Author: M8R-udfkkf
Description:
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:
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
Version: unspecified
Severity: normal
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