Layer transparence in tif format fails

[qgib]

Author Name: Gerhard Spieles (Gerhard Spieles)
Original Redmine Issue: 1278

Redmine category:rasters
Assignee: ersts -

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geo-referenced tif images appears black when change transparence in layer properity.

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• qgis_transparenz_tif.pdf (Gerhard Spieles)
• b_plan_fell_kortsfuhr.tfw (Gerhard Spieles)
• b_plan_klostergarten-geo.tfw (Gerhard Spieles)

[qgib]

Author Name: Maciej Sieczka - (Maciej Sieczka -)

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Can you attach a small example?

[qgib]

Author Name: ersts - (ersts -)

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Hi gespiel! Sorry you are having problems.

geo-referenced tif images appears black when change transparence in layer properity.

To me the uniformly gray display, as shown in the PDF example, makes me think you need to apply an enhance or "stretch" to the image.

1. Does your tif look correct outside of QGIS?
2. When the transparency is 0% does your image look correct/as you expect?
3. How was your tif georeferenced? Did you use the QGIS plugin? (if yes, can you explain the setting you used)

Is it possible to post a copy of your tif?

[qgib]

Author Name: Gerhard Spieles (Gerhard Spieles)

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Hi,
outside Qgis, the tif-iamges look ok.
Attached are two tif images. Adding raster Layer without change trasparency, both images look ok in Qgis. Change transparence of the image b_plan_fell_kortsfuhr.tif is ok.
change tranparence in the rasterlayer of image b_plan_klostergarten-geo.tif, the image get grey, change agains to transparence 0%, the image get black.

[qgib]

Author Name: Gerhard Spieles (Gerhard Spieles)

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Sorry,
tif images are zip-compressed near 600 kB, so upload is not possible.
Can you tell me email ontact.

[qgib]

Author Name: ersts - (ersts -)

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you can send them to ersts

at amnh.org

[qgib]

Author Name: ersts - (ersts -)

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Can we get a confirmation that this is still a problem in the Version 1.0.0 release?

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• status_id was changed from Open to In Progress

[qgib]

Author Name: Gerhard Spieles (Gerhard Spieles)

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Hello Ersts,

thank for looking to the problem.
In Qgis 1.0, preview II, the problem is nearly solved. In "one Band color tifs", transparency of the white colour is shown in gray.
You can solve this by looking to the color-table and add the colour 0.0 (white) and 1.0 (grey) to the tranparent pixel list.

I couldnt test it on version 1.0 stabble, because the MSVC based build of QGIS terminates with a dll-fault in Windows. (i have Qgis strictly isntalled to the wiki.qgis.org installation guide)

[qgib]

Author Name: ersts - (ersts -)

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Replying to [comment:8 gespiel]:

In "one Band color tifs", transparency of the white colour is shown in gray.

I am sorry but I don't understand. If you change the layer's transparency, all colors will change. Is there a dark layer under the white region?

You can solve this by looking to the color-table and add the colour 0.0 (white) and 1.0 (grey) to the tranparent pixel list.

How many pixel values do you have? Is it just that you don't want 0 and 1 to be shaded?

[qgib]

Author Name: Paolo Cavallini (@pcav)

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Please gespiel, could you test again with 1.0.1? I cannot reproduce your problem, so it might have been fixed. If so, please close it.

[qgib]

Author Name: Paolo Cavallini (@pcav)

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According to our new bug policy, I'm closing this, pending feedback from the user. In case it is still valid, please reopen it. Sorry for the additional trouble.

[qgib]

Author Name: Paolo Cavallini (@pcav)

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• resolution was changed from to invalid
• status_id was changed from In Progress to Closed