On 20/04/16 00:08, Phil Race wrote:
I've gone up and down the API (and most of the implementation)
ResolutionVariantItem is really only used in the public API in one
place :-
ImageProducer defines :-
+ default List<ResolutionVariantItem<ImageProducer>>
getResolutionVariantItems() {
+ return Arrays.asList(new ResolutionVariantItem<>(this, 1, 1));
The sort-of second place is that FilteredImageSource over-rides this.
The rest is the internal uses of the class (and its definition of course)
So do we need such a generic sounding API class for this one case, (or
are there other API-level uses?) and is there a different approach
which avoid the new class entirely ?
The ResolutionVariantItem class in this case is used to provide scale
factors for the ImageFilter and MediaTracker.
If we want to avoid this class it is necessary to understand from
which place these scale factors can be obtained.
The MultiResolutionImage has just getResolutionVariant(width, height)
method which allows to provide an image either from a set of resolution
variants or just generating an image with requested size.
It seems that generation an image for requested size is not an option
for multi-resolution Toolkit image just because it can be loaded by
MediaTracker.
MediaTracker.addImage(Image, id, width, height) method needs to load
all resolution variants from the provided multi-resolution image. First
it means that there should be finite number of them. The second is that
for passed width and height argument it needs to calculate size for the
resolution variants which are not loaded yet.
This is the first place where the scale factors need to be provided
with resolution variant:
MediaTracker.addImage(mriImage, id, w, h) ->
MediaTracker.addImage(resolutionVariant, id, w * rvScaleX, h * rvScaleY)
The second place where the resolution variant scales are used is
SunGraphics2D.drawImage() method when it draws a multi-resoltion image
with an applied filter.
Image mrImage = // create a multi-resolution image
ImageProducer filteredImageSource = new
FilteredImageSource(mrImage.getSource(), filter);
Image filteredImage = toolkit.createImage(filteredImageSource);
SunGraphics2D.drawImage() calls getResolutionVariant(mrImage, ...)
method to get a resolution variant with the requested destination width
and height to draw it. The resolution variant in this case is just a
ToolkitImage which source is FilteredImageSource an filter is a scaled
filter:
toolkit.createImage(new
FilteredImageSource(resulutionVariant.getSource(),
filter.getScaledFilterInstance(scaleX, scaleY)))
And the question is where the the scale factors can be obtained for
this case?
If there are others way to provide scale factors for the described
cases it will allow to not use new classes like ResolutionVariantItem.
Thanks,
Alexandr.
Assuming ResolutionVariantItem is the right name - and design - it
seems like it could use a bit more class javadoc, even if it is basically
a bag to hold a few things.
There are few formatting/typo things I noticed but no point in talking
about
those until the rest is near conclusion.
-phil.
On 04/05/2016 07:30 AM, Alexander Scherbatiy wrote:
Hello,
Could you review the fix:
bug: https://bugs.openjdk.java.net/browse/JDK-8152309
webrev: http://cr.openjdk.java.net/~alexsch/8152309/webrev.00
The purpose of the fix is to allow to apply an image filter for a
multi-resolution image to get new multi-resolution image so the code
below works without changes:
----------
Image mrImage = getMultiResolutionImage();
ImageProducer mriProducer = new
FilteredImageSource(mrImage.getSource(), new CropImageFilter(x, y, w,
h));
Image filteredMRImage =
Toolkit.getDefaultToolkit().createImage(mriProducer);
----------
The Image producer needs to be updated to contain a set of
resolution-variant image producers. It can be done introducing a new
MultiResolution[Image]Producer interface. However, the
FilteredImageSource which takes an original image producer as a
constructor argument needs to be declared as
MultiResolution[Image]Producer even for ordinary image producers.
I chose to add the getRVProducers() method directly to the
ImageProducer interface.
The option to add a method which request a resolution variant
producer for the given image size (getRVProducer(width, height) )
seems is not possible because the result multi-resolution image can
be loaded by a MediaTracker which can load only finite number of
resolution variants.
Applying an image filter to resolution-variant producers requires to
scale filters which use fixed image size (like CropImageFilter and
ReplicateScaleFilter).
There should be a way to get a scaled filter using the original one.
The resolution variant image producer need to provide necessary scale
factors for the used filter.
To do that getScaledFilterInstance(scaleX, scaleY) method is added to
the ImageFilter and public ResolutionVariantItem class which can hold
image or image producer with associated scale factors is introduced.
There is an interesting problem in SunGraphics2D where a
multi-resolution image size is requested. To do that it is necessary
to have an image observer which needs to redirect calls to the base
image observer. The resolution variant observer needs to know scale
factors to recalculate given [x, y, width, height] values. The scale
factors are provided by toolkit multi-resolution image but for non
toolkit multi-resolution images they need to be calculated dividing a
rv-image size to base image size. It looks like a closed loop when to
know scale factors it needs to get a rv-image size but for this it is
necessary to use an image observer which requires scale factors.
The current fix just divides rv-image size to base image size for non
toolkit multi-resolution images to get scale factors .
Thanks,
Alexandr.
