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89 lines
2.5 KiB
Markdown
89 lines
2.5 KiB
Markdown
# GDAL Raster GeoTIFF Workflow
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```
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Build Tools: CMake/Ninja
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OS: Linux
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```
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### For installing GDAL:
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```
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sudo apt-get install python3.6-dev
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sudo add-apt-repository ppa:ubuntugis/ppa && sudo apt update
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sudo apt-get install gdal-bin
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sudo apt-get install libgdal-dev
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```
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### Dependencies:
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PNG: `sudo apt-get install libpng-dev`
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PCRE: `sudo apt-get install libpcre3 libpcre3-dev`
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PROJ: `sudo apt-get install libproj-dev`
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OBS! You may need to set `export LD_LIBRARY_PATH=/lib:/usr/lib:/usr/local/lib`.
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It is required for libproj.so to be found into /usr/local/lib/. You can also fix
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this by typing `locate libproj.so` which will give you
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<the_absolute_libproj.so_path> and then `cp <the_absolute_libproj.so_path>
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/usr/local/lib/`.
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### Initializing GDAL submodule:
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`git submodule add https://github.com/OSGeo/gdal/tree/master/gdal`
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### Building GDAL statically
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GNUmakefile from gdal/gdal can handle building the static library.
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`cd gdal/gdal && make static-lib`
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`cd ../.. && mkdir lib`
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`cp gdal/gdal/libgdal.a lib/`
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OBS! The file is huge! It may take a while.
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### For testing:
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`mkdir build && cd build`
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`cmake .. -G Ninja`
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`ninja`
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`./raster <your_absolute_tiff_file_path>`
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## About the project
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GDAL is a translator library for raster and vector geospatial data format. The
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project consist in rastering a GeoTIFF file format using GDAL functionalities
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and sandboxed methods.
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## Implementation
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*Sandboxing...*
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The purpose of sandboxing is to limit the permissions and capabilities of
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library’s methods, in order to secure the usage of them. After obtaining the
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sandbox, the functions will be called through an Sandbox API (being called api
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in the current test) and so, the operations, system calls or namspaces access
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may be controlled.
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*Raster process...*
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Useful functions from the `gdal.h` header are added to the SAPI library built
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with CMake.
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One .tiff file is manipulated with GDALOpen functionality, which extracts a
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pointer to the data set containg a list of raster bands, all pertaining to the
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same area. Metadata, a coordinate system, a georeferencing transform, size of
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raster and various other information are kept into the data set that corresponds
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to the image.
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To create an array containing the image information, the dimentions needed are
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extracted using some specific GDAL(X/Y)Size functions applied to the block.
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GDALRasterBand function takes care of data type conversion, one more step
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following: placing the converted data (with RasterIO method) into the created
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and well allocated structure.
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