[
https://issues.apache.org/jira/browse/SANSELAN-56?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13120612#comment-13120612
]
Sebb commented on SANSELAN-56:
------------------------------
It's not policy to segregate documentation and code patches, however in this
case the doc patches are not directly related to the issue.
If you wish to provide Javadoc patches, please raise a separate JIRA for these.
Each patch should deal with a single issue, and should be the minimum needed to
solve the issue; any docs in the patch should relate only to the issue being
addressed.
Otherwise it makes reviewing the patch harder, and if the patch is applied with
spurious changes, it makes reviewing the commit message harder as well.
A single patch may be seen by lots of people, so any extra work trying to
understand it may be multiplied many times.
[This is getting rather off-topic for this issue; probably ought to be
documented elsewhere]
> proposed enhancement reduces load time for some image files by 40 percent
> -------------------------------------------------------------------------
>
> Key: SANSELAN-56
> URL: https://issues.apache.org/jira/browse/SANSELAN-56
> Project: Commons Sanselan
> Issue Type: Improvement
> Environment: Tested in Windows, Linux, MacOS
> Reporter: Gary Lucas
> Labels: api-change
> Attachments: Sanselan-56-SpeedEnhanceTiff.patch
>
> Original Estimate: 48h
> Remaining Estimate: 48h
>
> I have identified an enhancement that reduces the time required to load TIFF
> image by 40 percent. I have tested a modified version of Sanselan under
> Windows, Linux, and MacOS with consistent savings on each platform.
> Additionally, I suspect that this technique may be applicable to other areas
> of the Sanselan code base, including more popular image formats supported by
> Sanselan such as JPEG, PNG, etc.
> I propose to add the relevant code changes to the Sanselan code base. Once
> these modifications are in place, there would be an opportunity for others to
> look at the pro's and cons' of applying the techniques to other data formats.
> The Enhancement
> To load an image from a TIFF file, Sanselan performs extensive data
> processing in order to obtain RGB values for the pixels in the output image.
> The code for that processing appears to be well written and efficient. Once
> the RGB value are obtained, they are stored in a Java BufferedImage using a
> call to the setRGB() method.
> Unfortunately, setRGB() is an extremely inefficient method. A much, much
> better approach is to store the data into an integer array and defer the
> creation of the buffered image until all information for the image has been
> collected. Java has a nice (though somewhat obscure) API that lets memory
> in an integer array be transferred directly to a BufferedImage so that the
> system does not have to allocate additional memory for this procedure (a very
> nice feature when dealing with huge images). This change virtually
> eliminated the overhead for transferring data to images, which accounted for
> 40 percent of the time required to load images. For TIFF files, this was a
> reasonable approach because the TiffImageParser class always loads 4-byte
> image and the getGrayscaleBufferedImage() method is never used. I have not
> investigated the code for the other renders, but some refinement might be
> needed for the one-byte grayscale images.
> Steps to Integration
> In sanselan.common, a new class called ImagePrep was created. ImagePrep
> carries a width, height, and an integer array for storing pixels. It
> provides its own setRGB() method which looks just like the one in
> BufferedImage. Finally, it provides a method called getBufferedImage()
> which creates a BufferedImage from its internal the integer array when the
> processing is complete.
> In the TiffImageParser classes, data is read from input stream and
> transferred to pixel values in a series of classes known as
> PhotometricInterpreters. These were modified to operate on ImagePrep objects
> rather than BufferedImage objects. The DataReader and TiffImageParser
> classes were modified to pass ImagePrep objects into the photometric
> interpreters rather than using BufferedImages.
> At the very last step, before passing its result back to the calling method
> (the Sanselan main class, etc.), the TiffImageParser used the
> ImagePrep.getBufferedImage() to convert the result to the expected form.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
