Hi, This is a call for discussion for "RFC 45: GDAL datasets and raster bands as virtual memory mappings"
Beginning of the RFC inline (the full RFC includes a few colorful schemas !) : """ == Summary == This document proposes additions to GDAL so that image data of GDAL datasets and raster bands can be seen as virtual memory mappings, for hopefully simpler usage. == Rationale == When one wants to read or write image data from/into a GDAL dataset or raster band, one must use the RasterIO() interface for the regions of interest that are read or written. For small images, the most convenient solution is usually to read/write the whole image in a single request where the region of interest is the full raster extent. For larger images, particularly when they do not fit entirely in RAM, this is not possible, and if one wants to operate on the whole image, one must use a windowing strategy to avoid memory issues : typically by proceeding scanline (or group of scanlines) by scanline, or by blocks for tiled images. This can make the writing of algorithms more complicated when they need to access a neighbourhoud of pixels around each pixel of interest, since the size of this extra window must be taken into account, leading to overlapping regions of interests. Nothing that cannot be solved, but that requires some additional thinking that distracts from the followed main purpose. The proposed addition of this RFC is to make the image data appear as a single array accessed with a pointer, without being limited by the size of RAM with respect to the size of the dataset (excepted limitations imposed by the CPU architecture and the operating system) """ Best regards, Even -- Geospatial professional services http://even.rouault.free.fr/services.html _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
