[OpenJDK 2D-Dev] <OpenJDK 2D-Dev> Review request for JDK - 8041501 : ImageIO reader is not capable of reading JPEGs without JFIF header

[Phil Race]

Rather than adding a comment block, it seems you need to edit the 
preceding one.

  * IJG assumes all unidentified 3-channels are YCbCr.
1715                  * We assume that only if the second two channels are
1716                  * subsampled (either horizontally or vertically).  If not,
1717                  * we assume RGB.

The fix is invalidating that comment but that is intended since
(a) following the comment is causing the bug
(b) the comment is contradicting the public Metadata spec

For the benefit of others, the text in the spec is :
----
If neither marker segment is present, the following procedure is followed: ....
For 3- and 4-channel images, the component ids are consulted.  If these
values are 1-3 for a 3-channel image, then the image is assumed to be YCbCr.

... Otherwise, 3-channel subsampled images are assumed to be YCbCr,
3-channel non-subsampled images are assumed to be RGB
---

So here is my suggested replacement text for the existing comment block :
---
In the absence of certain markers, IJG has interpreted component id's of [1,2,3] as meaning YCbCr.
We follow that interpretation, which is additionally described in the Image I/O JPEG metadata spec.
If that condition is not met here the next step here is to examine the subsampling factors
If any differ we also assume YCbCr, but if all are the same then we assume RGB
This is also described in the Image I/O JPEG metadata spec.

--

-phil.

On 11/23/2015 04:01 AM, Jayathirth D V wrote:
>
> Hi Prasanta,
>
> Removed repeated usage of getWidth() and getHeight(). Please review.
>
> http://cr.openjdk.java.net/~jdv/8041501/webrev.02/ 
> <http://cr.openjdk.java.net/%7Ejdv/8041501/webrev.02/>
>
> Thanks,
>
> Jay
>
> *From:*prasanta sadhukhan
> *Sent:* Monday, November 23, 2015 5:15 PM
> *To:* Jayathirth D V
> *Cc:* Philip Race; 2d-dev at openjdk.java.net
> *Subject:* Re: <OpenJDK 2D-Dev> Review request for JDK - 8041501 : 
> ImageIO reader is not capable of reading JPEGs without JFIF header
>
> On 11/23/2015 5:11 PM, Jayathirth D V wrote:
>
>     Hi Prasanta,
>
>     Thanks for suggestion. I have made related changes and updated the
>     Webrev.
>
>     Webrev : http://cr.openjdk.java.net/~jdv/8041501/webrev.01/
>     <http://cr.openjdk.java.net/%7Ejdv/8041501/webrev.01/>
>
>     Please review.
>
> There's no point getting the width & height repeatedly . You can get 
> it once and use that info in the loop. It's not going to change in 
> runtime, isn;t it :-)
>
> Regards
> Prasanta
>
>     Thanks,
>
>     Jay
>
>     *From:*prasanta sadhukhan
>     *Sent:* Monday, November 23, 2015 4:43 PM
>     *To:* Jayathirth D V; 2d-dev at openjdk.java.net
>     <mailto:2d-dev at openjdk.java.net>
>     *Cc:* Philip Race
>     *Subject:* Re: <OpenJDK 2D-Dev> Review request for JDK - 8041501 :
>     ImageIO reader is not capable of reading JPEGs without JFIF header
>
>     Looks ok to me.
>     But probably you could check for image width &height
>     programmatically instead of hardcoding to 64 in testcode.
>
>     Regards
>     Prasanta
>
>     On 11/23/2015 4:09 PM, Jayathirth D V wrote:
>
>         Hello All,
>
>         _Please review following fix in JDK9:_
>
>         Bug : https://bugs.openjdk.java.net/browse/JDK-8041501
>
>         Webrev : http://cr.openjdk.java.net/~jdv/8041501/webrev.00/
>         <http://cr.openjdk.java.net/%7Ejdv/8041501/webrev.00/>
>
>         Issue : Pink discoloration when we read JPEG images without
>         JFIF & EXIF header and having no subsampling.
>
>         Root cause : We are overriding JPEG color space set in IJG
>         library at imageioJPEG.c without checking component ID's
>         properly when JFIF & EXIF are not there. Decision to change
>         color space is solely done consulting sampling factors.
>
>         Solution : Added extra check to verify component ID's also
>         before changing color space determined by IJG library when
>         there is no JFIF & EXIF header.
>
>         Thanks,
>
>         Jay
>

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