## ----include = FALSE----------------------------------------------------------
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

## ----setup--------------------------------------------------------------------
library(vaster)

## -----------------------------------------------------------------------------
dimension <- c(10, 5)
extent <- c(0, 10, 0, 5)

## Cell boundaries are at integers
x_corner(dimension, extent)
y_corner(dimension, extent)

## -----------------------------------------------------------------------------
user_extent <- c(2.3, 7.8, 1.2, 4.6)

## Snap outward (default) - includes all cells touched
align_extent(user_extent, dimension, extent, snap = "out")

## Snap inward - only fully contained cells
align_extent(user_extent, dimension, extent, snap = "in")

## Snap to nearest boundary
align_extent(user_extent, dimension, extent, snap = "near")

## -----------------------------------------------------------------------------
## Snap to 0.5 unit resolution
snap_extent(c(2.3, 7.8, 1.2, 4.6), res = 0.5)

## Snap to 1 unit resolution
snap_extent(c(2.3, 7.8, 1.2, 4.6), res = 1)

## -----------------------------------------------------------------------------
## Standard grid has origin at (0, 0)
origin(c(10, 5), c(0, 10, 0, 5))

## Offset grid
origin(c(10, 5), c(0.5, 10.5, 0.25, 5.25))

## -----------------------------------------------------------------------------
result <- vcrop(c(2.3, 7.8, 1.2, 4.6), dimension, extent)
result$extent
result$dimension

## -----------------------------------------------------------------------------
## Extent that partially overlaps
intersect_extent(c(-2, 5, -1, 3), dimension, extent)

## Extent fully within grid
intersect_extent(c(2, 8, 1, 4), dimension, extent)

## -----------------------------------------------------------------------------
crop_extent <- c(2, 8, 1, 4)

## Dimension of the cropped region
extent_dimension(crop_extent, dimension, extent)

## Verify: 6 columns (8-2) and 3 rows (4-1)

## -----------------------------------------------------------------------------
## Define source grid (e.g., from a large raster file)
src_dim <- c(3600, 1800)  # 0.1 degree global grid
src_ext <- c(-180, 180, -90, 90)

## User's region of interest
roi <- c(140, 155, -45, -30)  # Southeastern Australia

## Align to grid
aligned_roi <- align_extent(roi, src_dim, src_ext, snap = "out")
aligned_roi

## Get dimensions of cropped region
crop_dim <- extent_dimension(aligned_roi, src_dim, src_ext)
crop_dim

## Get cell indices to read
cells <- cell_from_extent(src_dim, src_ext, aligned_roi)
length(cells)

## Verify
crop_dim[1] * crop_dim[2]

## -----------------------------------------------------------------------------
## RasterIO parameters for reading the crop region
rio <- rasterio0(src_dim, src_ext, aligned_roi)
rio