Maps, text and icons are "blurred" in Windows 10 version (1.19.0) - Resolution problem?

[Dret42]

Maps, text and icons are "blurred" in Windows 10

Maps, text and icons are "blurred" in Windows 10 version (1.19.0) - Resolution problem?

The problem is more evident on .IMG vecotr map format.

What have you done to circle down the problem?

I tryed to find some setting about QMapShack resolution but with no luck.

To Reproduce

Install on Window 10 and compare to 1.17.0 version

Expected behavior

Map should be not "blurred"

Screenshots

Here two screenshots (form both version) to compare.

Map used is in Garmin .IMG format downloaded form https://www.wanderreitkarte.de/index.php?lang=en
(but problem is visible in all .IMG format maps)

1.17

1.19 (blurred)

Attachments

Tracebacks

Desktop

• OS: Windows 10
• QMapShack Version: 1.19.0
• Window Manager: -

Additional context

[kiozen]

🤔 there has been no change in the code rendering Garmin maps. At least non that has any effect on rendering.

The only big change is switching from Qt5 to Qt6. That could have some fallout.

[JFritzle]

I don't know if this is the reason for blur in your maps, but map projection between QMS 1.17.x- and QMS 1.18.x+ has changed.

Open View -> Setup Map View . In Projection & Datum window hit Grid symbol button at upper right corner and select World Mercator (OSM) for projection. Result will be EPSG:3857. That solved at least blur issue in OSM based maps after moving to QMS 1.18.x+.

[Dret42]

Open View -> Setup Map View . In Projection & Datum window hit Grid symbol button at upper right corner and select World Mercator (OSM) for projection. Result will be EPSG:3857. That solved at least blur issue in OSM based maps after moving to QMS 1.18.x+.

Unfortunately it is already in EPGS:3857 :(

Even changing to UTM the situation does not change!

Any other Idea?

[Dret42]

Maybe I found a possible issue...

One years ago I got a similar problem on some maps into QGIS.
I that case the situation was generated by the default resolution of Windows on my Lenovo laptop that is 125% and not 100%.
This kind of settings is very common in many laptop Windows evironment..

In that case the QGIS developer added a function to adjust map resolution based also on this king of setting.

Unfortunatly is not possible to turn resolution at 100% because all other app (and SO too!) would broke!!!

I hope this could be an idea for a fix!

Thanks in advance!

[JFritzle]

My QMS 1.19.0 tests:
All screenshots are taken from whole 1920x1200 display.
QMS is always displayed using same width x height.
For size comparison, Windows console is shown above QMS window.

Screenshot 1:
Display scale 100% -> QMS map area without blur

Screenshot 2:
Display scale 125% -> QMS map area with blur

Screenshot 3:
Display scale 125% and QMS downscaled to 80% (1.25 x 0.8 = 1.0) -> QMS map area without blur

Total QMS application can get scaled by environment variable QT_SCALE_FACTOR.
First run Windows console command set QT_SCALE_FACTOR=0.80, then run QMS from same console and downscale QMS to 80%.
Both commands can get embedded into a .bat file.

Usable as workaround?

[Dret42]

Thanks!

I used this code (generated by ChatGPT! Sorry but I'm not familiar with .bat code!):

@echo off

set "OLD_QT_SCALE=%QT_SCALE_FACTOR%"


set "QT_SCALE_FACTOR=0.80"
start "" /D "your-path-to-qmpashack\QMapShack-1.19.0.0_Portable" "your-path-to-qmpashack\qmapshack.exe"


if defined OLD_QT_SCALE (
    set "QT_SCALE_FACTOR=%OLD_QT_SCALE%"
) else (
    set "QT_SCALE_FACTOR="
)

Now the blur effect has been fixed but (obviously) the entire UI has been scaled down!

I hope for a more robust solution in the future!

Thanks again!

[JFritzle]

@kiozen
The only big change is switching from Qt5 to Qt6. That could have some fallout.

Seems to be the culprit. This discussion handles exactly same blurry image issue with display scale 125% after transition from Qt5 to Qt6. As I understand discussion, Qt5 did some automatism which Qt6 after implementing high DPI functionality does not do anymore.

Reading discussion, I tried to prevent at least TMS maps from blur by some quick and especially dirty modifications of file CMapTMS.cpp:

Inserted lines

QScreen* screen = qApp->primaryScreen();
qreal devicePixelRatio = screen->devicePixelRatio();
buf.image.setDevicePixelRatio(devicePixelRatio);

before line
QPainter p(&buf.image);

Inserted line
img.setDevicePixelRatio(devicePixelRatio);
after line
diskCache->restore(url, img);

After modification

• there is no visible impact for display scale 100% , image ultra sharp and no blur, as devicePixelRatio is equal to 1.
• output looks like this for display scale 125% devicePixelRatio is equal to 1.25:
  
  -> Image ultra sharp and no blur. But tiles do not join together.
  Without modifications tiles join together but show blurry.

Perhaps this could be an approach to solve display scale issue?
Unfortunately, I am not able to find further necessary modification to make tiles fit together.
Adjustments to the scale and all items on map (waypoints, tracks, ...) are also likely.
@kiozen: Any idea how to continue?

[kiozen]

You might want to play with the IDrawContext::scale variable. But I can't tell if that really helps. I would need to dive deep into that stuff. Haven't done anything for ages with the complete scaling and drawing. Not sure if I find time the next days to have a closer look.

[JFritzle]

@Dret42

While trying to solve issue in QMS code (and not being sure if I will succeed) you could use a better workaround than setting environment variable QT_SCALE_FACTOR:

Instead, set environment variable QT_ENABLE_HIGHDPI_SCALING to value 0 to disable high-dpi scaling; effectively reverting to Qt 5 default behavior.

[JFritzle]

Following screenshots from Freizeitkarte Luxemburg and using same QMS settings are taken on a 125% scaled display.

Screenshot 1 - QMS 1.19.0 unmodified, environment variable QT_ENABLE_HIGHDPI_SCALING set to 0 -> sharp

Screenshot 2 - QMS 1.19.0 unmodified, environment variable QT_ENABLE_HIGHDPI_SCALING unset -> blurry

Screenshot 3 - QMS 1.19.0 modified, environment variable QT_ENABLE_HIGHDPI_SCALING unset -> sharp

Modified function IDrawContext::resize in file src/qmapshack/canvas/IDrawContext.cpp
from

  ...
  center = QPointF(viewWidth / 2.0, viewHeight / 2.0);
  bufWidth = viewWidth + 2 * BUFFER_BORDER;
  bufHeight = viewHeight + 2 * BUFFER_BORDER;

  buffer[0].image = QImage(bufWidth, bufHeight, QImage::Format_ARGB32);
  buffer[0].image.fill(Qt::transparent);

  buffer[1].image = QImage(bufWidth, bufHeight, QImage::Format_ARGB32);
  buffer[1].image.fill(Qt::transparent);
  ...

to

  ...
  center = QPointF(viewWidth / 2.0, viewHeight / 2.0);
  bufWidth = viewWidth + 2 * BUFFER_BORDER;
  bufHeight = viewHeight + 2 * BUFFER_BORDER;

  QScreen* screen = qApp->primaryScreen();
  qreal devicePixelRatio = screen->devicePixelRatio();

  bufWidth *= devicePixelRatio * devicePixelRatio;
  bufHeight *= devicePixelRatio * devicePixelRatio;

  buffer[0].image = QImage(bufWidth, bufHeight, QImage::Format_ARGB32);
  buffer[0].image.fill(Qt::transparent);
  buffer[0].image.setDevicePixelRatio(devicePixelRatio);

  buffer[1].image = QImage(bufWidth, bufHeight, QImage::Format_ARGB32);
  buffer[1].image.fill(Qt::transparent);
  buffer[1].image.setDevicePixelRatio(devicePixelRatio);
  ...

Don't ask why bufwidth and bufheight have to by multiplied by devicePixelRatio * devicePixelRatio.
But without, map image does not cover entire canvas window.

The only map types I have for testing are TMS, WMTS and IMG maps. While modification solves blur effect with IMG files, unfortunatley TMS and WMTS files still are blurry, presumably because these are tile based. Tile images become sharp too, when setDevicePixelRatio(devicePixelRatio) applied to image. But then tiles are smaller and there are gaps between tiles. Presumably algorithm to map tiles into canvas in files CMapTMS.cpp etc. has to be modified to fill more tiles at condensed positions. I am afraid this is beyond my skills.

[kiozen]

Maybe a few hints that might help:

• The buffer (size of QImage) covers the visible canvas with an overlap of 50 pixel at each border. This should not be altered.
• IDrawContext::run() is the thread that actually draws into the buffer. The area to cover is defined by ref1..4

Therefore the goal is to translate the information covered by the ref1..4 into the pixels of the buffer. Regardless of what kind of map or DEM. I doubt we have to alter the map specific code, because if we have to, we break that fundamental concept.

I still do not understand how the OS scaling affects the canvas. I would expect that the QT framework to tell the canvas to have a smaller size in pixels than it has on the screen. And as the complete window of the app is scaled up it fits. However I do not understand why drawing a "smaller" map results into an up-scaled image without blur. Is this really like that? Or is it just an illusion?

Imho the only reasonable way would be to except the canvas area from scaling and get the real size in pixels for it. But I do not see how this should be implemented in Qt.

As said I am not really into that subject. Therefore I might be wrong.

[JFritzle]

What I have achieved so far, regardless of QMS screen's display scale:

• all map types (IMG, TMS, WMTS, DEM, ...) are displayed without blur
• tile-based maps (TMS, WMTS, DEM, ...) join together seamlessly
• maps occupy whole QMS map pixel area from edge to edge, regardless of zoom level
• for each zoom level, same coordinate range of different map types is mapped to identical QMS map pixels on screen
• already existing GIS elements (tracks, routes waypoints, ...) fit to their position on map
• when moving QMS toplevel windows between displays of different display scale, for example one monitor is 125% and the other is 100%, maps are redrawn without blur according to display scale

What is still open:

• Translation of mouse picks from screen coordinates to device-independend coordinates is not yet ready
  Therefore newly created GIS elements do not fit: too large, with offset
• Map overlays (highlights, ..) do not fit
• ???

[kiozen]

If you want you can push to a branch in your repo and I can test, check and review a bit if time permits