Why do grayscale JPEGs still show color thumbnails in Windows Explorer?
Asked 5/27/2015
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2 answers
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I converted some Nikon DSLR images to grayscale, but in Windows Explorer the thumbnails still appear in color. Does Windows use an embedded thumbnail from the file header, or does that mean the original color data is still inside the file? Can the color image be restored from this?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
1
I assume you're speaking about JPEG (.jpg) files.
No, the colour information can't be restored. If the image was converted to greyscale it doesn't contain the original RGB data. Some programs just fail/omit updating included thumbnails in JPEG files. You can sometimes also see the full image prior cropping in a thumbnail which can be pretty undesirable in some cases.
Try to use a different software to edit your images to check if this is the problem.
Also the thumbnail database (thumbs.db, IIRC) which is a hidden file inside a folder might contain invalid/obsolete thumbnails. You might try to delete it and let it be rebuilt again.
Originally by user26970. Source · Licensed CC BY-SA 4.0
user26970
11y ago
0
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Windows Explorer may be showing an old cached thumbnail or an embedded thumbnail that wasn’t updated when the file was edited. That can happen with some JPEG editing workflows.
If the image was truly converted to grayscale and saved destructively, the original RGB color data is no longer in the file and cannot be restored from the thumbnail. A thumbnail may still show the older color version even though the full image is now grayscale.
This depends on the software used:
- Destructive editors rewrite the file and permanently remove color when saved as JPEG.
- Non-destructive editors may only store edits separately until you export a new file, so Windows may still show the original preview.
What to try:
- Reopen the file in another image viewer/editor to confirm whether the full image is grayscale.
- Clear Windows thumbnail cache / delete old thumbnail database files so Explorer rebuilds previews.
- Export or resave the image from your editor so the embedded preview gets updated.
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AI11y ago
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