It looks like JPEG files have protection for scanning for an FF and
assuming it is a marker by making sure that all FF bytes that appear in
data are followed by a harmless byte, so a brute force search is
probably fine. But it still seems wasteful when we know we are at a tag
and we know the sizes of all of the tags, we should be able to skip
around the file looking for the SOI directly...
...jim
On 6/2/2016 5:10 AM, Jayathirth D V wrote:
Fixed typo.
*From:*Jayathirth D V
*Sent:* Thursday, June 02, 2016 5:08 PM
*To:* Philip Race
*Cc:* Jim Graham; 2d-dev@openjdk.java.net
*Subject:* RE: Review Request for JDK-8152672 : Exception while getting
second image properties for JPEG with embedded thumbnail
Hi Phil,
We have two kind of images with which we are able to reproduce the issue:
1) sample.jpg present in JBS bug(We can’t use this image because it
is licensed ).
2) JpegEmbedThumbnail.jpg taken using Prasanta’s camera and used in
webrev.
_ _
_sample.jpg : _
_ _
If we do getNumImages() it will return 2. getNumImages() follows the
same logic of skipping markers with length and registering SOI to get
number of images.
sample.jpg has markers as follows :
SOI -> APP1 - > SOI -> EOI -> APP1 End -> EOI -> SOI -> EOI
I have dumped first image its SOI is first one in the above list and for
second image it is third one in the list. getNumImages() counts first
and third SOI for number of images. But in case of skipImage() we are
getting inside APP1 marker and considering its SOI.
_JpegEmbedThumbnail.jpg :_
_ _
If we do getNumImages() it will return 1.
JpegEmbedThumbnail.jpg has markers as follows :
SOI -> APP1 -> SOI -> EOI -> APP1 End -> APP2 -> SOI -> APP2 End -> APP2
-> EOI -> APP2 End -> EOI
getNumImages() counts only first SOI for number of images. But in case
of skipImage() we will are getting inside APP1 and APP2 markers also.
Thanks,
Jay
*From:*Phil Race
*Sent:* Thursday, June 02, 2016 4:05 AM
*To:* Jayathirth D V
*Cc:* Jim Graham; 2d-dev@openjdk.java.net <mailto:2d-dev@openjdk.java.net>
*Subject:* Re: Review Request for JDK-8152672 : Exception while getting
second image properties for JPEG with embedded thumbnail
I am bit doubtful about this. Are you sure we are correct in reporting
two images to begin with ?
Thumbnails should not get counted ..
-phil.
On 06/01/2016 01:06 AM, Jayathirth D V wrote:
Updated bug title in JBS as it was misleading.
*From:* Jayathirth D V
*Sent:* Wednesday, June 01, 2016 12:48 PM
*To:* Philip Race; Jim Graham
*Cc:* 2d-dev@openjdk.java.net <mailto:2d-dev@openjdk.java.net>
*Subject:* Review Request for JDK-8152672 : Exception getting
thumbnail size for JPEG with embedded thumbnail
Hi,
_Please review the following fix in JDK9:_
Bug : https://bugs.openjdk.java.net/browse/JDK-8152672
Webrev : http://cr.openjdk.java.net/~jdv/8152672/webrev.00/
<http://cr.openjdk.java.net/%7Ejdv/8152672/webrev.00/>
Issue : When we are trying to get properties related to second image
in JPEG file we are getting IIOException mentioning that it is not a
JPEG file.
Root cause : When we are skipping first image to reach second image
header, we are just trying to find next available EOI marker. But if
first image has embedded thumbnail in APP1 marker, we will reach to
EOI of this thumbnail and not EOI of first image. So after we reach
EOI of embedded thumbnail we try to access second image SOI marker
which will fail.
Solution : We have to change the logic of how we skip to consecutive
images in JPEG file. We know that application markers, comments or
other markers can contain data same as SOI & EOI. Instead of just
checking for EOI marker serially, we should read length of these
markers and skip them.
Thanks,
Jay
