Converting raster images to XML and SVG

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
lt?xml version"1.0" encoding"UTF-8"?gt ltimagegt
ltpixel id"0" row"0" column"0"gt ltrgt201lt/rgt
ltggt171lt/ggt ltbgt81lt/bgt lt/pixelgt ltpixel
id"1" row"0" column"1"gt ltrgt203lt/rgt
ltggt175lt/ggt ltbgt78lt/bgt lt/pixelgt ...........
. lt/imagegt
8
Converting raster images to SVG code

• The tabular structure of the raster format is
  reproduced with an array of ltrectgt elements
• The size of each ltrectgt 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 ltrectgt 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 ltrectgt 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.