Crate vaster 

vaster

Raster grid logic, without any pesky data.

Raster grids are defined by dimension (ncol, nrow) and extent (xmin, xmax, ymin, ymax). Everything else — resolution, cell centres, geotransforms, cell indexing — derives from those six numbers.

This crate provides that derivation with zero dependencies.

Conventions

• Extent is [xmin, xmax, ymin, ymax] — same as the R vaster package
• Dimension is [ncol, nrow]
• Cell indices are 0-based (the R package uses 1-based)
• Geotransform follows GDAL convention: [origin_x, pixel_width, row_rotation, origin_y, col_rotation, pixel_height]
• Cell (0, 0) is the top-left pixel, traversing right then down

GDAL geotransform

The 6-element geotransform maps pixel coordinates to geographic coordinates:

x_geo = gt[0] + pixel * gt[1] + line * gt[2]
y_geo = gt[3] + pixel * gt[4] + line * gt[5]

For north-up images (no rotation): gt[2] == 0, gt[4] == 0, gt[5] < 0.

Reference: https://gdal.org/tutorials/geotransforms_tut.html

Quick start

use vaster::*;

let extent = [0.0, 360.0, -90.0, 90.0];
let dim = [360, 180];

// Build a geotransform
let gt = extent_dim_to_gt(&extent, &dim);
assert_eq!(gt[1], 1.0); // 1 degree per pixel

// Cell centre of top-left pixel
let (x, y) = xy_from_cell(&dim, &extent, 0);
assert!((x - 0.5).abs() < 1e-10);
assert!((y - 89.5).abs() < 1e-10);

// Which cell contains a point?
let cell = cell_from_xy(&dim, &extent, 10.3, 45.7);
assert_eq!(cell, Some(10 + 44 * 360));

Relationship to the R package

This crate is the Rust equivalent of hypertidy/vaster, an R package for raster grid logic. The API follows the same conventions with one difference: cell indices are 0-based in Rust (1-based in R).

Functions

cell_from_row_col

Cell index from 0-based (row, col).

cell_from_xy

Cell index from geographic (x, y) coordinates.

col_from_cell

Column index (0-based) from cell index.

col_from_x

Fractional column index from geographic x-coordinate.

col_row_from_xy

Fractional (col, row) from geographic (x, y), using the full affine inverse.

crop_offset

Compute the column and row offset of an aligned sub-grid within its parent.

extent_dim_to_gt

Build a geotransform from extent and dimensions.

geotransform_to_world

Convert a GDAL geotransform to world file parameters.

gt_to_extent

Extract extent from a geotransform and dimensions.

inv_geotransform

Invert a geotransform.

ncell

Total number of cells.

row_col_from_cell

(row, col) from cell index (both 0-based).

row_from_cell

Row index (0-based) from cell index.

row_from_y

Fractional row index from geographic y-coordinate.

vcrop

Snap an extent to align with a parent grid.

world_to_geotransform

Convert a world file to a GDAL geotransform.

x_centre

X-coordinates of cell centres for each column.

x_corner

X-coordinates of cell edges (corners) for each column boundary.

x_from_col

Geographic x-coordinate of a pixel column centre.

x_res

Resolution (pixel width) in the x direction.

xy_from_cell

Geographic (x, y) of a cell centre, from extent and dimension.

xy_from_col_row

Geographic (x, y) from pixel (col, row), using the full affine transform.

y_centre

Y-coordinates of cell centres for each row.

y_corner

Y-coordinates of cell edges (corners) for each row boundary.

y_from_row

Geographic y-coordinate of a pixel row centre.

y_res

Resolution (pixel height) in the y direction.

Type Aliases

Dimension

Raster dimensions: [ncol, nrow].

Extent

Raster extent: [xmin, xmax, ymin, ymax].

GeoTransform

A GDAL-style affine geotransform.

WorldFile

World file parameters: [x_res, y_skew, x_skew, y_res, x_centre, y_centre]