panning could be
done via the scroll bars, and not the arrow keys. The default zooming
behaviour just renders a piece of the image inside a Component.
Depending on how this is used, you might be able to see the whole
section, or have scroll bars which can be used to see the section. We
were wanting to have the scroll bars always set up so that the whole
document, regardless of zoom, could be navigated to with the scroll
bars.
The first way that came to mind was just to make the canvas bigger, and
render the whole image. This, however, took too much memory.
Ok, I see the problem now. We were using getSize() when we should
generally use getVisibleRect() to get the area we are actually going
to display (and hence the size of the offscreen buffers we should
create). I'm in the processes of fixing this.
The next way I thought we could do this would be to make the canvas as
big as we need for the whole image, but just paint the portion of the
canvas that is currently being viewed in the scroll pane.
Is there a way in Batik that I can accomplish this through the API you
mentioned?
You may also want to subclass JSVGCanvas and implement the scrollable
interface. Jan Lolling has posted code to do this several times.
As long as you do the scrolling by adjusting the rendering
transform the tile caching will kick in.
-----Original Message-----
From: Thomas DeWeese [mailto:[EMAIL PROTECTED]
Sent: Tuesday, August 12, 2003 4:46 AM
To: Batik Users
Subject: Re: Lazy rendering and zoom
Hi Mark,
Mark Claassen wrote:
Thanks for the reply.
Ok, so here is our theory:
1) Using the SVG view box and the scale factor, figure how
many tiles
(at say 100 X 100) will fit into the image.
2) Create a JSVGComponent (workingComp) and set the
preferred size to
be the size of our tiles (100 X 100)
3) Set the rendering transform of workingComp to have the
scale factor
we want
The point of my message was that if you zoom the canvas
with a static document it will automatically tile the image
for you. Try it, bring up an image with a really complex
background (try
samples/batikBatik.svg) Zoom in a bunch Pan right notice it
takes a second or two to update, Pan back left notice it
repaints immediately.
The biggest problem with the current scheme is that the
tile cache is extrememly limited in size it keeps ~50 128x128
tiles in memory (around 4MB - which is like one screenful of
data these days). This can be adjusted by making calls to:
org.apache.batik.ext.awt.image.rendered.TileCache.setSize(in sz);
The cache actually does use SoftReferences to try and
reclaim tiles that age out of the cache but these are
generally pretty quickly reclaimed. The number you provide
is the number of tiles it will hold hard references to.
---
In our paint method for our JComponent (myComp), we will paint the
tiles that are visible in our scrollpane.
For each visible tile
4) translate the rendering transform so that the part
of the tile we
want is on the workingComp
5) Draw this to a buffered image and keep it.
6) repaint this tile on myComp
Does this sound OK? Are there any obvious pitfalls or performance
issues that might make this not a practical solution?
The current system goes to great lengths to rendering
large 'patches' of the image at once and then split the data
out into tiles after the fact, this is significantly more
efficent then rendering each individual tile.
-----Original Message-----
From: Thomas DeWeese [mailto:[EMAIL PROTECTED]
Sent: Friday, August 08, 2003 6:29 PM
To: Batik Users
Subject: Re: Lazy rendering and zoom
Mark Claassen wrote:
Thanks for the reply.
As it turns out, we are using a static document already. We went
ahead and actually set the state to be static, but we
still get the
memory problem if we zoom enough. (It seems that we are
now able to
zoom a bit more, although this may just be a coincidence.)
From your
description, we thought it was futile to override the
createImageRenderer method as this point.
It seems to me that if the tiles are rendered lazily, we
could zoom
indefinitely and use a relatively constant amount of
memory. Also, we
have never noticed the document being painted as we
scroll. If the
tiles truley were rendered lazily, I would except to see this.
Maybe we are just doing something wrong. We weren't quite
sure how to
get the zoom we wanted using the API directly, so we resize
the canvas
to zoom. To zoom 2X, we:
Dimension d = canvas.getSize();
d.width = d.width * 2;
d.height = d. height * 2;
canvas.setPreferredSize(d)
canvas.revalidate();
Is there a better way?
Yes change the rendering transform, take a look at
Zoom(In|Out)?Action in JSVGCanvas.java you are actually
doubling the
size of the 'visible' canvas so it creates an offscreen that size.
-----Original Message-----
From: Thomas DeWeese [mailto:[EMAIL PROTECTED]
Sent: Friday, August 08, 2003 12:10 PM
To: Batik Users
Subject: Re: Lazy rendering and zoom
Mark Claassen wrote:
I noticed there is a setProgressivePaint(boolean) method in
JGVTComponent. This seems to display items on the canvas
as they are
rendered, and not just display the whole document at once.
What I was wondering was if there is an option that goes a step
further, and would restrict rendering to just viewable
area. This is
a common thing in Swing, where, for instance, the rows of a
table that
are not currently visible in a JScrollPane are never rendered.
The default zooming behaviour in Batik seems to render a
portion of
the document while not changing the canvas size. We
would like to
change the canvas size, so that the we can pan to see any
part of the
document we need simply by moving the scrollbars.
Unfortunately, this
causes OutOfMemory errors when the zoom factor gets large.
I know we can increase the JVM heap size, but this can only
go so far.
What I was hoping for was something in the JSVGCanvas that
would draw
just a portion of the document on the canvas, and then when
a scroll
occurred, it would noticed that this area had not been
rendered and
draw that. One could even go so far as to anticipate the
loading of
sections and use SortReferences to hold now longer visible
sections.
Is there anything like this, or any plans to include
something like
this?
Hi Mark,
This is already done for Static Documents. The
Static Renderer
keeps a tiled view of the image and when translates
happen it tries
to populate the new view from the stored tiles. This is
generally
not done for dynamic documents as maintaining the tile store is
expensive for many small changes (the system would widens
rendering
requests to tile
boundries) also there were a few bugs in what I will call odd
cases (the size/location of the root SVG changing). However
depending on your context this still might be a win for your
case. It is pretty easy to change this by overiding the
following method in batik.swing.svg.JSVGComponent:
protected ImageRenderer createImageRenderer() {
if (isDynamicDocument) {
return rendererFactory.createDynamicImageRenderer();
} else {
return rendererFactory.createStaticImageRenderer();
}
}
So it always returns a static ImageRenderer.
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