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Exif TAG_THUMBNAIL_OFFSET reports wrong value #578

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StefanOltmann opened this issue Jun 2, 2022 · 1 comment · Fixed by #612
Closed

Exif TAG_THUMBNAIL_OFFSET reports wrong value #578

StefanOltmann opened this issue Jun 2, 2022 · 1 comment · Fixed by #612
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format-exif format-jpeg help wanted image-queue Actionable issue with sample image

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@StefanOltmann
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I try to extract a thumbnail from a JPG, but exifThumbnail.getInt(ExifThumbnailDirectory.TAG_THUMBNAIL_OFFSET) reports the wrong offset compared to exiftool, which has the correct value.

I tried this on multiple Unsplash photos like this one:
FFsiikfJEAI

I'm certain the logic determining the thumbnail offset is broken.
The thumbnail length is correct.
@StefanOltmann StefanOltmann changed the title TAG_THUMBNAIL_OFFSET reports wrong number TAG_THUMBNAIL_OFFSET reports wrong value Jun 2, 2022
@StefanOltmann StefanOltmann mentioned this issue Jun 2, 2022
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@drewnoakes drewnoakes added help wanted format-jpeg image-queue Actionable issue with sample image labels Jun 5, 2022
@drewnoakes drewnoakes changed the title TAG_THUMBNAIL_OFFSET reports wrong value Exif TAG_THUMBNAIL_OFFSET reports wrong value Jun 5, 2022
@StefanOltmann
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For anyone still looking: The library https://github.com/dragon66/pixymeta can report the correct thumbnail offsets and also extract the bytes.

drewnoakes added a commit that referenced this issue May 8, 2023
@drewnoakes
Fix Exif thumbnail offset
1e56363 
Fixes #578

The offset is currently reported relative to the start of the Exif data. However, most users will need the value relative to the start of the outermost data stream. This change attempts to provide that value.

Should work for JPEG and RAW files. Won't work for Exif data embedded within other formats such as PNG, QuickTime, WebP or HEIF. Such support could be added in future.
@drewnoakes drewnoakes mentioned this issue May 8, 2023
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drewnoakes added a commit that referenced this issue May 8, 2023
@drewnoakes
Fix Exif thumbnail offset
b4a2422 
Fixes #578

The offset is currently reported relative to the start of the Exif data. However, most users will need the value relative to the start of the outermost data stream. This change attempts to provide that value.

Should work for JPEG and RAW files. Won't work for Exif data embedded within other formats such as PNG, QuickTime, WebP or HEIF. Such support could be added in future.
@don-vip don-vip mentioned this issue Jul 20, 2024
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format-exif format-jpeg help wanted image-queue Actionable issue with sample image
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Fix Exif thumbnail offset drewnoakes/metadata-extractor
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@drewnoakes @StefanOltmann