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https://issues.apache.org/jira/browse/SANSELAN-57?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gary Lucas updated SANSELAN-57:
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Attachment: Sanselan-57-TiffMetadataWriter.patch
Patch tested successfully using existing unit tests.
> Add method to specify metadata (TiffOutputFields) when a new TIFF file is
> created
> ---------------------------------------------------------------------------------
>
> Key: SANSELAN-57
> URL: https://issues.apache.org/jira/browse/SANSELAN-57
> Project: Commons Sanselan
> Issue Type: Improvement
> Environment: All supported operating systems
> Reporter: Gary Lucas
> Attachments: Sanselan-57-TiffMetadataWriter.patch
>
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> I propose to add a new method to the TiffImageWriterBase class that will
> simplify the process of adding metadata tags (any kind, not just the
> geographic ones) to a TIFF file when it is created. I have a version of this
> class ready for uploading, and will do so in a day or two if nobody has any
> suggestions for alternatives.
> The rationale for this new feature grows from a requirement to produce
> GeoTIFF files. GeoTIFF's are a widely supported industry standard that takes
> advantage of the fact that TIFF files permit the use of supplemental metadata
> tags (TIFF's equivalent to EXIF tags). The GeoTIFF tags feature metadata
> that allows the TIFF file to be tied to images of maps, convert pixels to
> latitude/longitude coordinates, etc.
> Although Sanselan does provide an API that allows an application to add such
> tags to an existing image (TiffImageWriterLossy), this approach requires
> writing the TIFF file twice. Since some GeoTIFF's can be quite large (50
> megs is common), this is a suboptimal approach. An API that permits the file
> to be written just once would be preferred.
> The new method will a variation of writeImage that includes an array list of
> TiffOutputFields:
> writeImage(BufferedImage src, OutputStream os, Map params, ArrayList
> applicationSuppliedFieldList)
> When the initial TIFF file header is created, Sanselan currently adds a
> "directory" to the beginning of the file ("directory" is the term used in the
> TIFF format specification to mean, simply, a collection of data). This
> directory provides image metadata such as width, height, etc. The new method
> will add application-supplied output fields to the initial directory. This
> approach will have the advantage that an application will be able to obtain
> metadata for a GeoTIFF file without actually reading the full body of the
> image. It will also permit the creating of GeoTIFFs consistent with those
> being produced by the U.S. Geological Survey and other agencies that provide
> a complete set of geographic information in the first directory in the file.
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