Hi Jeremy,
The intention could be /to pass through/ if the value of hints is
different from the needed ones. That is the filter activates if and only
if |hints == neededHints|, otherwise it doesn't do anything and forwards
calls to its superclass.
--
Regards,
Alexey
On 17/04/2023 09:53, Jeremy Wood wrote:
I could be mistaken, but it looks like AreaAveragingFilter has a typo
in it. This method looks suspicious to me:
public void setHints(int hints) {
passthrough = ((hints &neededHints) !=neededHints);
super.setHints(hints);
}
Later on the passthrough field is used as:
public void setPixels(int x,int y,int w,int h,
ColorModel model,byte pixels[],int off,
int scansize) {
if (passthrough) {
super.setPixels(x, y, w, h, model, pixels, off, scansize);
}else {
accumPixels(x, y, w, h, model, pixels, off, scansize);
}
}
This makes me think we want passthrough to be /true/ when we match
specific hints (“neededHints”) promising to deliver the pixel data in
whole scanlines from top-to-bottom. So the “!=“ in setHints(..) should
be “==“.
If I set passthrough to true for BufferedImages (which always deliver
pixels from top to bottom in entire scanlines), then the execution
time of this filter reduces to less than 5% of its current time. But
it introduces scaling artifacts and looks lower quality.
So if (?) my theory is correct that there is a typo, and knowing that
the AreaAveragingFilter iseffectively internally deprecated
<https://bugs.openjdk.org/browse/JDK-6196792?jql=status = Open AND
text ~ "AreaAveragingScaleFilter"> : is anyone interested in
discussing this with me further? I attached my (very rough) test
program that demonstrates both the performance difference and the
scaling artifacts.
(My broad goal is to create thumbnails of large images. If I used a
Graphics2D to scale the image more than 50%, then I also see scaling
artifacts with that approach. I know “Filthy Rich Clients” outlined a
solution to that problem, but it’s expensive. So I’m dusting off this
filter to see if it can work.)
Regards,
- Jeremy
