There are really 2 questions here:
- How do I manipulate a BufferedImage without interfering with its
ability to be accelerated under the covers?
- Is there a type of image that lives in hardware accelerated memory and
to which I can write directly to its pixels?
To answer the first question, first note that the type of hardware
acceleration provided by a BufferedImage is very limited. It is what we
call a "managed image" which means that we can cache a copy of that
image in display memory if you copy it there frequently, but that copy
in the display memory is not where the pixels live - it is only a cached
copy. To avoid interfering with this "managed image" mechanism, you
would currently have to use the relatively high level methods on
BufferedImage and Raster and these are not as fast as manipulating the
pixel array directly. This concern doesn't really apply to your case,
though, since you modify all of the pixels in the image each time you
copy it to the screen and a managed image only provides benefit on the
second and subsequent times you render it to the screen. (The first
time you render it to a screen or VolatileImage, the data must be
uploaded to the display card whether it is going directly to the
screen/VolatileImage or whether it is going to the cached copy. Either
way, you still pay the performance penalty to get the pixels across the
bus to the card.)
The answer to the second question is that we currently have no image
type which has directly accessible pixels and which also lives in
accelerated memory - sort of an "uploadable texture" type of object.
That kind of image is on our wish list, but we have no schedule for
delivery of it yet...
...jim
This is my applet prototype:
=========================================================
public class Viewer extends Applet implements Runnable {
int[] idata = null; // image pixel data array
Image view = null; // viewport
int[] vdata = null; // view data array
Image offImage = null; // Offscreen rendering image
Graphics offGraphics = null; // Offscreen rendering graphics context
int offwidth = 0; // Width of the offscreen graphics
int offheight = 0; // Height of the offscreen graphics
MemoryImageSource source = null; // View is calcaulated here before dispaly
public Viewer() {
// use PixelGrabber to read pixels data into
// idata array
init();
}
public void init() {
// some init code
idata = readImagePixelData(imageFileName);
}
public void update(Graphics g) {
paint(g);
}
public void paint(Graphics g) {
// Setup offscreen rendering environmnent
offwidth = getWidth();
offheight = getHeight();
offImage = createImage(offwidth, offheight);
offGraphics = offImage.getGraphics();
vdata = new int[vwidth * vheight];
source = new MemoryImageSource(vwidth, vheight, vdata, 0, vwidth);
source.setAnimated(true);
view = createImage(source);
// read pixel data from idata and
// use some warp transform to
// extract a new view according
// to user input
transform(idata, vdata, mouse_x, mouse_y);
source.newPixels();
offGraphics.drawImage(view, 0, 0, this);
g.drawImage(offImage, 0, 0, this);
}
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