FreeImage / Support Requests / #36 FreeImage decodes JPEG wrong?

#36 FreeImage decodes JPEG wrong?

Milestone: None

Status: pending

Owner: Hervé Drolon

Labels: jpeg (1)

Priority: 5

Updated: 2015-04-28

Created: 2015-04-26

Creator: Ocirne94

Private: No

It looks like FreeImage (3.15.4, Ubuntu) decodes JPEG images differently from most other software: for example the attached image is
(0 0 2) (255 255 0)
(255 1 255) (254 254 252)
according to the GIMP, gwenview, and even FreeImage's PNG decoder.

But FreeImage decodes the JPEG as

(0 1 0) (250 250 0)
(252 0 249) (249 250 245)

Please help!
Ocirne

1 Attachments

z.jpg

Discussion

Hervé Drolon - 2015-04-28

Hi,

With the FreeImage release 3.13.0 (sept 2009), FreeImage was updated from LibJPEG 6b to LibJPEG 7.
In Release 3.17.0, FreeImage now use LibJPEG 9a. The compression / decompression algorithm is a little different from the original LibJPEG 6b one.
Somewhere between 6b and 8, IJG did a significant rewrite to their library for applying chrominance. The result is that JPEGs rendered by IJG's jpeglib v.8 (or later) no longer look like JPEGs rendered with other libraries using LibJPEG 6b.

Hope this help,

Hervé

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Hervé Drolon - 2015-04-28

status: open --> pending

assigned_to: Hervé Drolon

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#36 FreeImage decodes JPEG wrong?

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