"Smooth" scaling produces blurry images after calling image.getImageData().clone()

[tobiasmelcher]

• I verified I can reproduce this issue against I20250413-1800

Steps to reproduce

From a fresh installation and clean workspace:

• download the attached sample plugin, extract it, import into workspace and run target platform
  simple.zip
• open the "Sample view" provided by the simple plugin in the target platform
• icons in the tree viewer are blurry and not sharp
  

Images are no longer blurry after disabling the setting "Use monitor-specific UI scaling" (https://eclipse.dev/eclipse/news/4.36/platform.html#rescaleOnRuntimePreference)

The image is created via following code:

if (cachedElement == null) {
  String imageKey = ISharedImages.IMG_OBJ_ELEMENT;
  cachedElement = workbench.getSharedImages().getImage(imageKey);
}
ImageData imageData = (ImageData) cachedElement.getImageData().clone();
cachedElement = new Image(Display.getCurrent(), imageData);

It looks like that data is lost when calling new Image(Display.getCurrent(), image.getImageData().clone()); when "Use monitor-specific UI scaling" is enabled.

Could you please help in fixing this issue?

Thanks a lot,
Tobias

Tested under this environment:

• OS & version: Windows 11 - DPIUtil#deviceZoom has value 200

Workarounds

1. Use the nearest algorithm to scale images by setting this JVM flag: -Dswt.autoScale.method=nearest. The results are not optimal but they are not blurry.

• Use auto-scale "nearest" by default in Windows #2910 #2051

2. Use the constructor that takes a source Image instead of the one that takes the ImageData.

...
cachedFolder = new Image(cachedFolder.getDevice(), cachedFolder, SWT.IMAGE_COPY);
return cachedFolder;

Community

• I understand reporting an issue to this OSS project does not mandate anyone to fix it. Other contributors may consider the issue, or not, at their own convenience. The most efficient way to get it fixed is that I fix it myself and contribute it back as a good quality patch to the project.

[HeikoKlare]

Thank you for the report! We will have a look at this.

[fedejeanne]

I am testing this and I can reproduce it in Windows 10 too. These details are missing in the bug description:

• The images are blurry only if they are first instantiated in a big monitor (e.g. 200%). If the workbench is started in a 100% monitor the images are not blurry
• Once the images are blurry, moving them to another monitor doesn't fix the issue.

I am testing with 2 monitors, one at 100% and one at 200%.

[fedejeanne]

I was able to pinpoint the issue: it's the anti-alias that makes the images blurry. I still don't know why is this causing a problem in this particular use-case but commenting out this line in org.eclipse.swt.internal.DPIUtil.autoScaleImageData(Device, ImageData, float) makes the issue go away:

eclipse.platform.swt/bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/internal/DPIUtil.java

Line 303 in 00c6aef

gc.setAntialias (SWT.ON);

Alternatively, one can use the nearest algorithm to scale images by setting this JVM flag: -Dswt.autoScale.method=nearest.

I'll add it as a workaround in the description and I will continue to dig deeper tomorrow.

[fedejeanne]

Since today should be the build for M2, I have a workaround in store just in case there is no proper fix in time: #2051

[merks]

@akurtakov FYI

Since we've been doing light-weight M* it's generally the build on Friday that is the build that's contributed. And, given all the infrastructure problems, e.g.,

https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/5892

we might well slip into the weekend and contribute a build from Sunday...

[fedejeanne]

@akurtakov FYI

Since we've been doing light-weight M* it's generally the build on Friday that is the build that's contributed. And, given all the infrastructure problems, e.g.,

https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/5892

we might well slip into the weekend and contribute a build from Sunday...

... the silver lining :-D

Thanks Ed!

[fedejeanne]

I just found out that the issue does not come from cloning the ImageData but from using the constructor with the ImageData i.e. even if you use the original data, images will be blurry.

Said in code:

private Image getImage(Object obj) {
	if (obj instanceof TreeParent) {
		if (cachedFolder == null) {
			String imageKey = ISharedImages.IMG_OBJ_FOLDER;
			cachedFolder = workbench.getSharedImages().getImage(imageKey);
		}

		// Don't use the constructor with ImageData, use the one with a source Image to copy from
		cachedFolder = new Image(cachedFolder.getDevice(), cachedFolder, SWT.IMAGE_COPY);
		return cachedFolder;
	}
	if (cachedElement == null) {
		String imageKey = ISharedImages.IMG_OBJ_ELEMENT;
		cachedElement = workbench.getSharedImages().getImage(imageKey);
	}
	ImageData sameImageData = (ImageData) cachedElement.getImageData()/*.clone()*/;
	
	// This constructor still produces a blurry image.
	cachedElement = new Image(Display.getCurrent(), sameImageData);
	
	return cachedElement;
}

And it looks like this:

[fedejeanne]

After analyzing the provided sample code more in detail, the issue is that the cachedElement and cachedFolder images are generated over and over and this leads to the scaling algorithm being applied several times.

There is probably something that could be done to support these kind of use cases but in the meantime, can you please tell us where does the snippet of code come from @tobiasmelcher ? Is it adapted from code in Platform or is it in your product?

In any case, the code should generated the "original" images only once and, if necessary, produce the "clone" images always based on the original image.

[akoch-yatta]

Btw. after understanding the root cause I tested this issue with #1996 and improves this behavior a lot.

[tobiasmelcher]

After analyzing the provided sample code more in detail, the issue is that the cachedElement and cachedFolder images are generated over and over and this leads to the scaling algorithm being applied several times.

There is probably something that could be done to support these kind of use cases but in the meantime, can you please tell us where does the snippet of code come from @tobiasmelcher ? Is it adapted from code in Platform or is it in your product?

In any case, the code should generated the "original" images only once and, if necessary, produce the "clone" images always based on the original image.

The code was used in our product ABAP Development Tools in Eclipse. I think we did clone the images by mistake. It was working fine before introduction of the "Monitor-specific UI scaling" feature. I already adapted our code so that the problem does no longer occur. Anyhow, I think that the eclipse behavior changed here in an incompatible way. new Image(Display.getCurrent(), imageData) behaves now different than before.

[fedejeanne]

The code was used in our product ABAP Development Tools in Eclipse.

Thank you for the info, @tobiasmelcher . Good to know that it's not code in Platform, this means that there is no need to adapt any more code.

Anyhow, I think that the eclipse behavior changed here in an incompatible way. new Image(Display.getCurrent(), imageData) behaves now different than before.

Agreed, the behavior changed. Thank you for reporting it!