https://bugs.kde.org/show_bug.cgi?id=420013
Bug ID: 420013
Summary: Blur Filters create artifacts that are revealed by
splitting the alpha out
Product: krita
Version: nightly build (please specify the git hash!)
Platform: Debian stable
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Filters
Assignee: krita-bugs-n...@kde.org
Reporter: ahab.greybe...@hotmail.co.uk
Target Milestone: ---
Created attachment 127487
--> https://bugs.kde.org/attachment.cgi?id=127487&action=edit
Example image of artifacts
SUMMARY
This happens for versions 4.2.0 onwards but does not happen in version 4.1.7.
If a simple painted shape has any blur filter applied then artifacts are
created in the RGB content and these can be revealed by splitting the alpha out
into a mask.
A .png file is attached (blur-artifacts-revealed.png) that shows an example.
Here is a .kra file with further examples for convenience of investigation:
https://www.dropbox.com/s/8ipsb35hsrgeet7/Sample-Blur-Artifacts.kra?dl=1
This was made using the 5.0.0 pre-alpha appimage 08-Apr git 78d1d45
STEPS TO REPRODUCE
1. On a new paint layer, paint a simple shape then apply any blur filter.
2. Do Layer - Split - Split Alpha Into Mask on that layer
3. Turn off the mask to reveal the artifacts.
4. Note that trying this with a filled rectangle of any size or aspect ratio
does not give artifacts.
5. Note the 'tile' structure of the artifacts and that this is not 512 x 512
and seems to vary in size.
6. Note that varying the type of blur filter or the parameters of the blur
filter does not make significant changes to the nature of the artifacts.
7. Having revealed the artifacts by alpha splitting, flatten the layer to
combine the alpha with the image then reapply a split alpha into mask.
Note that the artifacts are now gone. (Rendered away by the flattening?).
8. After the blur filter is applied to a layer, turn off the background layer
and export the layer as a .png with alpha preserved. Then open that .png file
and split the alpha out to a mask.
Note that there are no artifacts.
OBSERVED RESULT
See Steps To reproduce
EXPECTED RESULT
No artifacts
SOFTWARE/OS VERSIONS
Krita
Version: 5.0.0-prealpha (git 78d1d45)
Languages: en_GB, en, en, en_GB, en
Hidpi: true
Qt
Version (compiled): 5.12.7
Version (loaded): 5.12.7
OS Information
Build ABI: x86_64-little_endian-lp64
Build CPU: x86_64
CPU: x86_64
Kernel Type: linux
Kernel Version: 4.19.0-8-amd64
Pretty Productname: Debian GNU/Linux 10 (buster)
Product Type: debian
Product Version: 10
Desktop: MATE
OpenGL Info
Vendor: "NVIDIA Corporation"
Renderer: "GeForce GTX 750 Ti/PCIe/SSE2"
Version: "4.6.0 NVIDIA 418.74"
Shading language: "4.60 NVIDIA"
Requested format: QSurfaceFormat(version 3.0, options
QFlags<QSurfaceFormat::FormatOption>(DeprecatedFunctions), depthBufferSize 24,
redBufferSize 8, greenBufferSize 8, blueBufferSize 8, alphaBufferSize 8,
stencilBufferSize 8, samples -1, swapBehavior QSurfaceFormat::DoubleBuffer,
swapInterval 0, colorSpace QSurfaceFormat::DefaultColorSpace, profile
QSurfaceFormat::CompatibilityProfile)
Current format: QSurfaceFormat(version 4.6, options
QFlags<QSurfaceFormat::FormatOption>(DeprecatedFunctions), depthBufferSize 24,
redBufferSize 8, greenBufferSize 8, blueBufferSize 8, alphaBufferSize 8,
stencilBufferSize 8, samples -1, swapBehavior QSurfaceFormat::DoubleBuffer,
swapInterval 0, colorSpace QSurfaceFormat::DefaultColorSpace, profile
QSurfaceFormat::CompatibilityProfile)
Version: 4.6
Supports deprecated functions true
is OpenGL ES: false
QPA OpenGL Detection Info
supportsDesktopGL: true
supportsOpenGLES: true
isQtPreferOpenGLES: false
Hardware Information
GPU Acceleration: auto
Memory: 16039 Mb
Number of Cores: 8
Swap Location: /tmp
Current Settings
Current Swap Location: /tmp
Current Swap Location writable: true
Undo Enabled: true
Undo Stack Limit: 18
Use OpenGL: true
Use OpenGL Texture Buffer: true
Use AMD Vectorization Workaround: false
Canvas State: OPENGL_SUCCESS
Autosave Interval: 60
Use Backup Files: true
Number of Backups Kept: 1
Backup File Suffix: ~
Backup Location: Same Folder as the File
Backup Location writable: false
Use Win8 Pointer Input: false
Use RightMiddleTabletButton Workaround: false
Levels of Detail Enabled: false
Use Zip64: false
Display Information
Number of screens: 2
Screen: 0
Name: DVI-D-1
Depth: 24
Scale: 1
Resolution in pixels: 1280x1024
Manufacturer: Dell Inc.
Model: DELL 1704FPV-
Refresh Rate: 60
Screen: 1
Name: DVI-D-0
Depth: 24
Scale: 1
Resolution in pixels: 1280x1024
Manufacturer: Dell Inc.
Model: DELL 1704FPV-
Refresh Rate: 75
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