"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...