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From "Gary Lucas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (IMAGING-95) Some tiff processing takes very long
Date Thu, 18 Oct 2012 17:00:06 GMT

    [ https://issues.apache.org/jira/browse/IMAGING-95?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13479142#comment-13479142
] 

Gary Lucas commented on IMAGING-95:
-----------------------------------

I'm not part of the Apache Commons Imaging project team, but I am interested in this issue...
 Few people would welcome a speed enhancement for TIFF images with more enthusiasm than I
:-)

I tried your patch with a couple of test files I have and didn't see much different in measured
processing time.  Unfortunately, I've got all sorts of security software running on my computer
and it makes for a noisy test environment, so I can't be sure.   So I have a couple of questions:

a) Are there specific TIFF formats where you've observed an improvement?
b) Have you tried running before-and-after tests using the ApacheImagingSpeedAndMemoryTest.java
application?

The ApacheImagingSpeedAndMemory.java class is in the Commons Imaging code distribution under
the path src\test\java\org\apache\commons\imaging\examples   There are detailed instructions
for using it in the comments inside the code.  It is designed to give reasonably unambiguous
timing information about how long it takes to load an image (it is coded for TIFF images,
but can be edited to process other formats).
                
> Some tiff processing takes very long
> ------------------------------------
>
>                 Key: IMAGING-95
>                 URL: https://issues.apache.org/jira/browse/IMAGING-95
>             Project: Commons Imaging
>          Issue Type: Bug
>          Components: Format: TIFF
>    Affects Versions: 1.0
>            Reporter: Amit Gupta
>         Attachments: tiff_perf_fix2.patch
>
>
> org.apache.commons.imaging.formats.tiff.TiffReader.getTiffRawImageData(ByteSource, TiffDirectory)
226635	1
> org.apache.commons.imaging.common.bytesource.ByteSourceInputStream.getBlock(int, int)
226588	5616
> org.apache.commons.imaging.common.BinaryFileFunctions.skipBytes(InputStream, int)	226526
5616
> org.apache.commons.imaging.common.BinaryFileFunctions.skipBytes(InputStream, int, String)
226526	5616
> org.apache.commons.imaging.common.bytesource.ByteSourceInputStream$CacheReadingInputStream.read(byte[],
int, int)	226526	188656860
> org.apache.commons.imaging.common.bytesource.ByteSourceInputStream$CacheBlock.getNext()
64581	188651244
> skip bytes is being called repeatedly again and again, last column is invocation count
in one call tree. Second column is total number of time taken by that method in that call
tree..
> and skip method is not overridden org.apache.commons.imaging.common.bytesource.ByteSourceInputStream.CacheReadingInputStream
and default implementation of InputStream tries to use read method (which is overridden in
CacheReadingInputStream) to skip. 
> In case of a tiff, which has large number of strips, skip is repeatedly called and use
of read is inefficient as it tried to do a System.arraycopy. array copy is not needed in case
of skip operation, as the bytes were already read in block/cached, we can simply jump the
pointer (block by block)

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