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Thumbnails for specific TIFF pages have small rendering errors, ugly edges, glow missing
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Restricted Application added a subscriber: Aklapper. · View Herald TranscriptApr 16 2018, 5:40 PM
Aklapper renamed this task from TIFF scaling rendering error, ugly edges, glow missing to Thumbnails for specific TIFF pages have small rendering errors, ugly edges, glow missing.Apr 16 2018, 5:44 PM
Restricted Application added a project: Multimedia. · View Herald TranscriptApr 16 2018, 5:44 PM

Thanks for clarifying the title Aklapper. I had found T47212 but I do not believe it is the same issue. That "bug" (it's more or less by design) is caused by sharpening not being applied to TIFF images. Applying sharpening to this TIFF won't resolve the issues described.

Is the TIF scaled down before the thumbnail is created? If so, the bug might be easily "fixable" as a workaround, by reversing the process: Generate the large JPG and scale that down. Because that seems to work nicely.

ToBeFree added a comment.EditedApr 16 2018, 7:12 PM

Oh, this is a very weird, possibly broken TIFF file. Opening it in GIMP looks very different again!

Note how black the right half is! Exporting this file as PNG creates this image:

Atmospheric glow missing!

(scaled down to 1000px for upload)


The real surprise came when I added a white layer above the original TIFF:

The TIFF file contains "TIFF channels", additionally to the RGB channels. Two of them:

(This is an animated GIF, click to play!)

I have never seen such an unusual file before. It should be replaced by a PNG, solving all problems.

This file comes straight from NASA. If you find any evidence of a fake moon landing in those channels let us know. ;-)

Converting it to PNG is something I wanted to do as well.. Except I had trouble opening the file as well. I'll ask someone else.

And how strange is this? https://upload.wikimedia.org/wikipedia/commons/thumb/4/49/Earth_Western_Hemisphere.tif/lossy-page1-2048px-Earth_Western_Hemisphere.tif.png

AlexisJazz added a comment.EditedApr 16 2018, 11:22 PM

I've converted the images:
https://commons.wikimedia.org/wiki/File:Earth_Eastern_Hemisphere_2002.png
https://commons.wikimedia.org/wiki/File:Earth_Western_Hemisphere_2002.png

I had to load the images in my PDF viewer, print them to a file, use the gimp and presto png?? I checked to be sure the conversion went well and they look just like the jpg files from NASA, minus the compression artifacts.

@ToBeFree : thanks for the help! I'm not sure if this bug should be fixed or not. It probably needs to be fixed in some library Wikimedia uses.