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From "Damjan Jovanovic (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (SANSELAN-75) Improve speed of TIFF Index-Color Palette
Date Fri, 27 Apr 2012 08:23:51 GMT

     [ https://issues.apache.org/jira/browse/SANSELAN-75?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Damjan Jovanovic resolved SANSELAN-75.
--------------------------------------

       Resolution: Fixed
    Fix Version/s: 1.0

Patch applied, resolving fixed.
Thank you for your contribution!

                
> Improve speed of TIFF Index-Color Palette 
> ------------------------------------------
>
>                 Key: SANSELAN-75
>                 URL: https://issues.apache.org/jira/browse/SANSELAN-75
>             Project: Commons Sanselan
>          Issue Type: Improvement
>          Components: Format: TIFF
>            Reporter: Gary Lucas
>             Fix For: 1.0
>
>         Attachments: IndexColorPalette.tif, Tracker_Item_75_23_Apr_2012.patch
>
>   Original Estimate: 0h
>  Remaining Estimate: 0h
>
> TIFF supports an 8-bit-per-pixel, "indexed color" model in which the values in the source
data give indices into a fixed palette of color settings. Unpacking data in this format requires
two steps:  (1) reading and unpacking the palette in the source file, (2) performing a look-up
operation for each pixel to map the index value to a color.  A similar approach was used in
the original GIF specification and, checking wikipedia, it appears that it is also supported
by PNG and BMP.  TIFF files in this format are used extensively in mapping and Geographic
Information System implementation.
> The current inplementation of the PhotometicInterpreterPalette for TIFF files has an
inefficiency in that it performs the unpacking operation from step one each time a new pixel
is read. Thus, if a file contains three million red pixels, the byte-manipulation for the
color red is repeated three million times.  It would be more efficient for the PhotometricInterpreterPalette
class to perform the unpacking operation once, in its constructor. Since there are a maximum
of 256 colors in an 8-bit palette, this approach would require moderate use of memory.
> In time tests this approach reduced the reading time for a large TIFF file by about 13
percent (for details on the timing procedures, see Tracker Item 58):
> Unmodified Code:   1204.9 ms.
> After change:   1049.7 ms.

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