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Converting raster images to XML and SVG

Converting raster images to XML and SVG. The potential of XML - encoded images and SVG image files in Geomatics. Contents. Problem Statement The conversion of raster images to XML code Converting raster images to SVG code The benefits to Geomatics Drawbacks Conclusions.

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Converting raster images to XML and SVG

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  1. Converting raster images to XML and SVG The potential of XML - encoded images and SVG image files in Geomatics

  2. Contents • Problem Statement • The conversion of raster images to XML code • Converting raster images to SVG code • The benefits to Geomatics • Drawbacks • Conclusions

  3. Problem Statement • Image information is stored in a tabular way and each pixel usually preserves three values in a range between 0-255. • In an aerial photo or a satellite image, each pixel represent the reflection of the earth. • Each material reflects sun beams in its own way. • There is a very precise photogrametric process which can register an image to real world coordinates.

  4. Problem Statement • So, for Geomatics, what really matters in raster images are: a. Separate pixel values for every recording band b. Geometric information for each pixel

  5. Problem Statement normal color color infrared The football field has artificial turf with low near-infrared reflectance. That is why in normal color photo the whole region appears with green color and in the color infrared photo the real vegetation is red and the artificial black.

  6. The conversion of raster images to XML code STEPS: • Use any programming language to segregate pixel values in their components • Create the XML file putting each value in a different XML element • Create the XML schema for the above XML file.

  7. The conversion of raster images to XML code <?xml version="1.0" encoding="UTF-8"?> <image> <pixel id="0" row="0" column="0"> <r>201</r> <g>171</g> <b>81</b> </pixel> <pixel id="1" row="0" column="1"> <r>203</r> <g>175</g> <b>78</b> </pixel> ............ </image>

  8. Converting raster images to SVG code • The tabular structure of the raster format is reproduced with an array of <rect> elements • The size of each <rect> element is set to 1px. • The rendering of each rectangle is the same as the equivalent pixel in the raster image. • Geometric information relates to: • relative position of each rectangle inside the array • absolute position of each rectangle in real world coordinates.

  9. Converting raster images to SVG code • A very important issue is the way that rendering information should be stored in an SVG image file. • The size of each <rect> element is set to 1px. • The rendering of each rectangle is the same as the equivalent pixel in the raster image. • Geometric information relates to: • relative position of each rectangle inside the array • absolute position of each rectangle in real world coordinates.

  10. The benefits to Geomatics • XML - encoded images could serve the storage of all kind of raster data : • three-band images. • multi-spectral images. • satellite scenes. • XSLT has all the necessary programming tools needed to carry out the manipulation of the XML-encoded images such as: • classification algorithms. • region growing algorithms.

  11. The benefits to Geomatics The potential of XML based Images and SVG Image files in Geomatics, Step 1.

  12. The benefits to Geomatics • SVG image files have the advantage of the segregated pixel values along with the ability to display the result of every change imposed on them. • The use of XSLT in this case could be the equivalent of applying either image processing filters or geo-reference transformations

  13. The benefits to Geomatics The potential of XML based Images and SVG Image files in Geomatics, Step 2

  14. Drawbacks • Large files: The method creates large files due to the analytical recording of information. But the use of compressed XML and SVG files gives approximately 2,5 times larger files than the original raster datasets. • Time: There is considerable delay in the rendering of the SVG image files. Any SVG viewer should read a CSS instruction for every <rect> element in the file.

  15. Conclusions • The transformation of raster images into XML encoding, apart from changing the way files are stored, contributes substantially to the way users interact with real data. • The created files are enriched with qualitative information, which can be further exploited by the user. • In the domain of Geomatics the knowledge of both geometry and attribute information is indispensable for further processing and utilization of spatial data.

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