Last modified: 2012-04-04 00:36:49 UTC

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Bug 35684 - Black streaks across .jpeg images


Summary:	Black streaks across .jpeg images

Status:	RESOLVED DUPLICATE of bug 24854

Product:	MediaWiki
Classification:	Unclassified
Component:	File management (Other open bugs)
Version:	unspecified
Hardware:	All All

Importance:	Unprioritized normal (vote)
Target Milestone:	---
Assigned To:	Nobody - You can work on this!

URL:
Whiteboard:
Keywords:

Depends on:
Blocks:
	Show dependency tree / graph

Reported:	2012-04-03 23:55 UTC by Smallman
Modified:	2012-04-04 00:36 UTC (History)
CC List:	2 users (show)

See Also:
Web browser:	---
Mobile Platform:	---
Assignee Huggle Beta Tester:	---

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Description Smallman 2012-04-03 23:55:13 UTC

Several of the images in the following commons cat have black streaks across portions of the thumbs. 
http://commons.wikimedia.org/wiki/Category:Solar_Dynamics_Observatory

Sample thumbs include:

https://upload.wikimedia.org/wikipedia/commons/thumb/c/cc/417176main_SDO_Guide_CMR_Page_12_Image_0002.jpg/120px-417176main_SDO_Guide_CMR_Page_12_Image_0002.jpg

https://upload.wikimedia.org/wikipedia/commons/thumb/e/ef/417176main_SDO_Guide_CMR_Page_13_Image_0003.jpg/56px-417176main_SDO_Guide_CMR_Page_13_Image_0003.jpg

https://upload.wikimedia.org/wikipedia/commons/thumb/f/fd/417176main_SDO_Guide_CMR_Page_27_Image_0002.jpg/120px-417176main_SDO_Guide_CMR_Page_27_Image_0002.jpg

I've archived a the category at:
http://www.webcitation.org/66exsAOAx

This may be related to this bug:
https://bugzilla.wikimedia.org/show_bug.cgi?id=24854

Comment 1 Bawolff (Brian Wolff) 2012-04-04 00:36:49 UTC

For the first image listed:
bawolff@Bawolff-L:~$ exiftool 417176main_SDO_Guide_CMR_Page_12_Image_0002.jpg 
ExifTool Version Number         : 7.30
File Name                       : 417176main_SDO_Guide_CMR_Page_12_Image_0002.jpg
Directory                       : .
File Size                       : 175 kB
File Modification Date/Time     : 2010:02:12 22:50:40
File Type                       : JPEG
MIME Type                       : image/jpeg
JFIF Version                    : 1.1
Resolution Unit                 : inches
X Resolution                    : 150
Y Resolution                    : 150
DCT Encode Version              : 100
APP14 Flags 0                   : Encoded with Blend=1 downsampling
APP14 Flags 1                   : (none)
Color Transform                 : YCCK
Image Width                     : 579
Image Height                    : 579
Encoding Process                : Baseline DCT, Huffman coding
Bits Per Sample                 : 8
Color Components                : 4
Image Size                      : 579x579

The line of interest is:
>Color Transform                 : YCCK

So apparently its using a non-standard colour transform. Googling YCCK says:

"YCCK model is specific for the JPEG image compression. It is a variant of the YCbCr model containing an additional K channel (black). The fact is that JPEG codec performs more effectively if the luminance and color information are decoupled. Therefore, a CMYK image should be converted to YCCK before JPEG compression."

Hence this appears basically the same issue as bug 24854 (Non-standard colour models don't work well). Duping to that bug

*** This bug has been marked as a duplicate of bug 24854 ***

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