Struct RasterCalculator 

pub struct RasterCalculator;

Raster calculator for map algebra with expression parsing

Implementations

impl RasterCalculator

pub fn evaluate_bytecode( expr_str: &str, bands: &[RasterBuffer], ) -> Result<RasterBuffer>

Evaluate a band-math expression using the bytecode VM.

Parsing and compilation happen once; the resulting CompiledProgram is then executed for every pixel with a pair of pre-allocated scratch buffers (cache and stack) so no heap allocations occur inside the pixel loop.

This method is functionally equivalent to RasterCalculator::evaluate but can be 2–5× faster on large rasters because it avoids AST tree traversal per pixel.

Arguments

• expr_str – The expression string (e.g. "(B1 - B2) / (B1 + B2)").
• bands – Input RasterBuffer slices; B1 = bands[0], B2 = bands[1], …

Errors

Returns an AlgorithmError if:

• bands is empty (AlgorithmError::EmptyInput),
• band dimensions differ (AlgorithmError::InvalidDimensions),
• the expression cannot be parsed or compiled.

impl RasterCalculator

pub fn evaluate( expression: &str, bands: &[RasterBuffer], ) -> Result<RasterBuffer>

Evaluates a raster expression on one or more bands

Arguments

• expression - The expression to evaluate (e.g., “(B1 - B2) / (B1 + B2)”)
• bands - Input bands (B1, B2, etc.)

Examples

NDVI: "(B1 - B2) / (B1 + B2)" Conditional: "if B1 > 100 then B1 * 2 else B1" Math: "sqrt(B1 ^ 2 + B2 ^ 2)"

Errors

Returns an error if the expression is invalid or evaluation fails

pub fn evaluate_parallel( expression: &str, bands: &[RasterBuffer], ) -> Result<RasterBuffer>

Evaluates a raster expression in parallel using rayon

This method processes rows in parallel for improved performance on multi-core systems. Falls back to sequential evaluation if the parallel feature is not enabled.

Arguments

• expression - The expression to evaluate (e.g., “(B1 - B2) / (B1 + B2)”)
• bands - Input bands (B1, B2, etc.)

Examples

NDVI: "(B1 - B2) / (B1 + B2)" Conditional: "if B1 > 100 then B1 * 2 else B1" Math: "sqrt(B1 ^ 2 + B2 ^ 2)"

Errors

Returns an error if the expression is invalid or evaluation fails

pub fn apply_binary( a: &RasterBuffer, b: &RasterBuffer, op: RasterExpression, ) -> Result<RasterBuffer>

Applies a binary operation to two rasters (legacy API)

pub fn apply_unary<F>(src: &RasterBuffer, func: F) -> Result<RasterBuffer>

where F: Fn(f64) -> f64,

Applies a unary function to a raster (legacy API)