# Segment editor effect sourceVolumeImageData not updated
**URL:** https://discourse.slicer.org/t/segment-editor-effect-sourcevolumeimagedata-not-updated/37500
**Category:** Development
**Tags:** segment-editor
**Created:** [July 22, 2024, 1:59pm UTC](https://discourse.slicer.org/t/segment-editor-effect-sourcevolumeimagedata-not-updated/37500 "2024-07-22T13:59:11Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Llujoo](https://discourse.slicer.org/u/Llujoo)
#### Post date: [July 22, 2024, 1:59pm UTC](https://discourse.slicer.org/t/segment-editor-effect-sourcevolumeimagedata-not-updated/37500/1 "2024-07-22T13:59:11Z")
Hello I am writing a SegmentEditorEffect based on AbstractScriptedSegmentEditorEffect.
When I call `self.scriptedEffect.sourceVolumeImageData()` everything works fine. However if I change the selected source volume in the segment editor the change will not be recognized and once I call `self.scriptedEffect.sourceVolumeImageData()` again, I get the old image data.
If I change the segmentation this is reset and I will get the first selected volume but cannot get any follow up selection
Is there a way to force an update of this?
---
### Author:  [@lassoan](https://discourse.slicer.org/u/lassoan)
#### Post date: [July 22, 2024, 3:57pm UTC](https://discourse.slicer.org/t/segment-editor-effect-sourcevolumeimagedata-not-updated/37500/2 "2024-07-22T15:57:23Z")
It all works well for me. For example, load two volumes, use threshold effect, select another source volume, use threshold effect.
Please provide full script that I can simply copy-paste into the Python console and reproduces the behavior you reported.
---
### Author:  [@Llujoo](https://discourse.slicer.org/u/Llujoo)
#### Post date: [July 23, 2024, 7:17am UTC](https://discourse.slicer.org/t/segment-editor-effect-sourcevolumeimagedata-not-updated/37500/3 "2024-07-23T07:17:47Z")
Thanks for your quick reply, Andras.
I tried ThresholdEffect’s and it works fine here. I don’t know why though. When I copy code and add a check to see if the sourceVolume has changed it has the same behavior.
I am pretty new to slicer and python so I might be making obvious mistakes.
I’ve tried to create a minimal version:
1. Save this to MySegmentEditorEffect.py
2. Run the lines below after fixing the path.
3. Drag and drop at least 2 images
4. Switch the images in Segment Editor’s ComboBox.
5. In my opinion you shoulg get the “sourceImageData changed”-Message every time you change the image
```auto
from SegmentEditorEffects import *
class MySegmentEditorEffect(AbstractScriptedSegmentEditorEffect):
def __init__ (self, scriptedEffect):
AbstractScriptedSegmentEditorEffect. __init__ (self, scriptedEffect)
scriptedEffect.name = "MySegmentEditorEffect"
self.sourceImageData = None
def clone(self):
# It should not be necessary to modify this method
import qSlicerSegmentationsEditorEffectsPythonQt as effects
clonedEffect = effects.qSlicerSegmentEditorScriptedEffect(None)
clonedEffect.setPythonSource( __file__.replace('\\','/'))
return clonedEffect
def sourceVolumeNodeChanged(self):
sourceImageData = self.scriptedEffect.sourceVolumeImageData()
if(self.sourceImageData != sourceImageData):
if( sourceImageData is None):
print(f"sourceImageData changed: None")
else:
print(f"sourceImageData changed: {sourceImageData.GetExtent()}")
self.sourceImageData = sourceImageData
```
```auto
import qSlicerSegmentationsEditorEffectsPythonQt as effects
scriptedEffect = effects.qSlicerSegmentEditorScriptedEffect(None)
scriptedEffect.setPythonSource(r"Your_Location\MySegmentEditorEffect.py")
scriptedEffect.self().register()
```
---
### Author:  [@Llujoo](https://discourse.slicer.org/u/Llujoo)
#### Post date: [July 25, 2024, 12:38pm UTC](https://discourse.slicer.org/t/segment-editor-effect-sourcevolumeimagedata-not-updated/37500/4 "2024-07-25T12:38:15Z")
I’ve investigated further and while the SegmentEditorThresholdEffect works as it should it has the same issue. If i change up the sourceVolumeNodeChanged method as below, I get the same behavior.
Maybe I will find out where it get’s the correct data but this seems like a genuine bug to me.
Have you found anything @lassoan ?
```auto
def sourceVolumeNodeChanged(self):
# Set scalar range of source volume image data to threshold slider
masterImageData = self.scriptedEffect.sourceVolumeImageData()
if masterImageData:
print(f"this should change: {masterImageData.GetDimensions()}")
lo, hi = masterImageData.GetScalarRange()
self.thresholdSlider.setRange(lo, hi)
self.thresholdSlider.singleStep = (hi - lo) / 1000.
if (self.scriptedEffect.doubleParameter("MinimumThreshold") == self.scriptedEffect.doubleParameter("MaximumThreshold")):
# has not been initialized yet
self.scriptedEffect.setParameter("MinimumThreshold", lo + (hi - lo) * 0.25)
self.scriptedEffect.setParameter("MaximumThreshold", hi)
```
---
### Author:  [@Llujoo](https://discourse.slicer.org/u/Llujoo)
#### Post date: [July 25, 2024, 12:46pm UTC](https://discourse.slicer.org/t/segment-editor-effect-sourcevolumeimagedata-not-updated/37500/5 "2024-07-25T12:46:44Z")
Okay I found a solution. I can get the Node instead and then the image data. The node is updated.
```auto
sourceImageData = self.scriptedEffect.parameterSetNode().GetSourceVolumeNode().GetImageData()
```
---
### Author:  [@lassoan](https://discourse.slicer.org/u/lassoan)
#### Post date: [July 25, 2024, 3:57pm UTC](https://discourse.slicer.org/t/segment-editor-effect-sourcevolumeimagedata-not-updated/37500/6 "2024-07-25T15:57:16Z")
This code gives you the source volume’s image data as is:
```auto
self.scriptedEffect.parameterSetNode().GetSourceVolumeNode().GetImageData()
```
This is usually not what you need, because the source volume’s geometry (origin, spacing, axis directions, extents) may differ from the segmentation’s.
This gives you the image data resampled to the segmentation’s geometry (taking into account all parent transforms, including warping transforms):
```auto
masterImageData = self.scriptedEffect.sourceVolumeImageData()
```
What you observed (image data is resampled to the segmentation’s geometry, therefore dimension does not change) maybe unexpected, but it is the correct, intended behavior.